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Fiedler J. 1120
THEORY OF COLOURS .
 GOETHE'S

THEORY OF COLOURS ;

TRANSLATED FROM THE GERMAN :

WITH NOTES BY

CHARLES LOCK EASTLAKE, R.A. , F.R.S.

" Cicero varietatem propriè in coloribus nasci, hinc in alienum migrare existimavit.
Certè non alibi natura copiosius aut majore lasciviâ opes suas commendavit. Metalla,
gemmas, marmora, flores, astra, omnia denique quæ progenuit suis etiam coloribus dis
tinxit ; ut venia debeatur si quis in tam numerosâ rerum sylvâ caligaverit."
CELIO CALCAONINI,

LONDON :
JOHN MURRAY, ALBEMARLE STREET.

1840.
 LONDON :
Printed by WILLIAM CLOWES and SONS,
Stamford Street.
INSTITU

L
O
h R

UNIVERSITY

1 .. JUN. 1941

OF OKFORD V
O
N
 ΤΟ

JEREMIAH HARMAN , Esq.

DEAR SIR,

I dedicate to you the following translation as a

testimony of my sincere gratitude and respect ; in doing so, I
but follow the example of Portius , an Italian writer, who in-
scribed his translation of Aristotle's Treatise on Colours to one of
the Medici.
I have the honour to be,
Dear Sir,

Your most obliged and obedient Servant,

C. L. EASTLAKE .
 THE

TRANSLATOR'S PREFACE .

ENGLISH writers who have spoken of Goethe's

" Doctrine of Colours , "* have generally con

fined their remarks to those parts of the work

in which he has undertaken to account for the

colours of the prismatic spectrum , and of re

fraction altogether, on principles different from

the received theory of Newton . The less ques

tionable merits of the treatise consisting of a

well- arranged mass of observations and experi

ments, many of which are important and inter

esting, have thus been in a great measure over

looked . The translator, aware of the opposition
which the theoretical views alluded to have met

with, intended at first to make a selection of

* " Farbenlehre ” -in the present translation generally rendered

" Theory of Colours. "
viii TRANSLATOR'S PREFACE .

such of the experiments as seem more directly

applicable to the theory and practice of paint

ing. Finding , however, that the alterations this
would have involved would have been incom

patible with a clear and connected view of the

author's statements , he preferred giving the

theory itself entire, reflecting , at the same time,

that some scientific readers may be curious to

hear the author speak for himself even on the

points at issue.

In reviewing the history and progress of his

opinions and researches, Goethe tells us that he

first submitted his views to the public in two

short essays entitled " Contributions to Optics ."

Among the circumstances which he supposes
were unfavourable to him on that occasion , he

mentions the choice of his title, observing that

by a reference to optics he must have appeared

to make pretensions to a knowledge of mathe

matics, a science with which he admits he was

very imperfectly acquainted . Another cause to

which he attributes the severe treatment he ex

perienced, was his having ventured so openly to

question the truth of the established theory :

but this last provocation could not be owing to

mere inadvertence on his part ; indeed the larger

work, in which he alludes to these circum
 TRANSLATOR'S PREFACE . ix

stances, is still more remarkable for the violence

of his objections to the Newtonian doctrine .

There can be no doubt, however, that much

of the opposition Goethe met with was to be

attributed to the manner as well as to the sub

stance of his statements . Had he contented

himself with merely detailing his experiments

and showing their application to the laws of

chromatic harmony, leaving it to others to re
concile them as they could with the pre-estab

lished system , or even to doubt in consequence,

the truth of some of the Newtonian conclusions,

he would have enjoyed the credit he deserved

for the accuracy and the utility of his investi
gations. As it was, the uncompromising ex

pression of his convictions only exposed him to

the resentment or silent neglect of a great por

tion of the scientific world , so that for a time he

could not even obtain a fair hearing for the less

objectionable or rather highly valuable commu

nications contained in his book . A specimen

of his manner of alluding to the Newtonian

theory will be seen in the preface.

It was quite natural that this spirit should

call forth a somewhat vindictive feeling, and

with it not a little uncandid as well as unspar
ing criticism . " The Doctrine of Colours" met
 X

.
PREFACE
TRANSLATOR'S
with this reception in Germany long before it
was noticed in England, where a milder and
fairer treatment could hardly be expected , espe-

cially at a time when, owing perhaps to the

limited intercourse with the continent, German

literature was far less popular than it is at pre-

sent. This last fact, it is true , can be of little

importance in the present instance, for although

the change of opinion with regard to the genius

of an enlightened nation must be acknowledged

to be beneficial , it is to be hoped there is no

fashion in science, and the translator begs to

state once for all, that in advocating the ne-

glected merits of the " Doctrine of Colours ," he

is far from undertaking to defend its imputed

errors . Sufficient time has, however, now

elapsed since the publication of this work (in

1810 ) to allow a calmer and more candid exami-

nation of its claims . In this more pleasing task

Germany has again for some time led the way,

and many scientific investigators have followed

up the hints and observations of Goethe with a

due acknowledgment of the acuteness of his

views . *

Sixteen years after the appearance of the Farbenlehre, Dr.

Johannes Müller devoted a portion of his work, " Zur vergleich-
enden Physiologie des Gesichtssinnes des Menschen und der
 TRANSLATOR'S PREFACE. xi

It may require more magnanimity in English

scientific readers to do justice to the merits of

one who was so open and, in many respects,

it is believed , so mistaken an opponent of

Newton ; but it must be admitted that the

statements of Goethe contain more useful prin

ciples in all that relates to harmony of colour

than any that have been derived from the esta

blished doctrine. It is no derogation of the

more important truths of the Newtonian theory

to say, that the views it contains seldom appear

in a form calculated for direct application to the

arts. The principle of contrast, so universally

exhibited in nature, so apparent in the action

and re-action of the eye itself, is scarcely hinted

at. The equal pretensions of seven colours, as

Thiere," to the critical examination of Goethe's theory. In his

introductory remarks he expresses himself as follows-" For my
own part I readily acknowledge that I have been greatly indebted
to Goethe's treatise, and can truly say that without having studied
it for some years in connexion with the actual phenomena, the pre
sent work would hardly have been undertaken . I have no hesitation
in confessing more particularly that I have full faith in Goethe's
statements, where they are merely descriptive of the phenomena,
and where the author does not enter into explanations involving
a decision on the great points of controversy ." The names of
Hegel, Schelling, Seebeck, Steffens, may also be mentioned, and
many others might be added , as authorities more or less favourable
to the Farbenlehre.
xii TRANSLATOR'S PREFACE.

such, and the fanciful analogies which their

assumed proportions could suggest, have rarely
found favour with the votaries of taste,-indeed

they have long been abandoned even by

scientific authorities . * And here the trans

lator stops he is quite aware that the defects

which make the Newtonian theory so little

available for æsthetic application , are far from
invalidating its more important conclusions in

the opinion of most scientific men . In carefully

abstaining therefore from any comparison be

tween the two theories in these latter respects ,

he may still be permitted to advocate the clear

ness and fulness of Goethe's experiments . The

German philosopher reduces the colours to their

* "When Newton attempted to reckon up the rays of light

decomposed by the prism," says Sir John Leslie, " and ventured
to assign the famous number seven, he was apparently influenced
by some lurking disposition towards mysticism. If any unpreju
diced person will fairly repeat the experiment, he must soon be
convinced that the various coloured spaces which paint the spec 1
trum slide into each other by indefinite shadings : he may name
four or five principal colours, but the subordinate spaces are evi
dently so multiplied as to be incapable of enumeration . The
same illustrious mathematician , we can hardly doubt, was be
trayed by a passion for analogy, when he imagined that the pri
mary colours are distributed over the spectrum after the proportions
of the diatonic scale of music, since those intermediate spaces have
really no precise and defined limits. " -Treatises on Various
Subjects of Natural and Chemical Philosophy, p . 59.
 TRANSLATOR'S PREFACE . xiii

origin and simplest elements ; he sees and con-

stantly bears in mind, and sometimes ably

elucidates, the phenomena of contrast and gra-

dation, two principles which may be said to

make up the artist's world , and to constitute the

chief elements of beauty. These hints occur

mostly in what may be called the scientific part

of the work. On the other hand , in the portion

expressly devoted to the æsthetic application of

the doctrine , the author seems to have made but

an inadequate use of his own principles .

In that part of the chapter on chemical co-

lours which relates to the colours of plants and

animals, the same genius and originality which

are displayed in the Essays on Morphology , and

which have secured to Goethe undisputed rank

among the investigators of nature, are frequently

apparent.
But one of the most interesting features of
Goethe's theory, although it cannot be a recom-

mendation in a scientific point of view, is , that

it contains, undoubtedly with very great im-

provements, the general doctrine of the ancients
and of the Italians at the revival of letters .
The translator has endeavoured , in some notes ,

to point out the connexion between this theory

and the practice of the Italian painters .

xiv TRANSLATOR'S PREFACE .

The " Doctrine of Colours," as first published

in 1810, consists of two volumes in 8vo. , and

sixteen plates , with descriptions , in 4to . It is

divided into three parts, a didactic , a contro

versial, and an historical part ; the present

translation is confined to the first of these, with

such extracts from the other two as seemed

necessary, in fairness to the author, to explain

some of his statements . The polemical and

historical parts are frequently alluded to in the

preface and elsewhere in the present work, but
it has not been thought advisable to omit these
allusions . No alterations whatever seem to

have been made by Goethe in the didactic por

tion in later editions , but he subsequently wrote

an additional chapter on entoptic colours , ex

pressing his wish that it might be inserted in

the theory itself at a particular place which he

points out. The form of this additional essay

is, however, very different from that of the rest

of the work , and the translator has therefore

merely given some extracts from it in the ap

pendix . The polemical portion has been more
than once omitted in later editions .

In the two first parts the author's statements

are arranged numerically, in the style of Bacon's

Natural History. This, we are told , was for the

 TRANSLATOR'S PREFACE . XV

convenience of reference ; but many passages

are thus separately numbered which hardly

seem to have required it. The same arrange

ment is, however, strictly followed in the trans

lation to facilitate a comparison with the original

where it may be desired ; and here the translator
observes, that although he has sometimes per

mitted himself to make slight alterations, in

order to avoid unnecessary repetition, or to

make the author's meaning clearer, he feels

that an apology may rather be expected from

him for having omitted so little . He was scru

pulous on this point, having once determined to

translate the whole treatise, partly, as before

stated, from a wish to deal fairly with a con

troversial writer, and partly because many pas

sages, not directly bearing on the scientific

views, are still characteristic of Goethe. The
observations which the translator has ventured

to add are inserted in the appendix : these ob

servations are chiefly confined to such of the

author's opinions and conclusions as have direct

reference to the arts ; they seldom interfere with

the scientific propositions, even where these

have been considered most vulnerable.
1
1
 PREFACE TO THE FIRST EDITION

OF 1810 .

Ir may naturally be asked whether, in proposing

to treat of colours , light itself should not first

engage our attention to this we briefly and

frankly answer that since so much has already

been said on the subject of light, it can hardly

be desirable to multiply repetitions by again

going over the same ground.

Indeed, strictly speaking, it is useless to at-
tempt to express the nature of a thing abstract-

edly. Effects we can perceive, and a complete

history of those effects would , in fact, sufficiently

define the nature of the thing itself. We should

try in vain to describe a man's character, but let

his acts be collected and an idea of the character

will be presented to us .

The colours are acts of light ; its active and

passive modifications : thus considered we may

expect from them some explanation respecting

light itself. Colours and light, it is true, stand
in the most intimate relation to each other, but
b
xviii PREFACE TO THE FIRST EDITION.

we should think of both as belonging to nature

as a whole, for it is nature as a whole which

manifests itself by their means in an especial

manner to the sense of sight.

The completeness of nature displays itself to

another sense in a similar way . Let the eye be

closed, let the sense of hearing be excited , and

from the lightest breath to the wildest din, from

the simplest sound to the highest harmony,

from the most vehement and impassioned cry
to the gentlest word of reason, still it is Nature

that speaks and manifests her presence, her

power, her pervading life and the vastness of

her relations ; so that a blind man to whom the

infinite visible is denied, can still comprehend

an infinite vitality by means of another organ .

And thus as we descend the scale of being,

Nature speaks to other senses- to known , mis

understood, and unknown senses : so speaks she

with herself and to us in a thousand modes . To

the attentive observer she is nowhere dead nor

silent ; she has even a secret agent in inflexible

matter, in a metal, the smallest portions of which

tell us what is passing in the entire mass . How

ever manifold, complicated , and unintelligible

this language may often seem to us, yet its ele

ments remain ever the same. With light poise
 PREFACE TO THE FIRST EDITION. xix

and counterpoise, Nature oscillates within her

prescribed limits, yet thus arise all the varieties

and conditions of the phenomena which are

presented to us in space and time.

Infinitely various are the means by which we

become acquainted with these general move

ments and tendencies : now as a simple repul

sion and attraction, now as an upsparkling and

vanishing light, as undulation in the air, as com

motion in matter, as oxydation and deoxydation ;

but always, uniting or separating, the great pur

pose is found to be to excite and promote exist

ence in some form or other.

The observers of nature finding, however,

that this poise and counterpoise are respectively

unequal in effect, have endeavoured to repre

sent such a relation in terms . They have every

where remarked and spoken of a greater and

lesser principle, an action and resistance , a

doing and suffering, an advancing and retiring ,
a violent and moderating power ; and thus a

symbolical language has arisen , which, from

its close analogy, may be employed as equiva

lent to a direct and appropriate terminology .

To apply these designations, this language of

Nature to the subject we have undertaken ; to

enrich and amplify this language by means of
b 2
XX PREFACE TO THE FIRST EDITION .

the theory of colours and the variety of their

phenomena, and thus facilitate the communica-

tion of higher theoretical views, was the prin-

cipal aim of the present treatise.

The work itself is divided into three parts .

The first contains the outline of a theory of

colours . In this , the innumerable cases which

present themselves to the observer are collected

under certain leading phenomena, according to

an arrangement which will be explained in the

Introduction ; and here it may be remarked , that

although we have adhered throughout to experi-

ment, and throughout considered it as our basis,

yet the theoretical views which led to the ar-

rangement alluded to, could not but be stated.

It is sometimes unreasonably required by per-

sons who do not even themselves attend to

such a condition, that experimental information

should be submitted without any connecting

theory to the reader or scholar, who is himself

to form his conclusions as he may list. Surely

the mere inspection of a subject can profit us

but little. Every act of seeing leads to consi-
deration, consideration to reflection , reflection

to combination, and thus it may be said that in

every attentive look on nature we already theo-

rise . But in order to guard against the possible

 PREFACE TO THE FIRST EDITION. xxi

abuse of this abstract view, in order that the

practical deductions we look to should be really

useful, we should theorise without forgetting

that we are so doing, we should theorise with

mental self- possession , and, to use a bold word,

with irony .

In the second part* we examine the New

tonian theory ; a theory which by its ascend

ancy and consideration has hitherto impeded a

free inquiry into the phenomena of colours . We

combat that hypothesis, for although it is no

longer found available, it still retains a tradi

tional authority in the world . Its real relations

to its subject will require to be plainly pointed

out ; the old errors must be cleared away, if the

theory of colours is not still to remain in the rear

of so many other better investigated depart

ments of natural science . Since, however, this

second part of our work may appear somewhat

dry as regards its matter, and perhaps too vehe
ment and excited in its manner, we may here

be permitted to introduce a sort of allegory in

a lighter style, as a prelude to that graver por

tion , and as some excuse for the earnestness
alluded to .

We compare the Newtonian theory of colours

* The Polemical part.

xxii PREFACE TO THE FIRST EDITION.

to an old castle, which was at first constructed

by its architect with youthful precipitation ; it

was, however, gradually enlarged and equipped
by him according to the exigencies of time and
circumstances, and moreover was still further

fortified and secured in consequence of feuds

and hostile demonstrations .

The same system was pursued by his succes-

sors and heirs their increased wants within ,

the harassing vigilance of their opponents with-

out, and various accidents compelled them in

some places to build near, in others in con-
nexion with the fabric , and thus to extend the

original plan .
It became necessary to connect all these in-

congruous parts and additions by the strangest

galleries, halls and passages . All damages ,
whether inflicted by the hand of the enemy or
the power of time, were quickly made good. As

occasion required , they deepened the moats,

raised the walls , and took care there should be

no lack of towers, battlements , and embrasures .

This care and these exertions gave rise to a pre-

judice in favour of the great importance of the

fortress, and still upheld that prejudice, although

the arts of building and fortification were by

this time very much advanced , and people had
 PREFACE TO THE FIRST EDITION. xxiii

learnt to construct much better dwellings and

defences in other cases . But the old castle

was chiefly held in honour because it had

never been taken, because it had repulsed so

many assaults , had baffled so many hostile

operations, and had always preserved its virgin

renown . This renown , this influence lasts even
now it occurs to no one that the old castle is

become uninhabitable . Its great duration , its

costly construction , are still constantly spoken

of. Pilgrims wend their way to it ; hasty

sketches of it are shown in all schools, and it is

thus recommended to the reverence of suscep

tible youth . Meanwhile, the building itself is

already abandoned ; its only inmates are a few

invalids , who in simple seriousness imagine that

they are prepared for war.

Thus there is no question here respecting a

tedious siege or a doubtful war ; so far from it

we find this eighth wonder of the world already

nodding to its fall as a deserted piece of anti

quity, and begin at once, without further cere

mony, to dismantle it from gable and roof

downwards ; that the sun may at last shine into

the old nest of rats and owls, and exhibit to the

eye of the wondering traveller that labyrinthine,

incongruous style of building , with its scanty,

xxiv PREFACE TO THE FIRST EDITION .

make-shift contrivances, the result of accident

and emergency, its intentional artifice and

clumsy repairs . Such an inspection will, how

ever, only be possible when wall after wall, arch

after arch, is demolished, the rubbish being at

once cleared away as well as it can be.

To effect this, and to level the site where it is

possible to do so, to arrange the materials thus

acquired, so that they can be hereafter again

employed for a new building, is the arduous

duty we have undertaken in this Second Part.

Should we succeed , by a cheerful application of

all possible ability and dexterity, in razing this

Bastille, and in gaining a free space , it is thus

by no means intended at once to cover the site

again and to encumber it with a new structure ;

we propose rather to make use of this area for

the purpose of passing in review a pleasing and

varied series of illustrative figures .
I
The third part is thus devoted to the histo

rical account of early inquirers and investiga

As we before expressed the opinion that

the history of an individual displays his cha

racter, so it may here be well affirmed that the

history of science is science itself. We cannot

clearly be aware of what we possess till we have

the means of knowing what others possessed

 PREFACE TO THE FIRST EDITION. XXV

before us . We cannot really and honestly re

joice in the advantages of our own time if we

know not how to appreciate the advantages of

former periods . But it was impossible to write ,

or even to prepare the way for a history of the

theory of colours while the Newtonian theory

existed ; for noaristocratic presumption has

ever looked down on those who were not of its

order, with such intolerable arrogance as that

betrayed by the Newtonian school in deciding

on all that had been done in earlier times and

all that was done around it . With disgust and

indignation we find Priestley , in his History of

Optics , like many before and after him , dating

the success of all researches into the world of

colours from the epoch of a decomposed ray

of light , or what pretended to be so ; looking

down with a supercilious air on the ancient and

less modern inquirers , who , after all , had pro

ceeded quietly in the right road , and who have

transmitted to us observations and thoughts in

detail which we can neither arrange better nor

conceive more justly.

We have a right to expect from one who pro

poses to give the history of any science, that he

inform us how the phenomena of which it treats

were gradually known, and what was imagined ,
xxvi PREFACE TO THE FIRST EDITION .

conjectured, assumed, or thought respecting

them. To state all this in due connexion is by

no means an easy task ; need we say that to

write a history at all is always a hazardous

affair ; with the most honest intention there is

always a danger of being dishonest ; for in such

an undertaking, a writer tacitly announces at

the outset that he means to place some things

in light, others in shade. The author has ,

nevertheless , long derived pleasure from the

prosecution of his task : but as it is the in

tention only that presents itself to the mind

as a whole, while the execution is gene

rally accomplished portion by portion, he is

compelled to admit that instead of a history

he furnishes only materials for one. These

materials consist in translations , extracts, ori

ginal and borrowed comments, hints, and notes ;

a collection , in short, which , if not answering
all that is required , has at least the merit of

having been made with earnestness and inte

rest. Lastly, such materials , -not altogether

untouched it is true, but still not exhausted,

may be more satisfactory to the reflecting reader

in the state in which they are, as he can easily

combine them according to his own judgment.

This third part, containing the history of the

1
 PREFACE TO THE FIRST EDITION. xxvii

science, does not, however, thus conclude the

subject : a fourth supplementary portion* is

added . This contains a recapitulation or revi
sion ; with a view to which, chiefly, the para

graphs are headed numerically . In the execu

tion of a work of this kind some things may be

forgotten, some are of necessity omitted , so as

not to distract the attention , some can only be
arrived at as corollaries , and others may require

to be exemplified and verified : on all these ac

counts, postscripts, additions and corrections

are indispensable. This part contains , besides ,

some detached essays ; for example, that on the

atmospheric colours ; for as these are introduced

in the theory itself without any classification ,

they are here presented to the mind's eye at

one view. Again , if this essay invites the reader

to consult Nature herself, another is intended to

recommend the artificial aids of science by cir

cumstantially describing the apparatus which

will in future be necessary to assist researches

into the theory of colours.

In conclusion , it only remains to speak of the

* This preface must have been written before the work was
finished, for at the conclusion of the historical part there is only
an apology for the non -appearance of the supplement here al
luded to.
Xxviii PREFACE TO THE FIRST EDITION.

plates which are added at the end of the work ; *

and here we confess we are reminded of that

incompleteness and imperfection which the

present undertaking has, in common with all

others of its class ; for as a good play can be in

fact only half transmitted to writing, a great

part of its effect depending on the scene, the

personal qualities of the actor, the powers of

his voice, the peculiarities of his gestures, and

even the spirit and favourable humour of the

spectators ; so it is , in a still greater degree,

with a book which treats of the appearances of

nature. To be enjoyed , to be turned to account,

Nature herself must be present to the reader,

either really, or by the help of a lively imagina

tion. Indeed, the author should in such cases
communicate his observations orally, exhibiting

the phenomena he describes-as a text, in the

first instance, -partly as they appear to us un

sought, partly as they may be presented by

contrivance to serve in particular illustration .

Explanation and description could not then fail

to produce a lively impression .

The plates which generally accompany works

like the present are thus a most inadequate sub

* In the present translation the necessary plates accompany

the text.
 PREFACE TO THE FIRST EDITION. xxix

stitute for all this ; a physical phenomenon

exhibiting its effects on all sides is not to be

arrested in lines nor denoted by a section . No

one ever dreams of explaining chemical expe

riments with figures ; yet it is customary in

physical researches nearly allied to these, be

cause the object is thus found to be in some

degree answered . In many cases , however, such

diagrams represent mere notions ; they are sym

bolical resources, hieroglyphic modes of com
munication , which by degrees assume the place
of the phenomena and of Nature herself, and

thus rather hinder than promote true know

ledge. In the present instance we could not

dispense with plates, but we have endeavoured

so to construct them that they may be confi

dently referred to for the explanation of the

didactic and polemical portions. Some of these

may even be considered as forming part of the

apparatus before mentioned .

We now therefore refer the reader to the

work itself; first, only repeating a request

which many an author has already made in

vain, and which the modern German reader,
—
especially, so seldom grants :

Si quid novisti rectius istis

Candidus imperti ; si non, his utere mecum .
DIRECTIONS FOR PLACING THE PLATES .

Plate 1 to face page . 6

2 ditto 82

3 ditto • 107

4 ditto • 136
 CONTENTS .

PAGE
Introduction xxxvii

PART I.
PHYSIOLOGICAL COLOURS .

I. Effects of Light and Darkness on the Eye · 2

II. Effects of Black and White Objects on the Eye 5
III. Grey Surfaces and Objects · 14
IV. Dazzling Colourless Objects 16
V. Coloured Objects • 20
VI. Coloured Shadows 29
VII. Faint Lights · 38
VIII. Subjective Halos • 40
Pathological Colours- Appendix 45

PART II .
PHYSICAL COLOURS .
659

IX. Dioptrical Colours

X. Dioptrical Colours of the First Class 60
XI. Dioptrical Colours of the Second Class - Re-
fraction • 74
Subjective Experiments . · 80
XII. Refraction without the Appearance of Colour ib.
XIII. Conditions of the Appearance of Colour • 81
XIV. Conditions under which the Appearance of Co-
lour increases • 86
XV. Explanation of the foregoing Phenomenal • 90
XVI. Decrease of the Appearance of Colour . 100
XVII . Grey Objects displaced by Refraction • 103
XVIII. Coloured Objects displaced by Refraction 106
XIX . Achromatism and Hyperchromatism . 118
xxxii CONTENTS .
PAGE
XX. Advantages of Subjective Experiments-
Transition to the Objective • 123
• 125
Objective Experiments
XXI. Refraction without the Appearance of Colour 127
XXII. Conditions of the Appearance of Colour · 128
XXIII. Conditions of the Increase of Colour • 134
XXIV. Explanation of the foregoing Phenomena • 139
XXV . Decrease of the Appearance of Colour • 141
• 142
XXVI. Grey Objects
XXVII. Coloured Objects 143
XXVIII. Achromatism and Hyperchromatism · 145
XXIX . Combination of Subjective and Objective Ex-
periments . 147
XXX . Transition . 150

XXXI. Catoptrical Colours • 154

XXXII. Paroptical Colours • 163

XXXIII. Epoptical Colours 177

PART III.
CHEMICAL COLOURS .
XXXIV . Chemical Contrast · 202
XXXV . White · 203
XXXVI . Black • 205
XXXVII . First Excitation of Colour · 206
XXXVIII. Augmentation of Colour · 212
XXXIX . Culmination 214
XL. Fluctuation · 217
XLI. Passage through the Whole Scale 218
XLII . Inversion · 220
XLIII. Fixation . 221
XLIV. Intermixture, Real • · 223

XLV. Intermixture, Apparent · 226

XLVI. Communication , Actual • 230
XLVII . Communication, Apparent 235
XLVIII. Extraction · 237
XLIX. Nomenclature • 242
 CONTENTS . xxxiii

PAGE
L. Minerals · 245
LI. Plants • 247
LII. Worms, Insects, Fishes 252
LIII. Birds 259
LIV. Mammalia and Human Beings 262
LV. Physical and Chemical Effects of the Transmission
of Light through Coloured Mediums • 266
LVI. Chemical Effect in Dioptrical Achromatism 270

PART IV .
GENERAL CHARACTERISTICS .

The Facility with which Colour appears · 274

The Definite Nature of Colour · 276
Combination of the Two Principles . • 277
Augmentation to Red ib.
Junction of the Two Augmented Extremes • 278
Completeness the Result of Variety in Colour 279
Harmony of the Complete State · 280
Facility with which Colour may be made to tend either to
the Plus or Minus side · 281
Evanescence of Colour · ib.
Permanence of Colour • · 282

PART V.
RELATION TO OTHER PURSUITS.
Relation to Philosophy 283
Relation to Mathematics 286
Relation to the Technical Operations ofthe Dyer • 289
Relation to Physiology and Pathology 291
Relation to Natural History • 292
Relation to General Physics 293
Relation to the Theory of Music • 298
Concluding Observations on Terminology 300

PART VI .
EFFECT OF COLOUR WITH REFERENCE TO MORAL
ASSOCIATIONS.
Yellow 306
xxxiv CONTENTS.

PAGE
· 308
Red-Yellow
Yellow- Red 309
· 310
Blue •
Red- Blue • 312
• 313
Blue-Red
ib.
Red
316
Green
ib.
Completeness and Harmony
Characteristic Combinations • 321

Yellow and Blue · 322

Yellow and Red ib.

Blue and Red ib.

Yellow-Red and Blue- Red 323
Combinations Non - Characteristic • • 324
Relation of the Combinations to Light and Dark 325
Considerations derived from the Evidence of Experience
• 326
and History
Esthetic Influence • 330
Chiaro- Scuro 331
334
Tendency to Colour
• 335
Keeping
· 337
Colouring
Colour in General Nature ib.
338
Colour of Particular Objects .
339
Characteristic Colouring
Harmonious Colouring • 341
Genuine Tone 342
False Tone ib.
Weak Colouring 343
344
The Motley
Dread of Theory ib .
Ultimate Aim 345
Grounds ib.
• 348
Pigments
Allegorical, Symbolical , Mystical Application of Colour 350
Concluding Observations • 352
 OUTLINE

OF A

THEORY OF COLOURS .

" Si vera nostra sunt aut falsa, erunt talia, licet nostra per vitam defen-
dimus. Post fata nostra pueri qui nunc ludunt nostri judices erunt."

c 2
 INTRODUCTION .

THE desire of knowledge is first stimulated in us

when remarkable phenomena attract our atten
tion. In order that this attention be continued,
it is necessary that we should feel some interest

in exercising it, and thus by degrees we become

better acquainted with the object of our curi
osity. During this process of observation we
remark at first only a vast variety which presses

indiscriminately on our view ; we are forced to

separate, to distinguish, and again to combine ;
by which means at last a certain order arises
which admits of being surveyed with more or
less satisfaction .

To accomplish this, only in a certain degree,

in any department, requires an unremitting and
close application ; and we find, for this reason ,
that men prefer substituting a general theore
tical view, or some system of explanation , for
the facts themselves, instead of taking the trou
ble to make themselves first acquainted with
cases in detail and then constructing a whole.
The attempt to describe and class the phe
nomena of colours has been only twice made :
first by Theophrastus, * and in modern times by

The treatise to which the author alludes is more generally

ascribed to Aristotle . -T.
xxxviii INTRODUCTION.

Boyle . The pretensions of the present essay

to the third place will hardly be disputed .
Our historical survey enters into further de
tails . Here we merely observe that in the last
century such a classification was not to be

thought of, because Newton had based his hypo

thesis on a phenomenon exhibited in a compli
cated and secondary state ; and to this the other
cases that forced themselves on the attention

were contrived to be referred , when they could

not be passed over in silence ; just as an astro
nomer would do, if from whim he were to place
the moon in the centre of our system ; he would
be compelled to make the earth, sun , and pla
nets revolve round the lesser body, and be forced
to disguise and gloss over the error of his first

assumption by ingenious calculations and plau

sible statements.

In our prefatory observations we assumed the

reader to be acquainted with what was known

respecting light ; here we assume the same with
regard to the eye. We observed that all nature
manifests itself by means of colours to the sense
of sight. We now assert, extraordinary as it

may in some degree appear, that the eye sees

no form , inasmuch as light, shade, and colour I

together constitute that which to our vision dis

tinguishes object from object, and the parts of

an object from each other . From these three,
light, shade , and colour, we construct the visible
 INTRODUCTION. xxxix

world, and thus, at the same time, make paint

ing possible, an art which has the power of

producing on a flat surface a much more perfect I
visible world than the actual one can be.
The eye may be said to owe its existence to
light, which calls forth , as it were , a sense that
is akin to itself ; the eye, in short, is formed
with reference to light, to be fit for the action
of light ; the light it contains corresponding with
the light without.
We are here reminded of a significant adage
in constant use with the ancient Ionian school

"Like is only known by Like ; " and again , of

the words of an old mystic writer, which may
be thus rendered , " If the eye were not sunny,
how could we perceive light ? If God's own
strength lived not in us, how could we delight
in Divine things ? " This immediate affinity
between light and the eye will be denied by
none ; to consider them as identical in sub

stance is less easy to comprehend . It will be

more intelligible to assert that a dormant

light resides in the eye, and that it may be ex

cited by the slightest cause from within or from
without. In darkness we can, by an effort of
imagination , call up the brightest images ; in
dreams objects appear to us as in broad day
light ; awake , the slightest external action of

light is perceptible, and if the organ suffers an

actual shock, light and colours spring forth.
xl INTRODUCTION.

Here, however, those who are wont to proceed

according to a certain method, may perhaps
observe that as yet we have not decidedly ex

plained what colour is. This question, like the

definition of light and the eye, we would for the
present evade, and would appeal to our inquiry
itself, where we have circumstantially shown
how colour is produced . We have only there
fore to repeat that colour is a law of nature in
relation with the sense of sight. We must as

sume, too, that every one has this sense, that

every one knows the operation of nature on it,
for to a blind man it would be impossible to
speak of colours.

That we may not, however, appear too anxious

to shun such an explanation , we would re- state
what has been said as follows : colour is an

elementary phenomenon in nature adapted to

the sense of vision ; a phenomenon which, like
all others, exhibits itself by separation and con
trast, by commixture and union , by augmenta
tion and neutralization, by communication and
dissolution under these general terms its

nature may be best comprehended .

We do not press this mode of stating the sub
ject on any one. Those who, like ourselves,
find it convenient, will readily adopt it ; but we
have no desire to enter the lists hereafter in
its defence . From time immemorial it has been
dangerous to treat of colour ; so much so, that
 INTRODUCTION . xli

one of our predecessors ventured on a certain

occasion to say, "The ox becomes furious

if a red cloth is shown to him ; but the philo-

sopher, who speaks of colour only in a general
way, begins to rave."
Nevertheless, if we are to proceed to give
some account of our work, to which we have

appealed, we must begin by explaining how

we have classed the different conditions under
which colour is produced . We found three

modes in which it appears ; three classes of

colours, or rather three exhibitions of them
all . The distinctions of these classes are easily
expressed .
Thus, in the first instance, we considered co-

lours, as far as they may be said to belong to

the eye itself, and to depend on an action and
re-action of the organ ; next, they attracted our
attention as perceived in , or by means of, colour-
less mediums ; and lastly, where we could con-
sider them as belonging to particular substances.
We have denominated the first, physiological,

the second, physical, the third , chemical colours.

The first are fleeting and not to be arrested ;
the next are passing, but still for a while en-
during ; the last may be made permanent for
any length of time.

Having separated these classes and kept them

as distinct as possible, with a view to a clear,
didactic exposition, we have been enabled at
xlii INTRODUCTION .

the same time to exhibit them in an unbroken

series, to connect the fleeting with the somewhat

more enduring, and these again with the per-

manent hues ; and thus, after having carefully
attended to a distinct classification in the first

instance, to do away with it again when a larger

view was desirable.
In a fourth division of our work we have

therefore treated generally what was previously

detailed under various particular conditions ,

and have thus , in fact, given a sketch for a

future theory of colours . We will here only an-
ticipate our statements so far as to observe, that

light and darkness, brightness and obscurity, or

if a more general expression is preferred, light
and its absence , are necessary to the production
of colour. Next to the light, a colour appears

which we call yellow ; another appears next to

the darkness , which we name blue. When

these, in their purest state, are so mixed that

they are exactly equal, they produce a third
colour called green . Each of the two first-named
colours can however of itself produce a new tint
by being condensed or darkened . They thus

acquire a reddish appearance which can be in-

creased to so great a degree that the original
blue or yellow is hardly to be recognised in it :
but the intensest and purest red , especially in
physical cases, is produced when the two ex-
tremes of the yellow-red and blue- red are
 INTRODUCTION. xliii

united. This is the actual state of the appear

ance and generation of colours . But we can

also assume an existing red in addition to the
definite existing blue and yellow, and we can pro

duce contrariwise , by mixing, what we directly

produced by augmentation or deepening . With

these three or six colours , which may be con

veniently included in a circle , the elementary

doctrine of colours is alone concerned . All

other modifications , which may be extended to

infinity, have reference more to the application ,
have reference to the technical operations of the
painter and dyer, and the various purposes of
artificial life . To point out another general

quality, we may observe that colours throughout

are to be considered as half-lights , as half

shadows, on which account if they are so mixed

as reciprocally to destroy their specific hues, a "
shadowy tint, a grey, is produced .
"
In the fifth division of our inquiry we had
proposed to point out the relations in which we
should wish our doctrine of colours to stand

to other pursuits . Important as this part of our

work is, it is perhaps on this very account not
so successful as we could wish. Yet when we
1
reflect that strictly speaking these relations
cannot be described before they exist, we may
console ourselves if we have in some degree
failed in endeavouring for the first time to
define them . For undoubtedly we should first
xliv INTRODUCTION .

Iwait to see how those whom we have endea-

voured to serve, to whom we have intended to
make an agreeable and useful offering, how such
persons, we say, will accept the result of our

utmost exertion : whether they will adopt it,

whether they will make use of it and follow it
up, or whether they will repel, reject, and suffer
it to remain unassisted and neglected .
Meanwhile, we venture to express what we
believe and hope. From the philosopher we
believe we merit thanks for having traced the
phenomena of colours to their first sources, to
the circumstances under which they simply
appear and are, and beyond which no further

explanation respecting them is possible. It will ,

besides, be gratifying to him that we have ar-
ranged the appearances described in a form that

admits of being easily surveyed , even should he

not altogether approve of the arrangement itself.

The medical practitioner, especially him

whose study it is to watch over the organ of
sight, to preserve it, to assist its defects and
to cure its disorders , we reckon to make espe-

cially our friend . In the chapter on the phy-

siological colours, in the Appendix relating to
those that are more strictly pathological, he will
find himself quite in his own province . We are
not without hopes of seeing the physiological
phenomena, a hitherto neglected , and , we may
add, most important branch of the theory of
 INTRODUCTION. xlv

colours ,―completely investigated through the

exertions of those individuals who in our own

times are treating this department with success.

The investigator of nature should receive us
cordially , since we enable him to exhibit the
doctrine of colours in the series of other ele

mentary phenomena, and at the same time

enable him to make use of a corresponding no
menclature, nay, almost the same words and
designations as under the other rubrics . It is

true we give him rather more trouble as a

teacher, for the chapter of colours is not now to
be dismissed as heretofore with a few paragraphs
and experiments ; nor will the scholar submit
to be so scantily entertained as he has hitherto

been, without murmuring. On the other hand ,

an advantage will afterwards arise out of this :
for if the Newtonian doctrine was easily learnt,
insurmountable difficulties presented themselvse
in its application . Our theory is perhaps more
difficult to comprehend , but once known, all is
accomplished, for it carries its application along
with it.

The chemist who looks upon colours as indi

cations by which he may detect the more secret
properties of material things, has hitherto found
much inconvenience in the denomination and

description of colours ; nay, some have been in

duced after closer and nicer examination to look
upon colour as an uncertain and fallacious cri
xlvi INTRODUCTION.

terion in chemical operations. Yet we hope by

means of our arrangement and the nomenclature
before alluded to, to bring colour again into
credit, and to awaken the conviction that a pro

gressive, augmenting , mutable quality, a quality

which admits of alteration even to inversion , is

not fallacious , but rather calculated to bring to

light the most delicate operations of nature .
In looking a little further round us, we are not
without fears that we may fail to satisfy another
class of scientific men . By an extraordinary com
bination of circumstances the theory of colours
has been drawn into the province and before
the tribunal of the mathematician , a tribunal to
which it cannot be said to be amenable . This
was owing to its affinity with the other laws of
vision which the mathematician was legitimately
called upon to treat . It was owing, again, to
another circumstance : a great mathematician
had investigated the theory of colours, and
having been mistaken in his observations as an
experimentalist, he employed the whole force of

his talent to give consistency to this mistake.

Were both these circumstances considered , all

misunderstanding would presently be removed ,

and the mathematician would willingly co
operate with us, especially in the physical de
partment of the theory.

To the practical man, to the dyer, on the

other hand, our labour must be altogether ac
 INTRODUCTION. xlvii

ceptable ; for it was precisely those who re

flected on the facts resulting from the opera
tions of dyeing who were the least satisfied with
the old theory : they were the first who per
ceived the insufficiency of the Newtonian doc
trine. The conclusions of men are very different

according to the mode in which they approach

a science or branch of knowledge ; from which
side, through which door they enter. The

literally practical man , the manufacturer, whose

attention is constantly and forcibly called to the
facts which occur under his eye, who experiences
benefit or detriment from the application of his
convictions , to whom loss of time and money is
not indifferent , who is desirous of advancing ,

who aims at equalling or surpassing what others

have accomplished , -such a person feels the
unsoundness and erroneousness of a theory
much sooner than the man of letters, in whose

eyes words consecrated by authority are at last

equivalent to solid coin ; than the mathematician ,
whose formula always remains infallible, even
although the foundation on which it is con
structed may not square with it. Again, to

carry on the figure before employed, in entering

this theory from the side of painting, from the
side of æsthetic* colouring generally , we shall be

Esthetic-belonging to taste as mere internal sense, from

aioðávoμai, to feel ; the word was first used by Wolf.-T.
xlviii INTRODUCTION.

found to have accomplished a most thankworthy

office for the artist . In the sixth part we have
endeavoured to define the effects of colour as ad-

dressed at once to the eye and mind , with a view

to making them more available for the purposes
of art. Although much in this portion, and in-
deed throughout, has been suffered to remain as
a sketch, it should be remembered that all

theory can in strictness only point out leading

principles, under the guidance of which , prac-
tice may proceed with vigour and be enabled to

attain legitimate results .

 PART I.

PHYSIOLOGICAL COLOURS .

1.

We naturally place these colours first, because

they belong altogether, or in a great degree, to
the subject * —to the eye itself. They are the
foundation of the whole doctrine, and open to

our view the chromatic harmony on which so

much difference of opinion has existed . They
have been hitherto looked upon as extrinsic and
!
casual, as illusion and infirmity : their appear-
ances have been known from ancient date ; but,
as they were too evanescent to be arrested , they
were banished into the region of phantoms , and
under this idea have been very variously described .

2.

Thus they are called colores adventicii by Boyle ;

imaginarii and phantastici by Rizetti ; by Buffon ,
1
couleurs accidentelles ; by Scherfer, scheinfarben

(apparent colours) ; ocular illusions and deceptions

The German distinction between subject and object is so

generally understood and adopted, that it is hardly necessary
to explain that the subject is the individual, in this case the
beholder ; the object, all that is without him.-I.
B
2 PHYSIOLOGICAL COLOURS .

of sight by many ; by Hamberger, vitia fugitiva ;

by Darwin, ocular spectra .

3.

We have called them physiological because

they belong to the eye in a healthy state ; be-
cause we consider them as the necessary con-

ditions of vision ; the lively alternating action of

which, with reference to external objects and a
principle within it, is thus plainly indicated .

4.

To these we subjoin the pathological colours,

which, like all deviations from a constant law,

afford a more complete insight into the nature of

the physiological colours .

EFFECTS OF LIGHT AND DARKNESS ON THE EYE.

5.

The retina, after being acted upon by light or

darkness, is found to be in two different states ,
which are entirely opposed to each other.

6.

If we keep the eyes open in a totally dark

place, a certain sense of privation is experienced .
The organ is abandoned to itself ; it retires into

itself. That stimulating and grateful contact is

wanting by means of which it is connected with

the external world, and becomes part of a whole .

 EFFECTS OF LIGHT AND DARKNESS . 3

7.

If we look on a white, strongly illumined sur

face, the eye is dazzled , and for a time is in

capable of distinguishing objects moderately

lighted .

8.

The whole of the retina is acted on in each of

these extreme states , and thus we can only ex

perience one of these effects at a time . In the
one case (6) we found the organ in the utmost
relaxation and susceptibility ; in the other (7)
in an overstrained state, and scarcely susceptible
at all .
9.

If we pass suddenly from the one state to the

other, even without supposing these to be the
extremes, but only, perhaps , a change from
bright to dusky, the difference is remarkable ,
and we find that the effects last for some time.

10.

In passing from bright daylight to a dusky

place we distinguish nothing at first : by degrees
the eye recovers its susceptibility ; strong eyes
sooner than weak ones ; the former in a minute,
while the latter may require seven or eight
minutes.
11 .

The fact that the eye is not susceptible to faint

B 2
4 EFFECTS OF LIGHT AND DARKNESS

impressions of light, if we pass from light to

comparative darkness, has led to curious mis-
takes in scientific observations. Thus an ob-

server, whose eyes required some time to recover

their tone, was long under the impression that
rotten wood did not emit light at noon- day, even
in a dark room. The fact was, he did not see the
faint light, because he was in the habit of pass-
ing from bright sunshine to the dark room , and
only subsequently remained so long there that
the eye had time to recover itself.
The same may have happened to Doctor
Wall , who, in the daytime, even in a dark room,
could hardly perceive the electric light of amber.
Our not seeing the stars by day, as well as the
improved appearance of pictures seen through a
double tube, is also to be attributed to the same
cause .

12.

If we pass from a totally dark place to one

illumined by the sun, we are dazzled . In coming
from a lesser degree of darkness to light that is
not dazzling, we perceive all objects clearer and
better hence eyes that have been in a state of
repose are in all cases better able to perceive
moderately distinct appearances .
Prisoners who have been long confined in
darkness acquire so great a susceptibility of the
retina, that even in the dark (probably a dark-
 ON THE EYE. 5

ness very slightly illumined ) they can still dis

tinguish objects .

13.

In the act which we call seeing, the retina is

at one and the same time in different and even

opposite states . The greatest brightness, short

of dazzling, acts near the greatest darkness . In
this state we at once perceive all the intermediate
gradations of chiaro-scuro, and all the varieties of
hues .

14.

We will proceed in due order to consider and

examine these elements of the visible world , as
well as the relation in which the organ itself
stands to them, and for this purpose we take the

simplest objects.

II.

EFFECTS OF BLACK AND WHITE OBJECTS ON THE EYE.

15.

In the same manner as the retina generally is

affected by brightness and darkness , so it is
affected by single bright or dark objects . If
light and dark produce different results on the
whole retina, so black and white objects seen at
6 EFFECTS OF BLACK AND

the same time produce the same states together

which light and dark occasioned in succession .

16.

A dark object appears smaller than a bright

one of the same size. Let a white disk be placed
on a black ground , and a black disk on a white
ground, both being exactly similar in size ; let
them be seen together at some distance, and we
shall pronounce the last to be about a fifth part
smaller than the other. If the black circle be

made larger by so much, they will appear equal . *

17.

Thus Tycho de Brahe remarked that the moon

in conjunction (the darker state) appears about
a fifth part smaller than when in opposition (the
bright full state) . The first crescent appears to
belong to a larger disk than the remaining dark

portion, which can sometimes be distinguished

at the period of the new moon . Black dresses

make people appear smaller than light ones .

Lights seen behind an edge make an apparent
notch in it. A ruler, behind which the flame of
a light just appears , seems to us indented . The

rising or setting sun appears to make a notch in

the horizon .

18 .

Black, as the equivalent of darkness , leaves

* Plate i. fig. 1.
 Fu 1.

Fig 2. Fig 3

Red

E Purple Orang

Blu Yellow

Green

미
Fig t
 WHITE OBJECTS ON THE EYE.

the organ in a state of repose ; white, as the re

presentative of light, excites it. We may, per
haps , conclude from the above experiment ( 16)
that the unexcited retina , if left to itself, is drawn
together, and occupies a less space than in its
active state, produced by the excitement of light.
Hence Kepler says very beautifully : " Certum
est vel in retinâ caussâ picturæ, vel in spiritibus
caussâ impressionis , exsistere dilatationem luci

dorum . "-Paralip . in Vitellionem, p . 220. Scher

fer expresses a similar conjecture . - Note A.

19 .

However this may be, both impressions

derived from such objects remain in the organ
itself, and last for some time, even when the
external cause is removed . In ordinary ex

perience we scarcely notice this, for objects

are seldom presented to us which are very
strongly relieved from each other, and we avoid
looking at those appearances that dazzle the
sight. In glancing from one object to another ;
the succession of images appears to us distinct ;
we are not aware that some portion of the im
pression derived from the object first contem
plated passes to that which is next looked at.

20.

If in the morning, on waking, when the eye

is very susceptible, we look intently at the bars
8 EFFECTS OF BLACK AND

of a window relieved against the dawning sky,

and then shut our eyes or look towards a totally

dark place, we shall see a dark cross on a light
ground before us for some time.

21 .

Every image occupies a certain space on the

retina, and of course a greater or less space in

proportion as the object is seen near or at a

distance . If we shut the eyes immediately

after looking at the sun we shall be surprised to

find how small the image it leaves appears .

22.

If, on the other hand, we turn the open eye

towards the side of a room, and consider the

visionary image in relation to other objects, we

shall always see it larger in proportion to the
distance of the surface on which it is thrown.

This is easily explained by the laws of perspec

tive, according to which a small object near
covers a great one at a distance .

23.

The duration of these visionary impressions

varies with the powers or structure of the eye

in different individuals, just as the time neces
sary for the recovery of the tone of the retina

varies in passing from brightness to darkness

(10) : it can be measured by minutes and se
 WHITE OBJECTS ON THE EYE. 9

conds, indeed much more exactly than it could

formerly have been by causing a lighted lin-
stock to revolve rapidly, so as to appear a cir-
cle.-Note B.

24.

But the force with which an impinging light

impresses the eye is especially worthy of atten-

tion . The image of the sun lasts longest ; other

objects, of various degrees of brightness , leave
the traces of their appearance on the eye for a
proportionate time.

25.

These images disappear by degrees , and

diminish at once in distinctness and in size .

26 .

They are reduced from the contour inwards ,

and the impression on some persons has been
that in square images the angles become gra-
dually blunted till at last a diminished round
image floats before the eye.

27.

Such an image, when its impression is no

more observable, can, immediately after, be
again revived on the retina by opening and
shutting the eye, thus alternately exciting and
resting it.
10 EFFECTS OF BLACK AND

28 .

Images may remain on the retina in morbid

affections of the eye for fourteen, seventeen

minutes , or even longer. This indicates extreme
weakness of the organ , its inability to recover

itself ; while visions of persons or things which

are the objects of love or aversion indicate the
connexion between sense and thought.

29.

If, while the image of the window- bars before

mentioned lasts, we look upon a light grey sur

face, the cross will then appear light and the

panes dark. In the first case ( 20) the image
was like the original picture, so that the vision
ary impression also could continue unchanged ;
but in the present instance our attention is

excited by a contrary effect being produced .

Various examples have been given by observers
of nature .

30.

The scientific men who made observations in

the Cordilleras saw a bright appearance round

the shadows of their heads on some clouds .

This example is a case in point ; for, while they

fixed their eyes on the dark shadow, and at the
same time moved from the spot, the compensa

tory light image appeared to float round the

 WHITE OBJECTS ON THE EYE. 11

real dark one. If we look at a black disk on a

light grey surface, we shall presently, by

changing the direction of the eyes in the slight-
est degree , see a bright halo floating round the
dark circle .

A similar circumstance happened to myself :

for while, as I sat in the open air, I was talking
to a man who stood at a little distance from me

relieved on a grey sky, it appeared to me , as I

slightly altered the direction of my eyes, after
having for some time looked fixedly at him ,
that his head was encircled with a dazzling

light.
In the same way probably might be explained
the circumstance that persons crossing dewy
meadows at sunrise see a brightness round each
*
other's heads ; the brightness in this case may
1
be also iridescent, as the phenomena of refrac-
tion come into the account.

Thus again it has been asserted that the

shadows of a balloon thrown on clouds were

bordered with bright and somewhat variegated

circles .

Beccaria made use of a paper kite in some

experiments on electricity . Round this kite

appeared a small shining cloud varying in size ;

the same brightness was even observed round

part of the string. Sometimes it disappeared ,

See the Life of Benvenuto Cellini, vol. i . p . 453. Milan edi-

tion, 1806.-T.
12 EFFECTS OF BLACK AND

and if the kite moved faster the light appeared

to float to and fro for a few moments on the
place before occupied . This appearance, which

could not be explained by those who observed

it at the time, was the image which the eye re
tained of the kite relieved as a dark mass on

a bright sky ; that image being changed into a

light mass on a comparatively dark back

ground.
In optical and especially in chromatic expe
riments, where the observer has to do with

bright lights whether colourless or coloured ,

great care should be taken that the spectrum
which the eye retains in consequence of a pre
vious observation does not mix with the suc
ceeding one, and thus affect the distinctness

and purity of the impression.

31 .

These appearances have been explained as

follows : That portion of the retina on which
the dark cross (29) was impressed is to be con
sidered in a state of repose and susceptibility.
On this portion therefore the moderately light
surface acted in a more lively manner than on

the rest of the retina , which had just been im

pressed with the light through the panes, and
which, having thus been excited by a much
stronger brightness, could only view the grey
surface as a dark .
 WHITE OBJECTS ON THE EYE. 13

32 .

This mode of explanation appears sufficient

for the cases in question , but, in the considera
tion of phenomena hereafter to be adduced , we
are forced to trace the effects to higher sources .

33.

The eye after sleep exhibits its vital elas

ticity more especially by its tendency to al
ternate its impressions, which in the simplest
form change from dark to light, and from light
to dark. The eye cannot for a moment remain
in a particular state determined by the object it
looks upon. On the contrary, it is forced to a

sort of opposition , which , in contrasting extreme

with extreme, intermediate degree with inter
mediate degree, at the same time combines these
opposite impressions , and thus ever tends to a
whole, whether the impressions are successive,
or simultaneous and confined to one image.

34.

Perhaps the peculiarly grateful sensation

which we experience in looking at the skilfully
treated chiaro- scuro of colourless pictures and
similar works of art arises chiefly from the
simultaneous impression of a whole, which by the
organ itself is sought, rather than arrived at, in

succession, and which, whatever may be the re

sult, can never be arrested .
14 GREY SURFACES AND OBJECTS .

III.

GREY SURFACES AND OBJECTS .

35.

A MODERATE light is essential to many chro

matic experiments . This can be presently ob
tained by surfaces more or less grey, and thus
we have at once to make ourselves acquainted
with this simplest kind of middle tint, with re
gard to which it is hardly necessary to observe,
that in many cases a white surface in shadow,

or in a low light, may be considered equivalent

to a grey .

36 .

Since a grey surface is intermediate between

brightness and darkness , it admits of our illus
trating a phenomenon before described ( 29) by
an easy experiment.

37.

Let a black object be held before a grey sur

face, and let the spectator, after looking stead
fastly at it, keep his eyes unmoved while it is
taken away the space it occupied appears

much lighter. Let a white object be held up in

the same manner : on taking it away the space

it occupied will appear much darker than the

 GREY SURFACES AND OBJECTS . 15

rest of the surface. Let the spectator in both

cases turn his eyes this way and that on the sur-
face, the visionary images will move in like
manner .

38 .

A grey object on a black ground appears

much brighter than the same object on a white
ground . If both comparisons are seen together
the spectator can hardly persuade himself that
the two greys are identical. We believe this

again to be a proof of the great excitability of

the retina , and of the silent resistance which
every vital principle is forced to exhibit when
any definite or immutable state is presented to
it. Thus inspiration already presupposes ex-
piration ; thus every systole its diastole. It is
the universal formula of life which manifests
itself in this as in all other cases . When dark-

ness is presented to the eye it demands bright-

ness, and vice versa : it shows its vital energy,
its fitness to receive the impression of the object,
precisely by spontaneously tending to an op-
posite state .
16 DAZZLING COLOURLESS OBJECTS .

IV.

DAZZLING COLOURLESS OBJECTS .

39.

If we look at a dazzling, altogether colourless

object, it makes a strong lasting impression , and
its after- vision is accompanied by an appearance
of colour.

40.

Let a room be made as dark as possible ; let

there be a circular opening in the window
shutter about three inches in diameter, which
may be closed or not at pleasure . The sun

being suffered to shine through this on a white

surface, let the spectator from some little dis
tance fix his eyes on the bright circle thus
admitted . The hole being then closed , let him
look towards the darkest part of the room ; a
circular image will now be seen to float before
him. The middle of this circle will appear

bright, colourless, or somewhat yellow, but the

border will at the same moment appear red .

After a time this red , increasing towards the

centre, covers the whole circle, and at last the

bright central point. No sooner , however, is

the whole circle red than the edge begins to be
blue, and the blue gradually encroaches inwards
 DAZZLING COLOURLESS OBJECTS . 17

on the red. When the whole is blue the edge

becomes dark and colourless . This darker edge
again slowly encroaches on the blue till the

whole circle appears colourless . The image

then becomes gradually fainter, and at the same
time diminishes in size. Here again we see

how the retina recovers itself by a succession of

vibrations after the powerful external impression
it received. (25, 26.)

41 .

By several repetitions similar in result , I found

the comparative duration of these appearances
in my own case to be as follows :—

I looked on the bright circle five seconds , and

then, having closed the aperture, saw the co
loured visionary circle floating before me. After
thirteen seconds it was altogether red ; twenty

nine seconds next elapsed till the whole was blue,

and forty-eight seconds till it appeared colour
less . By shutting and opening the eye I con
stantly revived the image, so that it did not
quite disappear till seven minutes had elapsed .
Future observers may find these periods
shorter or longer as their eyes may be stronger
or weaker ( 23 ) , but it would be very remarkable
if, notwithstanding such variations , a correspond
ing proportion as to relative duration should be
found to exist.
C
18 DAZZLING COLOURLESS OBJECTS .

42.

But this remarkable phenomenon no sooner

excites our attention than we observe a new
modification of it.

If we receive the impression of the bright

circle as before, and then look on a light grey
surface in a moderately lighted room, an image
again floats before us ; but in this instance a
dark one : by degrees it is encircled by a green
border that gradually spreads inwards over the
whole circle , as the red did in the former
instance. As soon as this has taken place a
dingy yellow appears, and , filling the space as
the blue did before, is finally lost in a negative
shade.
43 .

These two experiments may be combined by

placing a black and a white plane surface next
each other in a moderately lighted room, and

then looking alternately on one and the other

as long as the impression of the light circle lasts :
the spectator will then perceive at first a red
and green image alternately , and afterwards the
other changes. After a little practice the two
opposite colours may be perceived at once, by
causing the floating image to fall on the junction
of the two planes . This can be more conve
niently done if the planes are at some distance,
for the spectrum then appears larger.
 DAZZLING COLOURLESS OBJECTS . 19

44.

I happened to be in a forge towards evening

at the moment when a glowing mass of iron was
placed on the anvil ; I had fixed my eyes stead-
fastly on it, and, turning round , I looked acci-
dentally into an open coal- shed : a large red
image now floated before my eyes, and, as I
turned them from the dark opening to the light
boards of which the shed was constructed , the

image appeared half green, half red, according

as it had a lighter or darker ground behind it .
I did not at that time take notice of the sub-

sequent changes of this appearance .

4.5.

The after-vision occasioned by a total dazzling

of the retina corresponds with that of a circum-
scribed bright object. The red colour seen by
persons who are dazzled with snow belongs to
this class of phenomena, as well as the singularly
beautiful green colour which dark objects seem
to wear after looking long on white paper in the
sun . The details of such experiments may be

investigated hereafter by those whose young

eyes are capable of enduring such trials further
for the sake of science .

46 .

With these examples we may also class the

black letters which in the evening light appear
C 2
20 COLOURED OBJECTS .

red. Perhaps we might insert under the same

category the story that drops of blood appeared
on the table at which Henry IV. of France had
seated himself with the Duc de Guise to play at
dice .

V.

COLOURED OBJECTS.

47.

WE have hitherto seen the physiological

colours displayed in the after- vision of colour

less bright objects , and also in the after-vision
of general colourless brightness ; we shall now
find analogous appearances if a given colour be
presented to the eye : in considering this , all
that has been hitherto detailed must be present
to our recollection .

48.

The impression of coloured objects remains

in the eye like that of colourless ones, but in
this case the energy of the retina, stimulated as
it is to produce the opposite colour, will be more
apparent.
49.

Let a small piece of bright- coloured paper or

silk stuff be held before a moderately lighted
white surface ; let the observer look steadfastly
 1

COLOURED OBJECTS. 21

on the small coloured object, and let it be taken

away after a time while his eyes remain un
moved ; the spectrum of another colour will then

be visible on the white plane . The coloured

paper may be also left in its place while the eye
is directed to another part of the white plane ;
the same spectrum will be visible there too , for

it arises from an image which now belongs to

the eye.

50.

In order at once to see what colour will be

evoked by this contrast, the chromatic circle *

may be referred to . The colours are here ar
ranged in a general way according to the
natural order, and the arrangement will be

found to be directly applicable in the present

case ; for the colours diametrically opposed to
each other in this diagram are those which reci
procally evoke each other in the eye. Thus,
yellow demands purple ; orange, blue ; red,
green ; and vice versa : thus again all interme

diate gradations reciprocally evoke each other ;

the simpler colour demanding the compound ,
and vice versa .- Note C.

51 .

The cases here under consideration occur

oftener than we are aware in ordinary life ; in

* Plate 1 , fig. 3.
22 COLOURED OBJECTS .

deed, an attentive observer sees these appear

ances everywhere, while , on the other hand , the

uninstructed , like our predecessors , consider

them as temporary visual defects, sometimes
even as symptoms of disorders in the eye, thus
exciting serious apprehensions . A few remark
able instances may here be inserted .

52.

I had entered an inn towards evening, and ,

as a well-favoured girl, with a brilliantly fair
complexion, black hair, and a scarlet bodice ,
came into the room , I looked attentively at her
as she stood before me at some distance in half
shadow. As she presently afterwards turned
away, I saw on the white wall, which was now

before me, a black face surrounded with a bright

light, while the dress of the perfectly distinct
figure appeared of a beautiful sea-green .
53.

Among the materials for optical experiments,

there are portraits with colours and shadows
exactly opposite to the appearance of nature .
The spectator, after having looked at one of
these for a time, will see the visionary figure

tolerably true to nature . This is conformable

to the same principles, and consistent with ex
perience, for, in the former instance , a negress
with a white head-dress would have given me a
white face surrounded with black. In the case
 COLOURED OBJECTS . 23

of the painted figures, however, which are com

monly small, the parts are not distinguishable
by every one in the after- image.

54 .

A phenomenon which has before excited

attention among the observers of nature is to
be attributed , I am persuaded , to the same
cause .

It has been stated that certain flowers , towards

evening in summer, coruscate, become phos

phorescent, or emit a momentary light. Some
persons have described their observation of

this minutely . I had often endeavoured to

witness it myself, and had even resorted to
artificial contrivances to produce it.
On the 19th of June, 1799, late in the evening ,

when the twilight was deepening into a clear

night, as I was walking up and down the garden
with a friend , we very distinctly observed a
flame-like appearance near the oriental poppy,
the flowers of which are remarkable for their

powerful red colour. We approached the place

and looked attentively at the flowers, but could
perceive nothing further, till at last, by passing
and repassing repeatedly, while we looked side
ways on them, we succeeded in renewing the
appearance as often as we pleased . It proved
to be a physiological phenomenon, such as
others we have described , and the apparent
24 COLOURED OBJECTS .

coruscation was nothing but the spectrum of the

flower in the compensatory blue-green colour .
In looking directly at a flower the image is
not produced , but it appears immediately as the
direction of the eye is altered . Again , by look
ing sideways on the object, a double image is
seen for a moment, for the spectrum then
appears near and on the real object .
The twilight accounts for the eye being in a
perfect state of repose, and thus very susceptible,
and the colour of the poppy is sufficiently

powerful in the summer twilight of the longest

days to act with full effect and produce a com
pensatory image. I have no doubt these ap
pearances might be reduced to experiment, and
the same effect produced by pieces of coloured
paper. Those who wish to take the most
effectual means for observing the appearance in

nature-suppose in a garden- should fix the eyes

on the bright flowers selected for the purpose,
and, immediately after, look on the gravel path.
This will be seen studded with spots of the
opposite colour. The experiment is practicable
on a cloudy day, and even in the brightest sun
shine, for the sun-light, by enhancing the bril
liancy of the flower, renders it fit to produce the
compensatory colour sufficiently distinct to be

perceptible even in a bright light . Thus, peonies

produce beautiful green , marigolds vivid blue
spectra .
 COLOURED OBJECTS . 25

55.

As the opposite colour is produced by a con

stant law in experiments with coloured objects
on portions of the retina, so the same effect
takes place when the whole retina is impressed
with a single colour. We may convince our
selves of this by means of coloured glasses . If
we look long through a blue pane of glass ,

everything will afterwards appear in sunshine to

the naked eye, even if the sky is grey and the
scene colourless . In like manner, in taking off
green spectacles , we see all objects in a red
light . Every decided colour does a certain vio
lence to the eye, and forces the organ to
opposition.

56 .

We have hitherto seen the opposite colours

producing each other successively on the retina :

it now remains to show by experiment that the

same effects can exist simultaneously . If a
coloured object impinges on one part of the
retina , the remaining portion at the same mo
ment has a tendency to produce the compensa

tory colour. To pursue a former experiment, if

we look on a yellow piece of paper placed on a
white surface, the remaining part of the organ

has already a tendency to produce a purple hue

on the colourless surface : in this case the small

portion of yellow is not powerful enough to pro

26 COLOURED OBJECTS .

duce this appearance distinctly, but, if a white

paper is placed on a yellow wall, we shall see
the white tinged with a purple hue .

57.

Although this experiment may be made with

any colours , yet red and green are particularly

recommended for it, because these colours seem
powerfully to evoke each other. Numerous in

stances occur in daily experience . If a green

paper is seen through striped or flowered muslin ,

the stripes or flowers will appear reddish . A

grey building seen through green pallisades

appears in like manner reddish. A modification

of this tint in the agitated sea is also a com

pensatory colour : the light side of the waves
appears green in its own colour, and the sha

dowed side is tinged with the opposite hue . The

different direction of the waves with reference

to the eye produces the same effect . Objects

seen through an opening in a red or green cur
tain appear to wear the opposite hue. These
appearances will present themselves to the atten
tive observer on all occasions, even to an un

pleasant degree.
58.

Having made ourselves acquainted with the

simultaneous exhibition of these effects in direct
cases , we shall find that we can also observe

them by indirect means. If we place a piece of

 COLOURED OBJECTS . 27

paper of a bright orange colour on the white

surface, we shall, after looking intently at it,

scarcely perceive the compensatory colour on
the rest of the surface : but when we take the

orange paper away, and when the blue spectrum

appears in its place, immediately as this spec
trum becomes fully apparent, the rest of the
surface will be overspread , as if by a flash, with
a reddish-yellow light, thus exhibiting to the
spectator in a lively manner the productive
energy of the organ , in constant conformity with
the same law.

59.

As the compensatory colours easily appear,

where they do not exist in nature, near and
after the original opposite ones, so they are ren
dered more intense where they happen to mix
with a similar real hue . In a court which was

paved with grey limestone flags, between which

grass had grown, the grass appeared of an ex

tremely beautiful green when the evening clouds

threw a scarcely perceptible reddish light on
the pavement. In an opposite case we find ,
in walking through meadows, where we see
scarcely anything but green, the stems of trees
and the roads often gleam with a reddish hue.
This tone is not uncommon in the works of
landscape painters, especially those who prac
tice in water- colours : they probably see it in
28 COLOURED OBJECTS .

nature , and thus, unconsciously imitating it,

their colouring is criticised as unnatural .

60.

These phenomena are of the greatest import

ance, since they direct our attention to the laws
of vision , and are a necessary preparation for
future observations on colours. They show that
the eye especially demands completeness , and
seeks to eke out the colorific circle in itself.

The purple or violet colour suggested by yellow

contains red and blue ; orange, which responds

to blue, is composed of yellow and red ; green ,

uniting blue and yellow, demands red ; and so
through all gradations of the most complicated
combinations . That we are compelled in this
case to assume three leading colours has been
already remarked by other observers.

61.

When in this completeness the elements of

which it is composed are still appreciable by

the eye, the result is justly called harmony.

We shall subsequently endeavour to show how
the theory of the harmony of colours may be
deduced from these phenomena, and how, sim

ply through these qualities , colours may be ca

pable of being applied to æsthetic purposes .
This will be shown when we have gone through
the whole circle of our observations , returning

to the point from which we started .

 COLOURED SHADOWS. 29

VI .

COLOURED SHADOWS .

62.

BEFORE, however, we proceed further, we have

yet to observe some very remarkable cases of
the vivacity with which the suggested colours
appear in the neighbourhood of others : we al
lude to coloured shadows . To arrive at these
we first turn our attention to shadows that are
colourless or negative .

63.

A shadow cast by the sun , in its full bright

ness , on a white surface, gives us no impression
of colour ; it appears black, or, if a contrary
light ( here assumed to differ only in degree) can
act upon it, it is only weaker, half-lighted, grey.

64.

Two conditions are necessary for the existence

of coloured shadows : first, that the principal
light tinge the white surface with some hue ;
secondly, that a contrary light illumine to a
certain extent the cast shadow.

65.

Let a short, lighted candle be placed at twi

light on a sheet of white paper . Between it
and the declining daylight let a pencil be placed
30 COLOURED SHADOWS.

upright, so that its shadow thrown by the candle

may be lighted , but not overcome, by the weak
daylight the shadow will appear of the most
beautiful blue.

66.

That this shadow is blue is immediately evi

dent ; but we can only persuade ourselves by
some attention that the white paper acts as a
reddish yellow, by means of which the comple
mental blue is excited in the eye . - Note D.

67.

In all coloured shadows, therefore, we must

presuppose a colour excited or suggested by the
hue of the surface on which the shadow is

thrown . This may be easily found to be the

case by attentive consideration , but we may
convince ourselves at once by the following ex

periment.

68.

Place two candles at night opposite each

other on a white surface ; hold a thin rod be

tween them upright, so that two shadows be
cast by it ; take a coloured glass and hold it be
fore one of the lights, so that the white paper
appear coloured ; at the same moment the sha
dow cast by the coloured light and slightly illu
mined by the colourless one will exhibit the
complemental hue.
 COLOURED SHADOWS . 31

69.

An important consideration suggests itself

here, to which we shall frequently have occasion
to return . Colour itself is a degree of darkness
( xpó ) ; hence Kircher is perfectly right in
calling it lumen opacatum . As it is allied to
shadow, so it combines readily with it ; it ap
pears to us readily in and by means of shadow
the moment a suggesting cause presents itself.
We could not refrain from adverting at once to

a fact which we propose to trace and develop

hereafter.- Note E.

70.

Select the moment in twilight when the light

of the sky is still powerful enough to cast a sha
dow which cannot be entirely effaced by the
light of a candle . The candle may be so placed
that a double shadow shall be visible, one from

the candle towards the daylight, and another

from the daylight towards the candle . If the
former is blue the latter will appear orange

yellow this orange-yellow is in fact, however,

only the yellow- red light of the candle diffused
over the whole paper, and which becomes visible
in shadow.

71 .

This is best exemplified by the former expe

riment with two candles and coloured glasses .
32 COLOURED SHADOWS .

The surprising readiness with which shadow as

sumes a colour will again invite our attention
in the further consideration of reflections and
elsewhere .

72 .

Thus the phenomena of coloured shadows

may be traced to their cause without difficulty.
Henceforth let any one who sees an instance of
the kind observe only with what hue the light
surface on which they are thrown is tinged .

Nay, the colour of the shadow may be considered

as a chromatoscope of the illumined surface, for
the spectator may always assume the colour of
the light to be the opposite of that of the sha
dow, and by an attentive examination may as
certain this to be the fact in every instance.

73 .

These appearances have been a source of

great perplexity to former observers : for, as

they were remarked chiefly in the open air,

where they commonly appeared blue, they were
attributed to à certain inherent blue or blue co

louring quality in the air. The inquirer can ,

however, convince himself, by the experiment
with the candle in a room, that no kind of blue
light or reflection is necessary to produce the
effect in question . The experiment may be

made on a cloudy day with white curtains drawn

 COLOURED SHADOWS . 33

before the light, and in a room where no trace

of blue exists, and the blue shadow will be only

so much the more beautiful.

74.

De Saussure, in the description of his ascent

of Mont Blanc, says, " A second remark , which
may not be uninteresting, relates to the colour
of the shadows . These, notwithstanding the
most attentive observation , we never found dark

blue, although this had been frequently the case

in the plain . On the contrary , in fifty - nine in-
stances we saw them once yellowish, six times
pale bluish, eighteen times colourless or black,

and thirty-four times pale violet. Some natural

philosophers suppose that these colours arise

from accidental vapours diffused in the air, which

communicate their own hues to the shadows ;
not that the colours of the shadows are occa-

sioned by the reflection of any given sky colour

or interposition of any given air colour : the
above observations seem to favour this opinion ."
The instances given by De Saussure may be
now explained and classed with analogous ex-
amples without difficulty.
At a great elevation the sky was generally
free from vapours , the sun shone in full force on
the snow, so that it appeared perfectly white to
the eye : in this case they saw the shadows
quite colourless . Ifthe air was charged with a
Ꭰ
34 COLOURED SHADOWS.

certain degree of vapour, in consequence of

which the light snow would assume a yellowish
tone, the shadows were violet- coloured , and this

effect, it appears, occurred oftenest . They saw

also bluish shadows, but this happened less fre
quently ; and that the blue and violet were pale
was owing to the surrounding brightness , by
which the strength of the shadows was miti
gated . Once only they saw the shadow yellow
ish in this case, as we have already seen (70) ,

the shadow is cast by a colourless light, and

slightly illumined by a coloured one.

75.

In travelling over the Harz in winter, I hap

pened to descend from the Brocken towards

evening ; the wide slopes extending above and

below me, the heath, every insulated tree and

projecting rock, and all masses of both, were

covered with snow or hoar- frost . The sun was

sinking towards the Oder ponds. * During the

day, owing to the yellowish hue of the snow,
shadows tending to violet had already been ob
servable ; these might now be pronounced to be
decidedly blue, as the illumined parts exhibited
a yellow deepening to orange .
But as the sun at last was about to set , and
its rays, greatly mitigated by the thicker va

* Reservoirs in which water is collected from various small

streams, to work the mines .-T.
 COLOURED SHADOWS . 35

1
pours, began to diffuse a most beautiful red
colour over the whole scene around me, the

shadow colour changed to a green, in lightness

to be compared to a sea-green, in beauty to the

green ofthe emerald . The appearance became
more and more vivid : one might have imagined
oneself in a fairy world, for every object had
clothed itself in the two vivid and so beautifully

harmonising colours, till at last, as the sun went

down, the magnificent spectacle was lost in a
grey twilight, and by degrees in a clear moon-
and-starlight night.

76 .

One of the most beautiful instances of co-

loured shadows may be observed during the

full moon . The candle-light and moon -light

may be contrived to be exactly equal in

force ; both shadows may be exhibited with
equal strength and clearness, so that both co-
lours balance each other perfectly. A white
surface being placed opposite the full moon,
and the candle being placed a little on one side
at a due distance, an opaque body is held be-
fore the white plane. A double shadow will

then be seen that cast by the moon and illu-

mined by the candle-light will be a powerful
red-yellow ; and contrariwise, that cast by the
candle and illumined by the moon will appear
of the most beautiful blue. The shadow, com-
posed of the union of the two shadows, where
D2
36 COLOURED SHADOWS.

they cross each other, is black . The yellow

shadow (74) cannot perhaps be exhibited in a

more striking manner. The immediate vicinity

of the blue and the interposing black shadow

make the appearance the more agreeable . It
will even be found, if the eye dwells long on
these colours, that they mutually evoke and
enhance each other, the increasing red in the
one still producing its contrast, viz . a kind of
sea-green .

77.

We are here led to remark that in this , and

in all cases , a moment or two may perhaps be
necessary to produce the complemental colour.
The retina must be first thoroughly impressed
with the demanding hue before the responding
one can be distinctly observable .

78.

When divers are under water, and the sun-

light shines into the diving-bell , everything is
seen in a red light (the cause of which will be
explained hereafter) , while the shadows appear
green. The very same phenomenon which I
observed on a high mountain (75) is presented
to others in the depths of the sea, and thus Na-
ture throughout is in harmony with herself.

79.

Some observations and experiments which

equally illustrate what has been stated with re-
 COLOURED SHADOWS . 37

gard to coloured objects and coloured shadows

may be here added . Let a white paper blind
be fastened inside the window on a winter even

ing ; in this blind let there be an opening,

through which the snow of some neighbouring
roof can be seen . Towards dusk let a candle be

brought into the room ; the snow seen through

the opening will then appear perfectly blue, be
cause the paper is tinged with warm yellow by
the candle- light. The snow seen through the
aperture is here equivalent to a shadow illu

mined by a contrary light (76) , and may also

represent a grey disk on a coloured surface (56 ) .

80.

Another very interesting experiment may

conclude these examples . If we take a piece
of green glass of some thickness , and hold it so

that the window bars be reflected in it, they

will appear double owing to the thickness of the

glass . The image which is reflected from the

under surface of the glass will be green ; the

image which is reflected from the upper surface,

and which should be colourless , will appear red.

The experiment may be very satisfactorily

made by pouring water into a vessel , the inner
surface of which can act as a mirror ; for both
reflections may first be seen colourless while the

water is pure, and then by tinging it, they will

exhibit two opposite hues .
38 FAINT LIGHTS .

VII.

FAINT LIGHTS .

81 .

LIGHT, in its full force, appears purely white,

and it gives this impression also in its highest
degree of dazzling splendour . Light, which is
not so powerful, can also, under various condi
tions , remain colourless . Several naturalists
and mathematicians have endeavoured to mea
sure its degrees-Lambert , Bouguer, Rumfort.

82.

Yet an appearance of colour presently mani

fests itself in fainter lights, for in their relation
to absolute light they resemble the coloured
spectra of dazzling objects (39) .

83.

A light of any kind becomes weaker, either

when its own force, from whatever cause, is di

minished , or when the eye is so circumstanced

or placed , that it cannot be sufficiently im
pressed by the action of the light. Those ap
pearances which may be called objective, come
under the head of physical colours . We will
only advert here to the transition from white to
red heat in glowing iron . We may also observe
 FAINT LIGHTS . 39

that the flames of lights at night appear redder

in proportion to their distance from the eye.—

Note F.

84.

Candle-light at night acts as yellow when seen

near ; we can perceive this by the effect it pro
duces on other colours . At night a pale yellow
is hardly to be distinguished from white ; blue

approaches to green, and rose- colour to orange .

85.

Candle-light at twilight acts powerfully as a

yellow light : this is best proved by the purple
blue shadows which, under these circumstances ,
are evoked by the eye.

86.

The retina may be so excited by a strong

light that it cannot perceive fainter lights ( 11 ) :
if it perceive these they appear coloured : hence
candle-light by day appears reddish, thus re
sembling, in its relation to fuller light, the spec
trum of a dazzling object ; nay, if at night we
look long and intently on the flame of alight,
it appears to increase in redness .

87.

There are faint lights which, notwithstanding

their moderate lustre, give an impression of a
40 FAINT LIGHTS .

white, or, at the most, of a light yellow appear

ance on the retina ; such as the moon in its full

splendour . Rotten wood has even a kind of

bluish light . All this will hereafter be the

subject of further remarks .

88.

If at night we place a light near a white or

greyish wall so that the surface be illumined
from this central point to some extent, we find ,
on observing the spreading light at some dis
tance, that the boundary of the illumined surface
appears to be surrounded with a yellow circle,
which on the outside tends to red-yellow. We
thus observe that when light direct or reflected
does not act in its full force, it gives an impres

sion of yellow, of reddish , and lastly even of red .

Here we find the transition to halos which we
are accustomed to see in some mode or other
round luminous points .

VIII .

SUBJECTIVE HALOS.

89.

HALOS may be divided into subjective and ob

jective. The latter will be considered under the
physical colours ; the first only belong here.
These are distinguished from the objective
 SUBJECTIVE HALOS . 41

halos by the circumstance of their vanishing

when the point of light which produces them on
the retina is covered.

90.

We have before noticed the impression of a

luminous object on the retina, and seen that it

appears larger : but the effect is not at an end

here, it is not confined to the impression of the

image ; an expansive action also takes place,

spreading from the centre.

91 .

That a nimbus of this kind is produced round

the luminous image in the eye may be best seen
in a dark room, if we look towards a moderately
large opening in the window- shutter. In this
case the bright image is surrounded by a cir-
cular misty light. I saw such a halo bounded
by a yellow and yellow- red circle on opening
my eyes at dawn, on an occasion when I passed
several nights in a bed-carriage.

92.

Halos appear most vivid when the eye is sus-

ceptible from having been in a state of repose.
A dark background also heightens their ap-
pearance. Both causes account for our seeing
them so strong if a light is presented to the eyes

UNIVERSITY
OF
OXFORD
42 SUBJECTIVE HALOS.

on waking at night. These conditions were

combined when Descartes after sleeping , as he
sat in a ship, remarked such a vividly -coloured
halo round the light.

93.

A light must shine moderately , not dazzle, in

order to produce the impression of a halo in the
eye ; at all events the halos of dazzling lights
cannot be observed . We see a splendour of
this kind round the image of the sun reflected
from the surface of water.

94 .

A halo ofthis description, attentively observed ,

is found to be encircled towards its edge with a

yellow border : but even here the expansive

action, before alluded to , is not at an end , but
appears still to extend in varied circles .

95 .

Several cases seem to indicate a circular ac-

tion of the retina, whether owing to the round

form of the eye itself and its different parts, or
to some other cause .

96.

If the eye is pressed only in a slight degree

from the inner corner, darker or lighter circles
 SUBJECTIVE HALOS . 43

appear. At night, even without pressure, we

can sometimes perceive a succession of such
circles emerging from , or spreading over, each
other.

97.

We have already seen that a yellow border is

apparent round the white space illumined by a
light placed near it. This may be a kind of
objective halo. (88. )

98 .

Subjective halos may be considered as the

result of a conflict between the light and a living
surface. From the conflict between the excit-

ing principle and the excited , an undulating

motion arises, which may be illustrated by a
comparison with the circles on water. The

stone thrown in drives the water in all direc-

tions ; the effect attains a maximum , it reacts ,

and being opposed , continues under the surface.
The effect goes on , culminates again, and thus
the circles are repeated . If we have ever re-
marked the concentric rings which appear in a

glass of water on trying to produce a tone by

rubbing the edge ; if we call to mind the inter-
mitting pulsations in the reverberations of bells,

we shall approach a conception of what may

take place on the retina when the image of a
luminous object impinges on it, not to mention
44 SUBJECTIVE HALOS.

that as a living and elastic structure, it has al

ready a circular principle in its organisation.
Note G.

99.

The bright circular space which appears

round the shining object is yellow, ending in

red : then follows a greenish circle, which is
terminated by a red border. This appears to be
the usual phenomenon where the luminous body
is somewhat considerable in size . These halos

become greater the more distant we are from

the luminous object.

100.

Halos may, however, appear extremely small

and numerous when the impinging image is
minute, yet powerful , in its effect . The ex
periment is best made with a piece of gold-leaf
placed on the ground and illumined by the sun.
In these cases the halos appear in variegated
rays . The iridescent appearance produced in
the eye when the sun pierces through the leaves
of trees seems also to belong to the same class
of phenomena .
 45

PATHOLOGICAL COLOURS .

APPENDIX .

101 .

We are now sufficiently acquainted with the

physiological colours to distinguish them from
the pathological . We know what appearances
belong to the eye in a healthy state, and are ne
cessary to enable the organ to exert its complete
vitality and activity.

102 .

Morbid phenomena indicate in like manner

the existence of organic and physical laws : for
if a living being deviates from those rules with
reference to which it is constructed , it still seeks
to agree with the general vitality of nature in
conformity with general laws, and throughout its
whole course still proves the constancy of those
principles on which the universe has existed ,

and by which it is held together.

103 .

We will here first advert to a very remarkable

state in which the vision of many persons is

found to be. As it presents a deviation from

the ordinary mode of seeing colours , it might

be fairly classed under morbid impressions ; but

as it is consistent in itself, as it often occurs,
46 PATHOLOGICAL COLOURS .

may extend to several members of a family, and

probably does not admit of cure, we may con
sider it as bordering only on the nosological
cases, and therefore place it first.

104.

I was acquainted with two individuals not

more than twenty years of age, who were thus

affected both had bluish-grey eyes, an acute
sight for near and distant objects, by day-light
and candle -light, and their mode of seeing
colours was in the main quite similar.

105 .

They agreed with the rest of the world in

denominating white, black, and grey in the usual
manner. Both saw white untinged with any
hue. One saw a somewhat brownish appear

ance in black, and in grey a somewhat reddish

tinge. In general they appeared to have a very
delicate perception of the gradations of light
and dark .

106 .

They appeared to see yellow, red -yellow, and

yellow -red , * like others : in the last case they said
they saw the yellow passing as it were over the
red as if glazed some thickly-ground carmine,
which had dried in a saucer, they called red.

* It has been found necessary to follow the author's nomencla

ture throughout. —T.
 PATHOLOGICAL COLOURS . 47

107 .

But now a striking difference presented itself.

If the carmine was passed thinly over the white
saucer, they would compare the light colour thus
produced to the colour of the sky , and call it
blue . If a rose was shown them beside it, they
would , in like manner, call it blue ; and in all the
trials which were made, it appeared that they
could not distinguish light blue from rose- colour.
They confounded rose -colour, blue, and violet on
all occasions : these colours only appeared to

them to be distinguished from each other by de

licate shades of lighter, darker, intenser, or
fainter appearance .

108 .

Again they could not distinguish green from

dark orange, nor, more especially, from a red
brown.

109.

If any one, accidentally conversing with these

individuals , happened to question them about
surrounding objects , their answers occasioned

the greatest perplexity, and the interrogator

began to fancy his own wits were out of order.
With some method we may, however, approach
to a nearer knowledge of the law of this devia
tion from the general law.
48 PATHOLOGICAL COLOURS .

110.

These persons , as may be gathered from what

has been stated, saw fewer colours than other
people hence arose the confusion of different

colours. They called the sky rose-colour, and

the rose blue, or vice versa. The question now
is did they see both blue or both rose- colour ?
did they see green orange, or orange green ?

111.

This singular enigma appears to solve itself,

ifwe assume that they saw no blue, but, instead
of it, a light pure red, a rose- colour. We can
comprehend what would be the result of this by
means of the chromatic diagram.

112.

If we take away blue from the chromatic

circle we shall miss violet and green as well .

Pure red occupies the place of blue and violet,

and in again mixing with yellow the red pro-
duces orange where green should be.

113 .

Professing to be satisfied with this mode of

explanation, we have named this remarkable de-
viation from ordinary vision " Acyanoblepsia ." *

We have prepared some coloured figures for

Non-perception of blue.
 PATHOLOGICAL COLOURS . 49

its further elucidation , and in explaining these

we shall add some further details . Among the
examples will be found a landscape, coloured in
the mode in which the individuals alluded to

appeared to see nature : the sky rose- colour, and

all that should be green varying from yellow to
brown red, nearly as foliage appears to us in
autumn. *- Note H.

114 .

We now proceed to speak of morbid and other

extraordinary affections of the retina, by which

the eye may be susceptible of an appearance of

light without external light, reserving for a
future occasion the consideration of galvanic
light.

115 .

If the eye receives a blow, sparks seem to

spread from it . In some states of body, again ,
when the blood is heated , and the system much

excited, if the eye is pressed first gently, and

then more and more strongly, a dazzling and
intolerable light may be excited .

116.

If those who have been recently couched ex-

perience pain and heat in the eye, they fre-

1 It has not been thought necessary to copy the plates here

referred to.-T.
E
50 PATHOLOGICAL COLOURS .

quently see fiery flashes and sparks : these

symptoms last sometimes for a week or fortnight,
or till the pain and heat diminish .

117 .

A person suffering from ear-ache saw sparks

and balls of light in the eye during each attack,
as long as the pain lasted .

118 .

Persons suffering from worms often experience

extraordinary appearances in the eye, sometimes

sparks of fire, sometimes spectres of light, some

times frightful figures, which they cannot by an
effort of the will cease to see : sometimes these
appearances are double.

119 .

Hypochondriacs frequently see dark objects,

such as threads , hairs , spiders , flies, wasps .
These appearances also exhibit themselves in

the incipient hard cataract. Many see semi

transparent small tubes, forms like wings of
insects, bubbles of water of various sizes , which

fall slowly down , if the eye is raised : some

times these congregate together so as to resem
ble the spawn of frogs ; sometimes they appear
as complete spheres, sometimes in the form of
lenses.

120.

As light appeared , in the former instances ,

 PATHOLOGICAL COLOURS . 51

without external light, so also these images

appear without corresponding external objects .
The images are sometimes transient, sometimes

they last during the patient's life . Colour, again ,

frequently accompanies these impressions : for
hypochondriacs often see yellow- red stripes in
the eye these are generally more vivid and
numerous in the morning , or when fasting.

121 .

We have before seen that the impression of

any object may remain for a time in the eye :
this we have found to be a physiological phe-
nomenon (23) : the excessive duration of such

an impression, on the other hand , may be con-

sidered as morbid.

122.

The weaker the organ the longer the impres-

sion of the image lasts . The retina does not so

soon recover itself ; and the effect may be con-

sidered as a kind of paralysis ( 28) .

123.

This is not to be wondered at in the case of

dazzling lights. If any one looks at the sun , he

may retain the image in his eyes for several

days. Boyle relates an instance of ten years .

124 .

The same takes place, in a certain degree, with

E 2
52 PATHOLOGICAL COLOURS .

regard to objects that are not dazzling. Büsch

relates of himself that the image of an engrav

ing, complete in all its parts, was impressed on

his eye for seventeen minutes .

125.

A person inclined to fulness of blood retained

the image of a bright red calico , with white spots,

many minutes in the eye, and saw it float before

everything like a veil . It only disappeared by

rubbing the eye for some time .

126.

Scherfer observes that the red colour, which is

the consequence of a powerful impression of

light, may last for some hours .

127.

As we can produce an appearance of light on

the retina by pressure on the eyeball , so by a
gentle pressure a red colour appears, thus cor

responding with the after- image of an impression

of light .

128.

Many sick persons , on awaking, see every

thing in the colour of the morning sky, as if
through a red veil : so , if in the evening they
doze and wake again , the same appearance pre
sents itself. It remains for some minutes , and
 PATHOLOGICAL COLOURS . 53

always disappears if the eye is rubbed a little .

Red stars and balls sometimes accompany the

impression. This state may last for a consider-

able time .

129.

The aëronauts , particularly Zambeccari and

his companions, relate that they saw the moon
blood-red at the highest elevation . As they had
ascended above the vapours of the earth, through

which we see the moon and sun naturally of such

a colour, it may be suspected that this appear-
ance may be classed with the pathological co-
lours . The senses, namely, may be so influenced
by an unusual state, that the whole nervous
system , and particularly the retina , may sink
into a kind of inertness and inexcitability.
Hence it is not impossible that the moon might
act as a very subdued light, and thus produce
the impression of the red colour. The sun even
appeared blood -red to the aëronauts of Ham-
burgh.
If those who are at some elevation in a balloon

scarcely hear each other speak , may not this,

too , be attributed to the inexcitable state of the
nerves as well as to the thinness of the air ?

130.

Objects are often seen by sick persons in

variegated colours . Boyle relates an instance
54 PATHOLOGICAL COLOURS .

of a lady, who, after a fall by which an eye was

bruised , saw all objects, but especially white
objects, glittering in colours , even to an intoler
able degree .

131 .

Physicians give the name of " Chrupsia" to an

affection of the sight, occurring in typhoid ma
ladies. In these cases the patients state that

they see the boundaries of objects coloured where

light and dark meet. A change probably takes
place in the humours of the eye, through which
their achromatism is affected .

132.

In cases of milky cataract, a very turbid crys

talline lens causes the patient to see a red light.

In a case of this kind , which was treated by the
application of electricity, the red light changed
by degrees to yellow, and at last to white, when
the patient again began to distinguish objects .
These changes of themselves warranted the con
clusion that the turbid state of the lens was gra

dually approaching the transparent state. We

shall be enabled easily to trace this effect to its
source as soon as we become better acquainted
with the physical colours .

133.

If again it may be assumed that a jaundiced

 PATHOLOGICAL COLOURS . 55

patient sees through an actually yellow-coloured

humour, we are at once referred to the depart
ment of chemical colours , and it is thus evident

that we can only thoroughly investigate the

chapter of pathological colours when we have
made ourselves acquainted with the whole range
of the remaining phenomena . What has been

adduced may therefore suffice for the present,

till we resume the further consideration of this

portion of our subject.

134.

In conclusion we may, however, at once ad

vert to some peculiar states or dispositions of
the organ .

There are painters who, instead of rendering

the colours of nature, diffuse a general tone, a
warm or cold hue, over the picture. In some,
again, a predilection for certain colours displays
itself ; in others a want of feeling for harmony.

135 .

Lastly, it is also worthy of remark , that sa

vage nations, uneducated people, and children
have a great predilection for vivid colours ; that
animals are excited to rage by certain colours ;
that people of refinement avoid vivid colours in

their dress and the objects that are about them,

and seem inclined to banish them altogether
from their presence . - Note I
 56

PART II.

PHYSICAL COLOURS .

136.

We give this designation to colours which are

produced by certain material mediums : these
mediums, however, have no colour themselves,
and may be either transparent, semi- transpa
rent yet transmitting light, or altogether opaque.
The colours in question are thus produced in
the eye through such external given causes, or
are merely reflected to the eye when by what
ever means they are already produced without
us. Although we thus ascribe to them a certain

objective character, their distinctive quality still

consists in their being transient, and not to be
arrested .

137.

They are called by former investigators co

lores apparentes, fluxi, fugitivi, phantastici, falsi,
variantes. They are also called speciosi and
emphatici, on account of their striking splen
dour. They are immediately connected with
the physiological colours, and appear to have
but little more reality : for, while in the produc
 PHYSICAL COLOURS . 57

tion of the physiological colours the eye itself

was chiefly efficient, and we could only perceive
the phenomena thus evoked within ourselves ,
but not without us, we have now to consider
the fact that colours are produced in the eye by

means of colourless objects ; that we thus too

have a colourless surface before us which is

acted upon as the retina itself is, and that we

can perceive the appearance produced upon it
without us . In such a process, however, every

observation will convince us that we have to do

with colours in a progressive and mutable, but

not in a final or complete , state.

138.

Hence, in directing our attention to these

physical colours, we find it quite possible to

place an objective phenomenon beside a sub
jective one, and often by means of the union of
the two successfully to penetrate farther into
the nature of the appearance .

139 .

Thus , in the observations by which we become

acquainted with the physical colours, the eye is

not to be considered as acting alone ; nor is the

light ever to be considered in immediate relation

with the eye but we direct our attention espe

cially to the various effects produced by me
diums, those mediums being themselves colour
less .
58 PHYSICAL COLOURS .

140.

Light under these circumstances may be af-

fected by three conditions. First, when it
flashes back from the surface of a medium ; in

considering which catoptrical experiments invite

our attention . Secondly, when it passes by the

edge of a medium : the phenomena thus pro-

duced were formerly called perioptical ; we pre-

fer the term paroptical. Thirdly, when it passes

through either a merely light- transmitting or an
actually transparent body ; thus constituting a
class of appearances on which dioptrical expe-
riments are founded . We have called a fourth

class of physical colours epoptical, as the pheno-

mena exhibit themselves on the colourless sur-
face of bodies under various conditions, without
previous or actual dye (Bag ) .- Note K.

141 .

In examining these categories with reference

to our three leading divisions, according to
which we consider the phenomena of colours

in a physiological , physical, or chemical view,

we find that the catoptrical colours are closely
connected with the physiological ; the paropti-

cal are already somewhat more distinct and

independent ; the dioptrical exhibit themselves
as entirely and strictly physical, and as having
a decidedly objective character ; the epoptical ,
although still only apparent, may be considered
as the transition to the chemical colours .
 DIOPTRICAL COLOURS . 59

142 .

If we were desirous of prosecuting our investi

gation strictly in the order of nature, we ought
to proceed according to the classification which

has just been made ; but in didactic treatises it

is not of so much consequence to connect as to
duly distinguish the various divisions of a sub

ject, in order that at last, when every single

class and case has been presented to the mind,
the whole may be embraced in one comprehen
sive view. We therefore turn our attention forth

with to the dioptrical class, in order at once to

give the reader the full impression of the phy
sical colours , and to exhibit their characteristics
the more strikingly .

IX .

DIOPTRICAL COLOURS .

143 .

COLOURS are called dioptrical when a colour

less medium is necessary to produce them ; the
medium must be such that light and darkness
can act through it either on the eye or on oppo
site surfaces. It is thus required that the me
dium should be transparent, or at least capable,
to a certain degree , of transmitting light .
60 DIOPTRICAL COLOURS OF THE FIRST CLASS .

144 .

According to these conditions we divide the

dioptrical phenomena into two classes , placing

in the first those which are produced by means

of imperfectly transparent, yet light- transmit

ting mediums ; and in the second such as are
exhibited when the medium is in the highest
degree transparent .

X.

DIOPTRICAL COLOURS OF THE FIRST CLASS .

145 .

SPACE , if we assume it to be empty, would

have the quality of absolute transparency to
our vision . If this space is filled so that the
eye cannot perceive that it is so, there exists a

more or less material transparent medium,

which may be of the nature of air and gas, may
be fluid or even solid.

146 .

The pure and light-transmitting semi -trans

parent medium is only an accumulated form of

the transparent medium. It may therefore be

presented to us in three modes .
 DIOPTRICAL COLOURS OF THE FIRST CLASS . 61

147.

The extreme degree of this accumulation is

white ; the simplest , brightest , first, opaque

occupation of space.

148.

Transparency itself, empirically considered ,

is already the first degree of the opposite state .
The intermediate degrees from this point to
opaque white are infinite.

149 .

At whatever point short of opacity we arrest

the thickening medium, it exhibits simple and
remarkable phenomena when placed in relation
with light and darkness.

150.

The highest degree of light , such as that of

the sun, of phosphorus burning in oxygen , is
dazzling and colourless : so the light of the
fixed stars is for the most part colourless . This
light, however, seen through a medium but very
slightly thickened , appears to us yellow. If the
density of such a medium be increased , or if its
volume become greater, we shall see the light
gradually assume a yellow-red hue, which at
last deepens to a ruby- colour.- Note L.
62 DIOPTRICAL COLOURS OF THE FIRST CLASS .

151.

If on the other hand darkness is seen through

a semi-transparent medium , which is itself illu

mined by a light striking on it, a blue colour

appears this becomes lighter and paler as the

density of the medium is increased , but on the

contrary appears darker and deeper the more
transparent the medium becomes : in the least

degree of dimness short of absolute transpa

rence, always supposing a perfectly colourless

medium, this deep blue approaches the most

beautiful violet.

152.

If this effect takes place in the eye as here de

scribed, and may thus be pronounced to be sub

jective, it remains further to convince ourselves
of this by objective phenomena. For a light
thus mitigated and subdued illumines all objects
in like manner with a yellow, yellow-red , or
red hue ; and, although the effect of darkness
through the non-transparent medium does not
exhibit itself so powerfully , yet the blue sky
displays itself in the camera obscura very dis
tinctly on white paper, as well as every other
material colour.

153.

In examining the cases in which this impor

 DIOPTRICAL COLOURS OF THE FIRST CLASS . 63

tant leading phenomenon appears, we naturally

mention the atmospheric colours first : most of
these may be here introduced in order.

154.

The sun seen through a certain degree of

vapour appears with a yellow disk ; the centre

is often dazzlingly yellow when the edges are

already red . The orb seen through a thick
yellow mist appears ruby- red (as was the case
in 1794, even in the north) ; the same appear
ance is still more decided , owing to the state of

the atmosphere, when the scirocco prevails in

southern climates : the clouds generally sur
rounding the sun in the latter case are of the
same colour, which is reflected again on all
objects .
The red hues of morning and evening are
owing to the same cause. The sun is announced

by a red light, in shining through a greater mass

of vapours. The higher he rises, the yellower
and brighter the light becomes.

155 .

If the darkness of infinite space is seen through

atmospheric vapours illumined by the day-light,
the blue colour appears. On high mountains
the sky appears by day intensely blue, owing to
the few thin vapours that float before the end
less dark space : as soon as we descend in the
64 DIOPTRICAL COLOURS OF THE FIRST CLASS .

valleys, the blue becomes lighter ; till at last, in

certain regions , and in consequence of increasing

vapours, it altogether changes to a very pale

blue.

156.

The mountains , in like manner, appear to us

blue ; for, as we see them at so great a distance

that we no longer distinguish the local tints,
and as no light reflected from their surface acts
on our vision , they are equivalent to mere dark
objects, which, owing to the interposed vapours ,
appear blue.

157 .

So we find the shadowed parts of nearer ob

jects are blue when the air is charged with thin

vapours .

158.

The snow- mountains, on the other hand , at a

great distance, still appear white, or approaching

to a yellowish hue, because they act on our eyes
as brightness seen through atmospheric vapour.

159.

The blue appearance at the lower part of the

flame of a candle belongs to the same class of
phenomena. If the flame be held before a white
ground, no blue will be seen , but this colour
will immediately appear if the flame is opposed
 DIOPTRICAL COLOURS OF THE FIRST CLASS . 65

to a black ground . This phenomenon may be

exhibited most strikingly with a spoonful of
lighted spirits of wine . We may thus consider

the lower part of the flame as equivalent to the

vapour which, although infinitely thin, is still
apparent before the dark surface ; it is so thin ,
that one may easily see to read through it : on
the other hand, the point of the flame which
conceals objects from our sight is to be consi
dered as a self- illuminating body.

160.

Lastly, smoke is also to be considered as a

semi-transparent medium, which appears to us
yellow or reddish before a light ground , but blue
before a dark one.

161 .

If we now turn our attention to fluid mediums,

we find that water, deprived in a very slight

degree of its transparency , produces the same
effects .

162.

The infusion of the lignum nephriticum (gui

landina Linnæi ) , which formerly excited so much

attention , is only a semi- transparent liquor,
which in dark wooden cups must appear blue,
but held towards the sun in a transparent glass
must exhibit a yellow appearance .
F
66 DIOPTRICAL COLOURS OF THE FIRST CLASS .

163 .

A drop of scented water, of spirit varnish, of

several metallic solutions , may be employed to

give various degrees of opacity to water for such

experiments . Spirit of soap perhaps answers
best.

164.

The bottom of the sea appears to divers of a

red colour in bright sunshine : in this case the
water, owing to its depth , acts as a semi -trans-
parent medium. Under these circumstances ,

they find the shadows green, which is the com-

plemental colour .

165 .

Among solid mediums the opal attracts our

attention first : its colours are, at least, partly

to be explained by the circumstance that it is ,

in fact, a semi-transparent medium, through
which sometimes light, sometimes dark, sub-
strata are visible .

166.

For these experiments , however, the opal-

glass (vitrum astroides , girasole) is the most
desirable material . It is prepared in various

ways, and its semi- opacity is produced by me-

tallic oxydes . The same effect is produced also
by melting pulverised and calcined bones toge-
 DIOPTRICAL COLOURS OF THE FIRST CLASS . 67

ther with the glass , on which account it is also

known by the name of beinglas ; but, prepared
in this mode, it easily becomes too opaque.

167 .

This glass may be adapted for experiments in

various ways : it may either be made in a very
slight degree non-transparent, in which case the

light seen through various layers placed one

upon the other may be deepened from the lightest
yellow to the deepest red , or , if made originally
more opaque , it may be employed in thinner or

thicker laminæ . The experiments may be suc

cessfully made in both ways : in order, however,

to see the bright blue colour, the glass should
neither be too opaque nor too thick. For, as it
is quite natural that darkness must act weakly
through the semi - transparent medium, so this
medium, if too thick, soon approaches whiteness .

168 .

Panes of glass throw a yellow light on objects

through those parts where they happen to be
semi-opaque, and these same parts appear blue
if we look at a dark object through them.

169 .

Smoked glass may be also mentioned here,

and is, in like manner, to be considered as a
semi-opaque medium . It exhibits the sun more
F 2
68 DIOPTRICAL COLOURS OF THE FIRST CLASS.

or less ruby- coloured ; and , although this appear

ance may be attributed to the black-brown

colour of the soot, we may still convince our

selves that a semi-transparent medium here acts

if we hold such a glass moderately smoked , and
lit by the sun on the unsmoked side , before a
dark object, for we shall then perceive a bluish
appearance.

170.

A striking experiment may be made in a

dark room with sheets of parchment. If we
fasten a piece of parchment before the opening
in the window-shutter when the sun shines , it

will appear nearly white ; by adding a second ,

a yellowish colour appears , which still increases
as more leaves are added , till at last it changes
to red.

171 .

A similar effect, owing to the state of the

crystalline lens in milky cataract, has been

already adverted to ( 131) .

172.

Having now, in tracing these phenomena,

arrived at the effect of a degree of opacity

scarcely capable of transmitting light, we may

here mention a singular appearance which was
owing to a momentary state of this kind.
 DIOPTRICAL COLOURS OF THE FIRST CLASS . 69

A portrait of a celebrated theologian had

been painted some years before the circum-
stance to which we allude, by an artist who
was known to have considerable skill in the

management of his materials . The very reve-

rend individual was represented in a rich velvet
dress, which was not a little admired , and which

attracted the eye of the spectator almost more

than the face. The picture, however, from the
effect of the smoke of lamps and dust, had lost
much of its original vivacity. It was, therefore,
placed in the hands of a painter, who was to
clean it, and give it a fresh coat of varnish .
This person began his operations by carefully
washing the picture with a sponge : no

sooner, however, had he gone over the surface

once or twice, and wiped away the first dirt,

than to his amazement the black velvet dress

changed suddenly to a light blue plush, which

gave the ecclesiastic a very secular, though some-
what old-fashioned , appearance . The painter
did not venture to go on with his washing : he
could not comprehend how a light blue should
be the ground of the deepest black, still less
how he could so suddenly have removed a glaz-
ing colour capable of converting the one tint
to the other.
At all events, he was not a little disconcerted

at having spoilt the picture to such an extent .

Nothing to characterize the ecclesiastic re-
70 DIOPTRICAL COLOURS OF THE FIRST CLASS .

mained but the richly- curled round wig, which

made the exchange of a faded plush for a hand
some new velvet dress far from desirable .

Meanwhile, the mischief appeared irreparable,

and the good artist, having turned the picture to
the wall, retired to rest with a mind ill at ease .
But what was his joy the next morning, when ,
on examining the picture, he beheld the black
velvet dress again in its full splendour. He
could not refrain from again wetting a corner,

upon which the blue colour again appeared, and

after a time vanished . On hearing of this phe
nomenon , I went at once to see the miraculous

picture . A wet sponge was passed over it in

my presence, and the change quickly took place .
I saw a somewhat faded, but decidedly light

blue plush dress , the folds under the arm being

indicated by some brown strokes.
I explained this appearance to myself by the
doctrine of the semi-opaque medium. The

painter, in order to give additional depth to his

black, may have passed some particular varnish
over it on being washed , this varnish imbibed
some moisture, and hence became semi - opaque ,
in consequence of which the black underneath

immediately appeared blue. Perhaps those

who are practically acquainted with the effect

of varnishes may, through accident or con

trivance, arrive at some means of exhibiting this
singular appearance, as an experiment, to those
 DIOPTRICAL COLOURS OF THE FIRST CLASS. 71

who are fond of investigating natural pheno

mena . Notwithstanding many attempts, I

could not myself succeed in re- producing it.

173 .

Having now traced the most splendid in

stances of atmospheric appearances, as well as

other less striking yet sufficiently remarkable

cases, to the leading examples of semi-trans
parent mediums , we have no doubt that atten
tive observers of nature will carry such re
searches further, and accustom themselves to
trace and explain the various appearances

which present themselves in every-day experi

ence on the same principle : we may also hope
that such investigators will provide themselves
with an adequate apparatus in order to place
remarkable facts before the eyes of others who
may be desirous of information .

174 .

We venture, once for all, to call the leading

appearance in question, as generally described
in the foregoing pages , a primordial and ele
mentary phenomenon ; and we may here be
permitted at once to state what we understand
by the term .
175.
The circumstances which come under our notice

in ordinary observation are , for the most part, in

sulated cases , which, with some attention , admit
72 DIOPTRICAL COLOURS OF THE FIRST CLASS .

of being classed under general leading facts.

These again range themselves under theoretical
rubrics which are more comprehensive, and
through which we become better acquainted
with certain indispensable conditions of appear-
ances in detail. From henceforth everything is
gradually arranged under higher rules and laws,
which, however, are not to be made intelligible

by words and hypotheses to the understanding

merely, but, at the same time, by real phenomena
to the senses. We call these primordial phe-
nomena, because nothing appreciable by the
senses lies beyond them, on the contrary, they

are perfectly fit to be considered as a fixed point

to which we first ascended , step by step , and

from which we may, in like manner, descend to

the commonest case of every-day experience.
Such an original phenomenon is that which has
lately engaged our attention. We see on the
one side light, brightness ; on the other dark-

ness, obscurity : we bring the semi- transparent

medium between the two , and from these con-

trasts and this medium the colours develop

themselves , contrasted , in like manner, but soon,

through a reciprocal relation , directly tending

again to a point of union . *

* That is ( according to the author's statement 150.151 . ) both

tend to red ; the yellow deepening to orange as the comparatively
dark medium is thickened before brightness ; the blue deepening
to violet as the light medium is thinned before darkness. - T.
 DIOPTRICAL COLOURS OF THE FIRST CLASS . 73

176.

With this conviction we look upon the mistake

that has been committed in the investigation of

this subject to be a very serious one, inasmuch

as a secondary phenomenon has been thus

placed higher in order-the primordial phe-

nomenon has been degraded to an inferior place ;
nay, the secondary phenomenon has been placed
at the head, a compound effect has been treated

as simple, a simple appearance as compound :

owing to this contradiction , the most capricious
complication and perplexity have been intro-

duced into physical inquiries, the effects of

which are still apparent .

177.

But when even such a primordial phenomenon

is arrived at, the evil still is that we refuse to
recognise it as such, that we still aim at some-
thing beyond, although it would become us to
confess that we are arrived at the limits of ex-
perimental knowledge. Let the observer of
nature suffer the primordial phenomenon to re-
main undisturbed in its beauty ; let the phi-

losopher admit it into his department, and he

will find that important elementary facts are a
worthier basis for further operations than insu-
lated cases, opinions, and hypotheses . Note M.
76 DIOPTRICAL COLOURS

tention was called to the degree of opacity in

the medium .

183.

Thus the different degrees of opacity in so

called transparent mediums, nay, even other

physical and chemical properties belonging to
them , are known to our vision by means of re
fraction, and invite us to make further trials in
order to penetrate more completely by physical
and chemical means into those secrets which are

already opened to our view on one side.

184.

Objects seen through mediums more or less

transparent do not appear to us in the place
which they should occupy according to the laws
of perspective . On this fact the dioptrical

colours of the second class depend .

185 .

Those laws of vision which admit of being

expressed in mathematical formulæ are based on

the principle that, as light proceeds in straight
lines, it must be possible to draw a straight line
from the eye to any given object in order that it
be seen . If, therefore, a case arises in which
the light arrives to us in a bent or broken line,
that we see the object by means of a bent or
broken line , we are at once informed that the
 OF THE SECOND CLASS .- REFRACTION . 77

medium between the eye and the object is

denser, or that it has assumed this or that

foreign nature.

186.

This deviation from the law of right-lined

vision is known by the general term of refrac

tion ; and, although we may take it for granted
that our readers are sufficiently acquainted with
its effects, yet we will here once more briefly
exhibit it in its objective and subjective point
of view .

187 .

Let the sun shine diagonally into an empty

cubical vessel, so that the opposite side be il
lumined , but not the bottom : let water be then
poured into this vessel, and the direction of the

light will be immediately altered ; for a part of

the bottom is shone upon . At the point where
the light enters the thicker medium it deviates
from its rectilinear direction , and appears broken :

hence the phenomenon is called the breaking

(brechung) or refraction . Thus much of the

objective experiment.

188.

We arrive at the subjective fact in the follow

ing mode :---Let the eye be substituted for the
sun let the sight be directed in like manner
80 REFRACTION WITHOUT

194.

And now, in order to conduct our observations

with as much exactness as possible , and to avoid

all confusion and ambiguity, we confine ourselves
at first to

SUBJECTIVE EXPERIMENTS ,

in which, namely, the object is seen by the ob

server through a refracting medium . As soon
as we have treated these in due series , the ob
jective experiments will follow in similar order.

XII.

REFRACTION WITHOUT THE APPEARANCE OF COLOUR.

195 .

REFRACTION can visibly take place without our

perceiving an appearance of colour . To what

ever extent a colourless or uniformly coloured

surface may be altered as to its position by re
fraction, no colour consequent upon refraction
appears within it, provided it has no outline or
boundary. We may convince ourselves of this
in various ways .
 THE APPEARANCE OF COLOUR. 81

196 .

Place a glass cube on any larger surface ,

and look through the glass perpendicularly or
obliquely, the unbroken surface opposite the eye
appears altogether raised, but no colour exhibits

itself. If we look at a pure grey or blue sky or

a uniformly white or coloured wall through a
prism , the portion of the surface which the eye
thus embraces will be altogether changed as to

its position, without our therefore observing the

smallest appearance of colour.

XIII.

CONDITIONS OF THE APPEARANCE OF COLOUR.

197 .

ALTHOUGH in the foregoing experiments we

have found all unbroken surfaces, large or small ,

colourless , yet at the outlines or boundaries ,

where the surface is relieved upon a darker or
lighter object, we observe a coloured appearance .

198 .

Outline, as well as surface, is necessary to

constitute a figure or circumscribed object. We

therefore express the leading fact thus : circum
scribed objects must be displaced by refraction
in order to the exhibition of an appearance of
colour.
G
82 CONDITIONS OF

199.

We place before us the simplest object, a light

disk on a dark ground (A) . * A displacement
occurs with regard to this object, if we appa
rently extend its outline from the centre by mag

nifying it. This may be done with any convex

glass , and in this case we see a blue edge ( B) .

200.

We can, to appearance , contract the circum

ference of the same light disk towards the centre
by diminishing the object ; the edge will then
appear yellow (c) . This may be done with a
concave glass , which, however, should not be

ground thin like common eye-glasses, but must

have some substance. In order, however, to
make this experiment at once with the convex
glass, let a smaller black disk be inserted within
the light disk on a black ground . If we magnify
the black disk on a white ground with a con

vex glass, the same result takes place as if we

diminished the white disk ; for we extend the
black outline upon the white, and we thus per
ceive the yellow edge together with the blue
edge (D) .
201 .

These two appearances, the blue and yellow,

exhibit themselves in and upon the white : they

* Plate 2, fig. 1 .
 Fig 1. 11.

D A B

Fig 2. Fig 3.

b a a

Fig 4 Fig 5

72
1
 THE APPEARANCE OF COLOUR . 83

both assume a reddish hue , in proportion as

they mingle with the black . *

202 .

In this short statement we have described the

primordial phenomena of all appearance of co

lour occasioned by refraction . These undoubt
edly may be repeated, varied, and rendered

more striking ; may be combined , complicated ,

confused ; but, after all , may be still restored
to their original simplicity .

203 .

In examining the process of the experiment

just given, we find that in the one case we have,
to appearance, extended the white edge upon the
dark surface ; in the other we have extended the

dark edge upon the white surface, supplanting

one by the other, pushing one over the other.
We will now endeavour, step by step, to analyse
these and similar cases.

204.

If we cause the white disk to move, in appear

ance, entirely from its place, which can be done

* The author has omitted the orange and purple in the co

loured diagrams which illustrate these first experiments, from a
wish probably to present the elementary contrast, on which he
lays a stress, in greater simplicity. The reddish tinge would be
apparent, as stated above, where the blue and yellow are in con
tact with the black.- T.
G 2
84 CONDITIONS OF

effectually by prisms, it will be coloured ac

cording to the direction in which it apparently
moves, in conformity with the above laws . If
we look at the disk a * through a prism, so that
it appear moved to b, the outer edge will
appear blue and blue-red , according to the law
of the figure в (fig. 1 ) , the other edge being
yellow, and yellow-red , according to the law of
the figure c (fig. 1) . For in the first case the
white figure is, as it were, extended over the
dark boundary, and in the other case the dark
boundary is passed over the white figure . The
same happens if the disk is, to appearance ,
moved from a to c , from a to d, and so throughout
the circle.

205.

As it is with the simple effect, so it is with

more complicated appearances . If we look

through a horizontal prism ( ab† ) at a white disk

placed at some distance behind it at e, the disk
will be raised to f, and coloured according to
the above law. If we remove this prism , and
look through a vertical one (cd) at the same
disk, it will appear at h, and coloured accord
ing to the same law. If we place the two
prisms one upon the other, the disk will appear
displaced diagonally, in conformity with a ge
neral law of nature , and will be coloured as

* Plate 2, fig. 2. + Plate 2 , fig. 4.

 THE APPEARANCE OF COLOUR. 85

before ; that is , according to its movement in the

direction , e. g.: *

206 .

If we attentively examine these opposite co-

loured edges , we find that they only appear in
the direction of the apparent change of place .
A round figure leaves us in some degree uncer-
tain as to this : a quadrangular figure removes
all doubt.

207.

The quadrangular figure a, † moved in the

direction ab, or ad, exhibits no colour on the
sides which are parallel with the direction in
which it moves : on the other hand , if moved
in the direction a c, parallel with its diagonal ,
all the edges of the figure appear coloured . ‡

208.

Thus, a former position (203) is here con-

firmed ; viz . to produce colour, an object must
be so displaced that the light edges be appa-
rently carried over a dark surface, the dark
edges over a light surface, the figure over its
boundary, the boundary over the figure . But

* In this case, according to the author, the refracting medium

being increased in mass, the appearance of colour is increased ,
and the displacement is greater.-T.
† Plate 2, fig. 3.
Fig. 2, plate 1 , contains a variety of forms, which, when
viewed through a prism, are intended to illustrate the statement
in this and the following paragraph .
86 CONDITIONS UNDER WHICH THE

if the rectilinear boundaries of a figure could be

indefinitely extended by refraction , so that figure

and background might only pursue their course
next, but not over each other, no colour would
appear, not even if they were prolonged to
infinity.

XIV .

CONDITIONS UNDER WHICH THE APPEARANCE OF

COLOUR INCREASES .

209 .
We have seen in the foregoing experiments

that all appearance of colour occasioned by re

fraction depends on the condition that the
boundary or edge be moved in upon the object
itself, or the object itself over the ground , that
the figure should be, as it were, carried over
itself, or over the ground . And we shall now
find that, by increased displacement of the object,
the appearance of colour exhibits itself in a

greater degree. This takes place in subjective

experiments , to which, for the present, we con
fine ourselves, under the following conditions .

210.

First , if, in looking through parallel mediums ,

the eye is directed more obliquely .

Secondly , if the surfaces of the medium are

no longer parallel , but form a more or less acute
angle.
 APPEARANCE OF COLOUR INCREASES. 87

Thirdly, owing to the increased proportion of

the medium , whether parallel mediums be in
creased in size, or whether the angle be in
creased , provided it does not attain a right angle.
Fourthly, owing to the distance of the eye
armed with a refracting medium from the object
to be displaced .

Fifthly, owing to a chemical property that

may be communicated to the glass , and which
may be afterwards increased in effect.

211 .

The greatest change of place, short of consi

derable distortion of the object, is produced by
means of prisms, and this is the reason why the
appearance of colour can be exhibited most

powerfully through glasses of this form. Yet

we will not, in employing them, suffer ourselves
to be dazzled by the splendid appearances they
exhibit, but keep the above well -established,
simple principles calmly in view.

212 .

The colour which is outside, or foremost, in

the apparent change of an object by refraction ,
is always the broader, and we will henceforth
call this a border : the colour that remains next

the outline is the narrower, and this we will call

an edge.
88 CONDITIONS UNDER WHICH THE

213 .

If we move a dark boundary towards a light

surface, the yellow broader border is foremost ,
and the narrower yellow- red edge follows close
to the outline. If we move a light boundary
towards a dark surface , the broader violet border

is foremost, and the narrower blue edge follows.

214.

If the object is large, its centre remains un

coloured . Its inner surface is then to be consi

dered as unlimited (195 ) : it is displaced , but

not otherwise altered : but if the object is so
narrow, that under the above conditions the

yellow border can reach the blue edge , the space

between the outlines will be entirely covered
with colour. If we make this experiment with
a white stripe on a black ground , * the two ex
tremes will presently meet, and thus produce
green . We shall then see the following series
of colours :
Yellow-red .
Yellow.
Green .
Blue.
Blue-red .

215 .

If we place a black band, or stripe, on white

paper, the violet border will spread till it meets

* Plate 2, fig. 5, left. + Plate 2, fig. 5, right.

 APPEARANCE OF COLOUR INCREASES . 89

the yellow-red edge . In this case the inter

mediate black is effaced (as the intermediate

white was in the last experiment), and in its
stead a splendid pure red will appear. * The
series of colours will now be as follows :
· Blue.
Blue-red .
Red .
Yellow-red .
Yellow.

216.

The yellow and blue, in the first case (214) ,

can by degrees meet so fully, that the two
colours blend entirely in green, and the order
will then be,
Yellow- red .
Green.
Blue-red .

In the second case (215) , under similar cir

cumstances , we see only
Blue.
Red .
Yellow.

This appearance is best exhibited by refract

ing the bars of a window when they are relieved
on a grey sky .†

* This pure red, the union of orange and violet, is considered

by the author the maximum of the coloured appearance : he has
appropriated the term purpur to it . See paragraph 703, and
note.-T.
+ The bands or stripes in fig. 4 , plate 1 , when viewed through
a prism, exhibit the colours represented in plate 2, fig. 5.
90 EXPLANATION OF THE FOREGOING PHENOMENA.

217.

In all this we are never to forget that this

appearance is not to be considered as a complete
or final state, but always as a progressive, in- •

creasing, and, in many senses, controllable ap-

pearance. Thus we find that, by the negation
of the above five conditions, it gradually de-
creases, and at last disappears altogether.

XV.

EXPLANATION OF THE FOREGOING PHENOMENA.

218.

BEFORE we proceed further, it is incumbent on

us to explain the first tolerably simple pheno-
menon, and to show its connexion with the

principles first laid down , in order that the ob-

server of nature may be enabled clearly to com-
prehend the more complicated appearances that
follow.

219.

In the first place, it is necessary to remember

that we have to do with circumscribed objects.
In the act of seeing, generally, it is the circum-
scribed visible which chiefly invites our obser-
vation ; and in the present instance, in speak-
ing of the appearance of colour , as occasioned
by refraction , the circumscribed visible , the de-
tached object solely occupies our attention .
 EXPLANATION OF THE FOREGOING PHENOMENA. 91

220 .

For our chromatic exhibitions we can , how-

ever, divide objects generally into primary and

secondary. The expressions of themselves de-

note what we understand by them, but our

meaning will be rendered still more plain by
what follows.

221 .

Primary objects may be considered firstly as

original, as images which are impressed on the
eye by things before it, and which assure us of
their reality . To these the secondary images
may be opposed as derived images, which remain

in the organ when the object itself is taken

away ; those apparent after- images , which have

been circumstantially treated of in the doctrine

of physiological colours .

222.

The primary images, again , may be consi-

dered as direct images , which , like the original
impressions, are conveyed immediately from the
object to the eye . In contradistinction to these ,
the secondary images may be considered as in-
direct, being only conveyed to us, as it were, at
second-hand from a reflecting surface. These
are the mirrored , or catoptrical, images, which
in certain cases can also become double images :

223.

When, namely, the reflecting body is trans-

92 EXPLANATION OF THE FOREGOING PHENOMENA.

parent, and has two parallel surfaces, one behind

the other in such a case, an image may be re-

flected to the eye from both surfaces, and thus

arise double images, inasmuch as the upper

image does not quite cover the under one : this

may take place in various ways.
Let a playing-card be held before a mirror.
We shall at first see the distinct image of the
card, but the edge of the whole card, as well as
that of every spot upon it, will be bounded on
one side with a border, which is the beginning
of the second reflection . This effect varies in

different mirrors, according to the different

thickness of the glass, and the accidents of
polishing. If a person wearing a white waist-

coat, with the remaining part of his dress dark ,

stands before certain mirrors , the border appears
very distinctly, and in like manner the metal
buttons on dark cloth exhibit the double reflec-

tion very evidently.

224.

The reader who has made himself acquainted

with our former descriptions of experiments (80)
will the more readily follow the present state-
ment. The window-bars reflected by plates of
glass appear double, and by increased thickness
of the glass, and a due adaptation of the angle
of reflection , the two reflections may be entirely

separated from each other . So a vase full of

 EXPLANATION OF THE FOREGOING PHENOMENA. 93

water, with a plane mirror-like bottom , reflects

any object twice, the two reflections being
more or less separated under the same con
ditions . In these cases it is to be observed that,
where the two reflections cover each other,
the perfect vivid image is reflected , but where
they are separated they exhibit only weak ,
transparent, and shadowy images .

225.

If we wish to know which is the under and

which the upper image, we have only to take a

coloured medium , for then a light object re
flected from the under surface is of the colour

of the medium, while that reflected from the

upper surface presents the complemental colour.

With dark objects it is the reverse ; hence black

and white surfaces may be here also conveni
ently employed. How easily the double images
assume and evoke colours will here again be
striking .

226 .

Thirdly, the primary images may be con

sidered as principal images , while the secondary
can be, as it were, annexed to these as accessory
images. Such an accessory image produces a sort
of double form ; except that it does not separate
itself from the principal object, although it may
be said to be always endeavouring to do so. It is
94 EXPLANATION OF THE FOREGOING PHENOMENA.

with secondary images of this last description

that we have to do in prismatic appearances .

227 .

A surface without a boundary exhibits no

appearance of colour when refracted ( 195 ) .
Whatever is seen must be circumscribed by an
outline to produce this effect . In other words.

a figure, an object, is required ; this object

undergoes an apparent change of place by re-
fraction the change is however not complete,
not clean, not sharp ; but incomplete, inasmuch
as an accessory image only is produced .

228 .

In examining every appearance of nature ,

but especially in examining an important and
striking one, we should not remain in one spot,
we should not confine ourselves to the insulated

fact, nor dwell on it exclusively , but look round

through all nature to see where something simi-
lar, something that has affinity to it, appears :
for it is only by combining analogies that we
gradually arrive at a whole which speaks for
itself, and requires no further explanation .

229.

Thus we here call to mind that in certain

cases refraction unquestionably produces double

images, as is the case in Iceland spar : similar
 EXPLANATION OF THE FOREGOING PHENOMENA. 95

double images are also apparent in cases of re

fraction through large rock crystals, and in
other instances ; phenomena which have not
hitherto been sufficiently observed .*

230.

But since in the case under consideration

(227) the question relates not to double but to
accessory images, we refer to a phenomenon
already adverted to, but not yet thoroughly
investigated . We allude to an earlier experi
ment, in which it appeared that a sort of con
flict took place in regard to the retina between
a light object and its dark ground, and between
a dark object and its light ground ( 16) . The
light object in this case appeared larger, the
dark one smaller.

231 .

By a more exact observation of this pheno

menon we may remark that the forms are not
sharply distinguished from the ground , but that
they appear with a kind of grey, in some de
gree, coloured edge ; in short, with an accessory
image. If, then, objects seen only with the
naked eye produce such effects , what may not
take place when a dense medium is interposed ?
It is not that alone which presents itself to us

* The date of the publication , 1810, is sometimes to be remem

bered .- T.
96 EXPLANATION OF THEe foregoing PHENOMENA.

in obvious operation which produces and suffers

effects, but likewise all principles that have a
mutual relation only of some sort are efficient
accordingly, and indeed often in a very high
degree.
232 .

Thus when refraction produces its effect on

an object there appears an accessory image
next the object itself : the real form thus re
fracted seems even to linger behind , as if resist
ing the change of place ; but the accessory image
seems to advance, and extends itself more or
less in the mode already shown (212-216 ) .

233.

We also remarked (224) that in double

images the fainter appear only half substan
tial, having a kind of transparent, evanescent
character, just as the fainter shades of double
shadows must always appear as half- shadows .
These latter assume colours easily, and produce

them readily (69) , the former also ( 80 ) ; and the

same takes place in the instance of accessory

images , which , it is true , do not altogether quit

the real object, but still advance or extend from
it as half- substantial images , and hence can ap

pear coloured so quickly and so powerfully.

234 .

That the prismatic appearance is in fact an

 EXPLANATION OF THE FOREGOING PHENOMENA. 97

accessory image we may convince ourselves in

more than one mode. It corresponds exactly

with the form of the object itself. Whether the

object be bounded by a straight line or a curve ,

indented or waving , the form of the accessory
image corresponds throughout exactly with the
form of the object. *

235.

Again, not only the form but other qualities

of the object are communicated to the accessory
image. If the object is sharply relieved from
its ground, like white on black, the coloured
accessory image in like manner appears in its
greatest force . It is vivid , distinct, and power
ful ; but it is most especially powerful when a
luminous object is shown on a dark ground ,
which may be contrived in various ways .

236 .

But if the object is but faintly distinguished

from the ground, like greyobjects on black or
white, or even on each other, the accessory

image is also faint, and, when the original differ

ence of tint or force is slight, becomes hardly
discernible .

The forms in fig. 2, plate 1 , when seen through a prism, are

again intended to exemplify this. In the plates to the original
work curvilinear figures are added, but the circles, fig . 1 , in the
same plate, may answer the same end.-T.
H
98 EXPLANATION OF THE FOREGOING PHENOMENA.

237.

The appearances which are observable when

coloured objects are relieved on light, dark , or

coloured grounds are, moreover, well worthy of
attention . In this case a union takes place
between the apparent colour of the accessory
image and the real colour of the object ; a com
pound colour is the result, which is either assisted

and enhanced by the accordance , or neutralised

by the opposition of its ingredients .

238.

But the common and general characteristic

both of the double and accessory image is semi

transparence. The tendency of a transparent

medium to become only half transparent, or
merely light- transmitting, has been before ad
verted to ( 147 , 148 ) . Let the reader assume
that he sees within or through such a medium
a visionary image, and he will at once pro
nounce this latter to be a semi-transparent image.

239.

Thus the colours produced by refraction may

be fitly explained by the doctrine of the semi

transparent mediums. For where dark passes

over light, as the border of the semi-transparent
accessory image advances , yellow appears ; and ,
on the other hand , where a light outline passes

over the dark background, blue appears ( 150,

151 ) .
 EXPLANATION OF THE FOREGOING PHENOMENA. 99

240.

The advancing foremost colour is always the

broader. Thus the yellow spreads over the light
with a broad border , but the yellow- red appears

as a narrower stripe and is next the dark, ac-

cording to the doctrine of augmentation , as an
effect of shade . *

241 .

On the opposite side the condensed blue is

next the edge, while the advancing border,

spreading as a thinner veil over the black, pro-

duces the violet colour, precisely on the princi-

ples before explained in treating of semi -trans-

parent mediums, principles which will hereafter

be found equally efficient in many other cases .

242 .

Since an analysis like the present requires to

be confirmed by ocular demonstration, we beg
every reader to make himself acquainted with
the experiments hitherto adduced, not in a
superficial manner, but fairly and thoroughly.
We have not placed arbitrary signs before him
instead of the appearances themselves ; no
modes of expression are here proposed for his

* The author has before observed that colour is a degree of

darkness, and he here means that increase of darkness, produced by
transparent mediums, is, to a certain extent, increase of colour.-T.
H 2
100 EXPLANATION OF THE FOREGOING PHENOMENA.

adoption which may be repeated for ever with-

out the exercise of thought and without leading
any one to think ; but we invite him to examine

intelligible appearances, which must be present

to the eye and mind , in order to enable him
clearly to trace these appearances to their ori-
gin, and to explain them to himself and to
others.

XVI .

DECREASE OF THE APPEARANCE OF COLOUR.

243 .

We need only take the five conditions (210)

under which the appearance of colour increases
in the contrary order, to produce the contrary or

decreasing state ; it may be as well , however,

briefly to describe and review the corresponding
modifications which are presented to the eye.

244 .

At the highest point of complete junction of

the opposite edges, the colours appear as fol-
lows ( 216) :-

Yellow-red . Blue.
Green. Red .
Blue-red. Yellow.
 DECREASE OF THE APPEARANCE OF COLOUR. 101

245 .

Where the junction is less complete, the ap

pearance is as follows ( 214 , 215 ) : —

Yellow-red . Blue .
Yellow. Blue-red.
Green. Red .
Blue. Yellow- red .
Blue-red . Yellow.

Here, therefore, the surface still appears

completely coloured , but neither series is to be

considered as an elementary series, always de
veloping itself in the same manner and in the
same degrees ; on the contrary, they can and
should be resolved into their elements ; and , in

doing this, we become better acquainted with

their nature and character.

246 .

These elements then are ( 199 , 200, 201)

Yellow- red . Blue.

Yellow. Blue-red .
White . Black.
Blue. Yellow-red .
Blue-red . Yellow.

Here the surface itself, the original object,

which has been hitherto completely covered,
and as it were lost, again appears in the centre
of the colours , asserts its right, and enables us
102 DECREASE OF THE APPEARANCE OF COLOUR.

fully to recognise the secondary nature of the

accessory images which exhibit themselves as
66
edges " and " borders ."-Note N.

247.

We can make these edges and borders as nar

row as we please ; nay, we can still have refrac

tion in reserve after having done away with all

appearance of colour at the boundary of the

object.
Having now sufficiently investigated the ex
hibition of colour in this phenomenon , we repeat
that we cannot admit it to be an elementary
phenomenon . On the contrary, we have traced
it to an antecedent and a simpler one ; we have
derived it, in connexion with the theory of se

condary images, from the primordial pheno

menon of light and darkness , as affected or acted

upon by semi-transparent mediums . Thus pre

pared, we proceed to describe the appearances
which refraction produces on grey and coloured

objects, and this will complete the section of

subjective phenomena .
 103

XVII .

GREY OBJECTS DISPLACED BY REFRACTION .

248 .

Hitherto we have confined our attention to

black and white objects relieved on respectively

opposite grounds, as seen through the prism,
because the coloured edges and borders are most
clearly displayed in such cases . We now re-

peat these experiments with grey objects , and

again find similar results .

249.

As we called black the equivalent of dark-

ness, and white the representative of light ( 18 ) ,
so we now venture to say that grey represents
half- shadow, which partakes more or less of
light and darkness, and thus stands between
the two. We invite the reader to call to mind

the following facts as bearing on our present

view.

250.

Grey objects appear lighter on a black than

on a white ground ( 33) ; they appear as a light

on a black ground , and larger ; as a dark on the
white ground, and smaller. ( 16. )
104 GREY OBJECTS DISPLACED BY REFRACTION .

251 .

The darker the grey the more it appears as

a faint light on black, as a strong dark on white,
and vice versa ; hence the accessory images of

dark-grey on black are faint, on white strong :

so the accessory images of light-grey on white
are faint, on black strong.

252.

Grey on black, seen through the prism , will

exhibit the same appearances as white on black ;
the edges are coloured according to the same
law, only the borders appear fainter. If we
relieve grey on white, we have the same edges
and borders which would be produced if we saw
black on white through the prism .- Note O.

253.

Various shades of grey placed next each

other in gradation will exhibit at their edges ,
either blue and violet only, or red and yellow

only, according as the darker grey is placed

over or under.

254 .

A series of such shades of grey placed hori-

zontally next each other will be coloured con-
formably to the same law according as the whole
series is relieved , on a black or white ground
above or below.
 GREY OBJECTS DISPLACED BY REFRACTION. 105

255.

The observer may see the phenomena ex

hibited by the prism at one glance, by enlarging
the plate intended to illustrate this section . *

256.

It is of great importance duly to examine and

consider another experiment in which a grey

object is placed partly on a black and partly on

a white surface , so that the line of division
passes vertically through the object.

257.

The colours will appear on this grey object

in conformity with the usual law, but according

to the opposite relation of the light to the dark,
and will be contrasted in a line . For as the
grey is as a light to the black, so it exhibits the

red and yellow above the blue and violet below :

again, as the grey is as a dark to the white, the
blue and violet appear above the red and yellow
below . This experiment will be found of great
importance with reference to the next chapter.

* It has been thought unnecessary to give all the examples in

the plate alluded to, but the leading instance referred to in the
next paragraph will be found in plate 3, fig. 1. The grey square
when seen through a prism will exhibit the effects described in
par. 257.-T.
 1
106 1

XVIII.

COLOURED OBJECTS DISPLACED BY REFRACTION.

258 .

An unlimited coloured surface exhibits

no prismatic colour in addition to its own hue,

thus not at all differing from a black , white, or
grey surface. To produce the appearance of
colour, light and dark boundaries must act on it
either accidentally or by contrivance. Hence
experiments and observations on coloured sur
faces, as seen through the prism , can only be
made when such surfaces are separated by an

outline from another differently tinted surface, "

in short when circumscribed objects are coloured ,

259.

All colours , whatever they may be, correspond "

so far with grey, that they appear darker than
white and lighter than black. This shade - like
quality of colour (σxspóv) has been already al
luded to (69) , and will become more and more
evident . If then we begin by placing coloured

objects on black and white surfaces, and ex

amine them through the prism, we shall again
have all that we have seen exhibited with grey
surfaces .
Fig 1. 111

Lady

Fig 2.

1
 COLOURED OBJECTS DISPLACED BY REFRACTION . 107

260.

If we displace a coloured object by refraction ,

there appears , as in the case of colourless ob

jects and according to the same laws, an acces

sory image . This accessory image retains, as
far as colour is concerned, its usual nature , and
acts on one side as a blue and blue-red , on the
opposite side as a yellow and yellow- red . Hence
the apparent colour of the edge and border will
be either homogeneous with the real colour of

the object, or not so . In the first case the ap

parent image identifies itself with the real one,

and appears to increase it, while, in the second

case, the real image may be vitiated , rendered

indistinct, and reduced in size by the apparent

image. We proceed to review the cases in

which these effects are most strikingly exhibited .

261 .

If we take a coloured drawing enlarged from

the plate, which illustrates this experiment,*

and examine the red and blue squares placed

next each other on a black ground , through the

prism as usual , we shall find that as both colours

are lighter than the ground , similarly coloured

edges and borders will appear above and below,

* Plate 3 , fig. 1. The author always recommends making the

experiments on an increased scale, in order to see the prismatic
effects distinctly.
108 COLOURED OBJECTS DISPLACED BY REFRACTION .

at the outlines of both, only they will not appear

equally distinct to the eye.

262.

Red is proportionally much lighter on black

than blue is . The colours of the edges will
therefore appear stronger on the red than on
the blue, which here acts as a dark-grey, but
little different from black. ( 251. )

263.

The extreme red edge will identify itself with

the vermilion colour of the square, which will
thus appear a little elongated in this direction ;
while the yellow border immediately underneath
it only gives the red surface a more brilliant
appearance, and is not distinguished without
attentive observation .

264 .

On the other hand the red edge and yellow

border are heterogeneous with the blue square ;
a dull red appears at the edge, and a dull green
mingles with the figure, and thus the blue
square seems, at a hasty glance, to be com-
paratively diminished on this side .

265.

At the lower outline of the two squares a blue

edge and a violet border will appear, and will
 COLOURED OBJECTS DISPLACED BY REFRACTION . 109

produce the contrary effect ; for the blue edge,

which is heterogeneous with the warm red sur-
face, will vitiate it and produce a neutral colour,
so that the red on this side appears compara-

tively reduced and driven upwards, and the

violet border on the black is scarcely percep-
tible .

266 .

On the other hand , the blue apparent edge

will identify itself with the blue square, and

not only not reduce , but extend it. The blue
edge and even the violet border next it have
the apparent effect of increasing the surface ,
and elongating it in that direction.

267 .

The effect of homogeneous and heterogeneous

edges , as I have now minutely described it, is
so powerful and singular that the two squares
at the first glance seem pushed out of their re-
lative horizontal position and moved in opposite
directions, the red upwards , the blue down-
wards . But no one who is accustomed to ob-

serve experiments in a certain succession , and

respectively to connect and trace them , will
suffer himself to be deceived by such an unreal
effect.

268 .

A just impression with regard to this import-

110 COLOURED OBJECTS DISPLACED BY REFRACTION .

ant phenomenon will , however, much depend

on some nice and even troublesome conditions ,
which are necessary to produce the illusion in
question . Paper should be tinged with vermi-
lion or the best minium for the red square, and

with deep indigo for the blue square . The blue

and red prismatic edges will then unite imper-
ceptibly with the real surfaces where they are
respectively homogeneous ; where they are not,
they vitiate the colours of the squares without
producing a very distinct middle tint. The real

red should not incline too much to yellow, other-

wise the apparent deep red edge above will be
too distinct ; at the same time it should be

somewhat yellow, otherwise the transition to the

yellow border will be too observable. The blue
must not be light, otherwise the red edge will
be visible , and the yellow border will produce
a too decided green , while the violet border
underneath would not give us the impression of
being part of an elongated light blue square .

269.

All this will be treated more circumstantially

hereafter, when we speak of the apparatus in-
tended to facilitate the experiments connected
*
with this part of our subject . Every inquirer

Neither the description of the apparatus nor the recapitula-

tion of the whole theory, so often alluded to by the author, were
ever given.—T.
 COLOURED OBJECTS DISPLACED BY REFRACTION . 111

should prepare the figures himself, in order

fairly to exhibit this specimen of ocular decep-
tion , and at the same time to convince himself
that the coloured edges, even in this case, can-
not escape accurate examination .

270.

Meanwhile various other combinations, as

exhibited in the plate, are fully calculated to

remove all doubt on this point in the mind of
every attentive observer .

271 .

If, for instance, we look at a white square ,

next the blue one, on a black ground, the pris-

matic hues of the opposite edges of the white ,
which here occupies the place of the red in the
former experiment, will exhibit themselves in
their utmost force . The red edge extends itself
above the level of the blue almost in a greater

degree than was the case with the red square

itself in the former experiment. The lower blue
edge, again, is visible in its full force next the
white , while, on the other hand, it cannot be
distinguished next the blue square . The violet
border underneath is also much more apparent
on the white than on the blue.

272.

If the observer now compares these double

112 COLOURED OBJECTS DISPLACED BY REFRACTION .

squares, carefully prepared and arranged one

above the other, the red with the white, the two
blue squares together, the blue with the red , the
blue with the white, he will clearly perceive the
relations of these surfaces to their coloured
edges and borders .

273.

The edges and their relations to the coloured

surfaces appear still more striking if we look at
the coloured squares and a black square on a
white ground ; for in this case the illusion be
fore mentioned ceases altogether, and the effect
of the edges is as visible as in any case that has
come under our observation . Let the blue and

red squares be first examined through the prism .

In both the blue edge now appears above ; this

edge, homogeneous with the blue surface, unites

with it, and appears to extend it upwards , only
the blue edge, owing to its lightness , is some
what too distinct in its upper portion ; the vio
let border underneath it is also sufficiently evi
dent on the blue. The apparent blue edge is ,

on the other hand , heterogeneous with the red

square ; it is neutralised by contrast, and is
scarcely visible ; meanwhile the violet border,
uniting with the real red, produces a hue re

sembling that of the peach-blossom .

274 .

If thus, owing to the above causes , the upper

 COLOURED OBJECTS DISPLACED BY REFRACTION . 113

outlines of these squares do not appear level

with each other, the correspondence of the
under outlines is the more observable ; for since
both colours, the red and the blue, are darks
compared with the white (as in the former case
they were light compared with the black) , the
red edge with its yellow border appears very
distinctly under both . It exhibits itself under
the warm red surface in its full force, and
under the dark blue nearly as it appears under
the black as may be seen if we compare the
edges and borders of the figures placed one
above the other on the white ground.

275.

In order to present these experiments with

the greatest variety and perspicuity, squares
of various colours are so arranged that

the boundary of the black and white passes

through them vertically . According to the

laws now known to us, especially in their appli
cation to coloured objects , we shall find the
squares as usual doubly coloured at each edge ;
each square will appear to be split in two, and

to be elongated upwards or downwards. We

may here call to mind the experiment with the
grey figure seen in like manner on the line of
division between black and white (257) . †

* Plate iii. fig. 1 .

† The grey square is introduced in the same plate, fig. 1 , above
the coloured squares .
I
114 COLOURED OBJECTS DISPLACED BY REFRACTION.

276.

A phenomenon was before exhibited , even to

illusion , in the instance of a red and blue

square on a black ground ; in the present expe

riment the elongation upwards and downwards

of two differently coloured figures is apparent

in the two halves of one and the same figure of
one and the same colour. Thus we are still re
ferred to the coloured edges and borders, and to
the effects of their homogeneous and heteroge

neous relations with respect to the real colours

of the objects .
277.

I leave it to observers themselves to compare

the various gradations of coloured squares ,

placed half on black half on white, only in

viting their attention to the apparent alteration
which takes place in contrary directions ; for
red and yellow appear elongated upwards if on
a black ground , downwards if on a white ; blue,
downwards if on a black ground , upwards if on a

white. All which, however, is quite in accordance

with the diffusely detailed examples above given.

278.

Let the observer now turn the figures so that

the before- mentioned squares placed on the line
of division between black and white may be in
a horizontal series ; the black above, the white
underneath . On looking at these squares
 COLOURED OBJECTS DISPLACED BY REFRACTION . 115

through the prism, he will observe that the red

square gains by the addition of two red edges ;
on more accurate examination he will observe

the yellow border on the red figure, and the

lower yellow border upon the white will be per
fectly apparent .

279.

The upper red edge on the blue square is

on the other hand hardly visible ; the yellow
border next it produces a dull green by mingling

with the figure ; the lower red edge and the

yellow border are displayed in lively colours.

280.

After observing that the red figure in these

cases appears to gain by an addition on both
sides , while the dark blue, on one side at least,
loses something ; we shall see the contrary
effect produced by turning the same figures up
side down, so that the white ground be above,
the black below.

281 .

For as the homogeneous edges and borders

now appear above and below the blue square,
this appears elongated , and a portion of the
surface itself seems even more brilliantly co

loured : it is only by attentive observation that

we can distinguish the edges and borders from

the colour of the figure itself.

I 2
 116 COLOURED OBJECTS DISPLACED BY REFRACTION.

282.

The yellow and red squares, on the other

hand, are comparatively reduced by the hetero
geneous edges in this position of the figures,
and their colours are, to a certain extent, vitiated .

The blue edge in both is almost invisible . The

violet border appears as a beautiful peach
blossom hue on the red, as a very pale colour of

the same kind on the yellow ; both the lower

edges are green ; dull on the red, vivid on the
yellow ; the violet border is but faintly percep
tible under the red, but is more apparent under
the yellow.

283.

Every inquirer should make it a point to be

thoroughly acquainted with all the appearances
here adduced, and not consider it irksome to
follow out a single phenomenon through so
many modifying circumstances . These expe
riments, it is true, may be multiplied to infinity
by differently coloured figures, upon and be
tween differently coloured grounds . Under all
such circumstances, however, it will be evident
to every attentive observer that coloured squares
only appear relatively altered, or elongated, or
reduced by the prism, because an addition of
homogeneous or heterogeneous edges produces
an illusion . The inquirer will now be enabled
to do away with this illusion if he has the
 COLOURED OBJECTS DISPLACED BY REFRACTION. 117

patience to go through the experiments one after

the other, always comparing the effects together,
and satisfying himself of their correspondence.
Experiments with coloured objects might
have been contrived in various ways : why they

have been exhibited precisely in the above mode,

and with so much minuteness , will be seen here
after. The phenomena , although formerly not
unknown , were much misunderstood ; and it was
necessary to investigate them thoroughly to
render some portions of our intended historical
view clearer.

284.

In conclusion, we will mention a contrivance

by means of which our scientific readers may be

enabled to see these appearances distinctly at
one view, and even in their greatest splendour.
Cut in a piece of pasteboard five perfectly simi
lar square openings of about an inch, next each
other, exactly in a horizontal line : behind these

openings place five coloured glasses in the na

tural order, orange, yellow, green , blue, violet.
Let the series thus adjusted be fastened in an
opening of the camera obscura, so that the
bright sky may be seen through the squares,
or that the sun may shine on them ; they
will thus appear very powerfully coloured. Let
the spectator now examine them through the
prism , and observe the appearances , already
118 ACHROMATISM AND HYPERCHROMATISM .

familiar by the foregoing experiments, with

coloured objects, namely, the partly assisting,
partly neutralising effects of the edges and bor

ders , and the consequent apparent elongation or

reduction of the coloured squares with reference
to the horizontal line . The results witnessed by
the observer in this case, entirely correspond
with those in the cases before analysed ; we do
not, therefore, go through them again in detail ,
especially as we shall find frequent occasions
hereafter to return to the subject.- Note P.

XIX .

ACHROMATISM AND HYPERCHROMATISM.

285.

FORMERLY when much that is regular and con

stant in nature was considered as mere aber
ration and accident, the colours arising from re
fraction were but little attended to, and were

looked upon as an appearance attributable to

particular local circumstances .

286.

But after it had been assumed that this ap

pearance of colour accompanies refraction at all
times, it was natural that it should be considered
as intimately and exclusively connected with
that phenomenon ; the belief obtaining that the
 ACHROMATISM AND HYPERCHROMATISM. 119

measure of the coloured appearance was in pro

portion to the measure of the refraction , and

that they must advance pari passu with each

other.
287 .

If, again, philosophers ascribed the pheno

menon of a stronger or weaker refraction , not

indeed wholly, but in some degree, to the dif

ferent density of the medium, (as purer atmo
spheric air, air charged with vapours, water,
glass , according to their increasing density, in
crease the so-called refraction , or displacement
of the object ;) so they could hardly doubt that
the appearance of colour must increase in the

same proportion ; and hence took it for granted ,

in combining different mediums which were to
counteract refraction , that as long as refraction
existed, the appearance of colour must take
place, and that as soon as the colour disappeared,
the refraction also must cease.

288.

Afterwards it was, however, discovered that

this relation which was assumed to correspond,
was, in fact, dissimilar ; that two mediums can

refract an object with equal power, and yet pro

duce very dissimilar coloured borders .

289.

It was found that, in addition to the physical

principle to which refraction was ascribed , a
 I
120 ACHROMATISM AND HYPERCHROMATISM.

chemical one was also to be taken into the

account. We propose to pursue this subject

hereafter, in the chemical division of our in

quiry, and we shall have to describe the par

ticulars of this important discovery in our history
of the doctrine of colours . What follows may
suffice for the present.

290.

In mediums of similar or nearly similar re

fracting power, we find the remarkable circum
stance that a greater and lesser appearance of

colour can be produced by a chemical treat

ment ; the greater effect is owing, namely, to
acids , the lesser to alkalis . If metallic oxydes
are introduced into a common mass of glass , the

coloured appearance through such glasses be

comes greatly increased without any perceptible
change of refracting power. That the lesser

effect, again , is produced by alkalis , may be

easily supposed .
291 .

Those kinds of glass which were first em

ployed after the discovery, are called flint and

crown glass ; the first produces the stronger,

the second the fainter appearance of colour.

292.

We shall make use of both these denomina

tions as technical terms in our present statement,

 ACHROMATISM AND HYPERCHROMATISM . 121

and assume that the refractive power of both is

the same, but that flint-glass produces the
coloured appearance more strongly by one-third

than the crown-glass . The diagram (Plate 3 ,

fig. 2,) may serve in illustration.

293.

A black surface is here divided into com

partments for more convenient demonstration :

let the spectator imagine five white squares be

tween the parallel lines a, b, and c, d. The
square No. 1 , is presented to the naked eye un
moved from its place.

294.

But let the square No. 2, seen through a

crown-glass prism g, be supposed to be dis
placed by refraction three compartments, ex
hibiting the coloured borders to a certain extent ;
again, let the square No. 3, seen through a flint
glass prism h, in like manner be moved down
wards three compartments, when it will exhibit
the coloured borders by about a third wider
than No. 2.

295.

Again, let us suppose that the square No. 4,

has, like No. 2, been moved downwards three

compartments by a prism of crown -glass, and

that then by an oppositely placed prism h, of
122 ACHROMATISM AND HYPERCHROMATISM .

flint-glass, it has been again raised to its former

situation , where it now stands.

296 .

Here, it is true, the refraction is done away

with by the opposition of the two ; but as the
prism h, in displacing the square by refraction
through three compartments , produces coloured
borders wider by a third than those produced by
the prism g, so, notwithstanding the refraction
is neutralised, there must be an excess of
coloured border remaining. (The position of this
colour, as usual, depends on the direction of the
apparent motion (204) communicated to the

square by the prism h, and, consequently, it is

the reverse of the appearance in the two squares
2 and 3, which have been moved in an opposite
direction .) This excess of colour we have called
Hyperchromatism, and from this the achromatic
state may be immediately arrived at.

297.

For assuming that it was the square No. 5

which was removed three compartments from
its first supposed place, like No. 2, by a prism
of crown-glass g, it would only be necessary to
reduce the angle of a prism of flint-glass h, and
to connect it, reversed, to the prism g, in order
to raise the square No. 5 two degrees or com-
partments ; by which means the Hyperchro-
 ADVANTAGES OF SUBJECTIVE EXPERIMENTS . 123

matism of the first case would cease, the figure

would not quite return to its first position, and

yet be already colourless . The prolonged lines
of the united prisms, under No. 5 , show that a
single complete prism remains : again, we have
only to suppose the lines curved, and an object-
glass presents itself. Such is the principle of
the achromatic telescopes .

298 .

For these experiments, a small prism com-

posed of three different prisms, as prepared in
England, is extremely well adapted . It is to be
hoped our own opticians will in future enable
every friend of science to provide himself with
this necessary instrument.

XX .

ADVANTAGES OF SUBJECTIVE EXPERIMENTS .-TRANSITION

TO THE OBJECTIVE.

299.

We have presented the appearances of colour

as exhibited by refraction , first, by means of
subjective experiments ; and we have so far
arrived at a definite result, that we have been
enabled to deduce the phenomena in question
124 ADVANTAGES OF SUBJECTIVE EXPERIMENTS-

from the doctrine of semi-transparent mediums

and double images .

300.

In statements which have reference to nature,

everything depends on ocular inspection , and

these experiments are the more satisfactory as
they may be easily and conveniently made.
Every amateur can procure his apparatus with-
out much trouble or cost, and if he is a tolerable

adept in pasteboard contrivances , he may even

prepare a great part of his machinery himself.
A few plain surfaces, on which black , white,
grey, and coloured objects may be exhibited
alternately on a light and dark ground, are all
that is necessary. The spectator fixes them
before him, examines the appearances at the

edge of the figures conveniently, and as long as

he pleases ; he retires to a greater distance,
again approaches, and accurately observes the
progressive states of the phenomena.

301 .

Besides this, the appearances may be ob-

served with sufficient exactness through small

prisms, which need not be of the purest glass.

The other desirable requisites in these glass in-

struments will , however, be pointed out in the
section which treats of the apparatus . *

* This description of the apparatus was never given .

 OBJECTIVE EXPERIMENTS. 125

302.

A great advantage in these experiments , again,

is, that they can be made at any hour of the day
in any room , whatever aspect it may have. We
have no need to wait for sunshine, which in
general is not very propitious to northern ob-
servers.

OBJECTIVE EXPERIMENTS.

303.

THE objective experiments, on the contrary,

necessarily require the sun-light which, even
when it is to be had , may not always have the
most desirable relation with the apparatus
placed opposite to it . Sometimes the sun is
too high, sometimes too low, and withal only a
short time in the meridian of the best situated
room . It changes its direction during the ob-
servation , the observer is forced to alter his own
position and that of his apparatus, in conse-

quence of which the experiments in many cases

become uncertain . If the sun shines through

the prism it exhibits all inequalities , lines ,

and bubbles in the glass, and thus the appear-
ance is rendered confused, dim, and discoloured .

304 .

Yet both kinds of experiments must be inves-

tigated with equal accuracy. They appear to
126 OBJECTIVE EXPERIMENTS .

be opposed to each other, and yet are always

parallel . What one order of experiments exhi-
bits the other exhibits likewise, and yet each
has its peculiar capabilities, by means of which
certain effects of nature are made known to us
in more than one way.

305.

In the next place there are important pheno-

mena which may be exhibited by the union of
subjective and objective experiments. The

latter experiments again have this advantage,

that we can in most cases represent them by
diagrams, and present to view the component
relations of the phenomena. In proceeding,
therefore, to describe the objective experiments ,
we shall so arrange them that they may always
correspond with the analogous subjective exam-
ples ; for this reason , too, we annex to the num-
ber of each paragraph the number of the former
corresponding one. But we set out by ob-
serving generally that the reader must consult

the plates , that the scientific investigator must

be familiar with the apparatus in order that the
twin-phenomena in one mode or the other may
be placed before them .
 127

XXI.

REFRACTION WITHOUT THE APPEARANCE OF COLOUR.

306 ( 195, 196) .

THAT refraction may exhibit its effects without

producing an appearance of colour, is not to be
demonstrated so perfectly in objective as in sub-
jective experiments . We have, it is true , un-
limited spaces which we can look at through
the prism, and thus convince ourselves that no
colour appears where there is no boundary ; but

we have no unlimited source of light which we

can cause to act through the prism. Our light
comes to us from circumscribed bodies ; and

the sun, which chiefly produces our prismatic

appearances, is itself only a small, circum-
scribed, luminous object.

307.

We may, however, consider every larger open-

ing through which the sun shines , every larger
medium through which the sun -light is trans-
mitted and made to deviate from its course, as
so far unlimited that we can confine our atten-
tion to the centre of the surface without con-
sidering its boundaries.

308 (197).

If we place a large water- prism in the sun , a

128 CONDITIONS OF THE APPEARANCE OF COLOUR.

large bright space is refracted upwards by it on

the plane intended to receive the image, and the
middle of this illumined space will be colourless .
The same effect may be produced if we make
the experiment with glass prisms having angles
of few degrees : the appearance may be pro-
duced even through glass prisms, whose re-
fracting angle is sixty degrees, provided we
place the recipient surface near enough.

XXII.

CONDITIONS OF THE APPEARANCE OF COLOUR.

309 ( 198) .

ALTHOUGH, then, the illumined space before

mentioned appears indeed refracted and moved

from its place, but not coloured , yet on the hori-

zontal edges of this space we observe a coloured
appearance. That here again the colour is

solely owing to the displacement of a circum-

scribed object may require to be more fully
proved.
The luminous body which here acts is cir-
cumscribed : the sun, while it shines and diffuses
light, is still an insulated object. However

small the opening in the lid of a camera obscura

be made, still the whole image of the sun will
 CONDITIONS OF THE APPEARANCE OF COLOUR. 129

penetrate it. The light which streams from all

parts of the sun's disk, will cross itself in the

smallest opening, and form the angle which

corresponds with the sun's apparent diameter.
On the outside we have a cone narrowing to the

orifice ; within, this apex spreads again, produc

ing on an opposite surface a round image, which

still increases in size in proportion to the dis

tance of the recipient surface from the apex .
This image, together with all other objects of
the external landscape, appears reversed on the
white surface in question in a dark room.

310.
How little therefore we have here to do with

single sun-rays, bundles or fasces of rays , cylin

ders of rays, pencils, or whatever else of the kind
may be imagined, is strikingly evident. For the
convenience of certain diagrams the sun-light
may be assumed to arrive in parallel lines, but
it is known that this is only a fiction ; a fiction
quite allowable where the difference between
the assumption and the true appearance is un
important ; but we should take care not to suffer
such a postulate to be equivalent to a fact, and
proceed to further operations on such a fictitious
basis.

311.

Let the aperture in the window-shutter be

now enlarged at pleasure, let it be made round
K
130 CONDITIONS OF THE APPEARANCE OF COLOUR.

or square, nay, let the whole shutter be opened,

and let the sun shine into the room through the
whole window ; the space which the sun illu
mines will always be larger according to the
angle which its diameter makes ; and thus even
the whole space illumined by the sun through
the largest window is only the image of the sun
plus the size of the opening. We shall hereafter
have occasion to return to this.

312 ( 199).

If we transmit the image of the sun through

convex glasses we contract it towards the focus.

In this case, according to the laws before ex

plained , a yellow border and a yellow-red edge
must appear when the spectrum is thrown on
white paper.But as this experiment is dazzling
and inconvenient, it may be made more agree
ably with the image of the full moon. On con

tracting this orb by means of a convex glass, the

coloured edge appears in the greatest splendor ;
for the moon transmits a mitigated light in the
first instance, and can thus the more readily
produce colour which to a certain extent accom
panies the subduing of light : at the same time
the eye of the observer is only gently and agree
ably excited .

313 (200) .

If we transmit a luminous image through con

 CONDITIONS OF THE APPEARANCE OF COLOUR. 131

cave glasses, it is dilated . Here the image ap

pears edged with blue.

314.

The two opposite appearances may be pro

duced by a convex glass, simultaneously or in

succession ; simultaneously by fastening an
opaque disk in the centre of the convex glass ,
and then transmitting the sun's image. In this
case the luminous image and the black disk
within it are both contracted , and , consequently,
the opposite colours must appear. Again, we
can present this contrast in succession by first
contracting the luminous image towards the
focus, and then suffering it to expand again

beyond the focus, when it will immediately ex

hibit a blue edge.

315 ( 201 ) .

Here too what was observed in the subjective

experiments is again to be remarked , namely,

that blue and yellow appear in and upon the
white, and that both assume a reddish appear

ance in proportion as they mingle with the

black.

316 (202, 203) .

These elementary phenomena occur in all

subsequent objective experiments , as they con
stituted the groundwork of the subjective ones .
K 2
132 CONDITIONS OF THE APPEARANCE OF COLOUR.

The process too which takes place is the same ;

a light boundary is carried over a dark surface,
a dark surface is carried over a light boundary.

The edges must advance, and as it were push

over each other in these experiments as in the
former ones .

317 (204).

If we admit the sun's image through a larger

or smaller opening into the dark room , if we

transmit it through a prism so placed that its

refracting angle, as usual, is underneath ; the
luminous image, instead of proceeding in a

straight line to the floor, is refracted upwards

on a vertical surface placed to receive it. This
is the moment to take notice of the opposite
modes in which the subjective and objective re
fractions of the object appear.

318 .

If we look through a prism, held with its re

fracting angle underneath, at an object above

us, the object is moved downwards ; whereas a
luminous image refracted through the same

prism is moved upwards . This, which we here

merely mention as a matter of fact for the sake
of brevity, is easily explained by the laws of re
fraction and elevation .
 CONDITIONS OF THE APPEARANCE OF COLOUR. 133

319.

The luminous object being moved from its

place in this manner, the coloured borders ap
pear in the order, and according to the laws

before explained . The violet border is always

foremost, and thus in objective cases proceeds
upwards, in subjective cases downwards .

320 (205) .

The observer may convince himself in like

manner of the mode in which the appearance of

colour takes place in the diagonal direction

when the displacement is effected by means of
two prisms , as has been plainly enough shown
in the subjective example ; for this experiment,
however, prisms should be procured of few de
grees , say about fifteen.

321 (206, 207).

That the colouring of the image takes place

here too, according to the direction in which it

moves, will be apparent if we make a square

opening of moderate size in a shutter, and
cause the luminous image to pass through a
water- prism ; the spectrum being moved first in
the horizontal and vertical directions, then dia

gonally, the coloured edges will change their

position accordingly.
134 CONDITIONS OF THE APPEARANCE OF COLOUR.

322 (208) .

Whence it is again evident that to produce

colour the boundaries must be carried over each

other, not merely move side by side.

XXIII.

CONDITIONS OF THE INCREASE OF COLOUR.

323 (209) .

HERE too an increased displacement of the ob-

ject produces a greater appearance of colour.

324 (210) .

This increased displacement occurs,

1. By a more oblique direction of the im-

pinging luminous object through mediums with
parallel surfaces.

2. By changing the parallel form for one

more or less acute angled .
3. By increased proportion of the medium,
whether parallel or acute angled ; partly be-
cause the object is by this means more power-
fully displaced, partly because an effect depend-
ing on the mere mass co- operates .
4. By the distance of the recipient surface
from the refracting medium so that the coloured
 CONDITIONS OF THE INCREASE OF COLOUR. 135

spectrum emerging from the prism may be said

to have a longer way to travel .
5. When a chemical property produces its
effects under all these circumstances : this we

have already entered into more fully under the

head of achromatism and hyperchromatism .

325 (211).

The objective experiments have this advan-

tage that the progressive states of the pheno-
menon may be arrested and clearly represented
by diagrams, which is not the case with the

subjective experiments .

326.

We can observe the luminous image after it

has emerged from the prism, step by step, and
mark its increasing colour by receiving it on a

plane at different distances, thus exhibiting

before our eyes various sections of this cone,
with an elliptical base : again, the phenomenon
may at once be rendered beautifully visible

throughout its whole course in the following

manner :-Let a cloud of fine white dust be ex-
cited along the line in which the image passes

through the dark space ; the cloud is best pro-

duced by fine, perfectly dry, hair-powder. The
more or less coloured appearance will now be
painted on the white atoms , and presented in
136 CONDITIONS OF THE INCREASE OF COLOUR.

its whole length and breadth to the eye of the

spectator.

327.

By this means we have prepared some dia

grams , which will be found among the plates .

In these the appearance is exhibited from its
first origin, and by these the spectator can
clearly comprehend why the luminous image is
so much more powerfully coloured through
prisms than through parallel mediums .

328 (212).

At the two opposite outlines of the image an

opposite appearance presents itself, beginning
from an acute angle ;* the appearance spreads as

it proceeds further in space, according to this

angle. On one side, in the direction in which
the luminous image is moved, a violet border
advances on the dark , a narrower blue edge re

mains next the outline of the image. On the

opposite side a yellow border advances into the

light of the image itself, and a yellow-red edge

remains at the outline .

329 (213) .

Here, therefore, the movement of the dark

against the light, of the light against the dark,

may be clearly observed.

* Plate iv. fig. 1 .

 IV.
Fig 1.

08:

Fig2
 CONDITIONS OF THE INCREASE OF COLOUR. 137

330 (214) .

The centre of a large object remains long un-

coloured, especially with mediums of less den-
sity and smaller angles ; but at last the oppo-
site borders and edges touch each other, upon
which a green appears in the centre of the lu-
minous image.

331 (215) .

Objective experiments have been usually

made with the sun's image : an objective expe-

riment with a dark object has hitherto scarcely

been thought of. We have , however, prepared
a convenient contrivance for this also . Let the
large water-prism before alluded to be placed in
the sun , and let a round pasteboard disk be
fastened either inside or outside. The coloured
appearance will again take place at the outline,

beginning according to the usual law ; the edges

will appear, they will spread in the same pro-
portion, and when they meet, red will appear in
the centre . An intercepting square may be
added near the round disk, and placed in any
direction ad libitum , and the spectator can again
convince himself of what has been before so
often described .

332 (216) .

If we take away these dark objects from the

* Plate iv . fig. 2.
138 CONDITIONS OF THE INCREASE OF COLOUR.

prism, in which case, however, the glass is to be

carefully cleaned , and hold a rod or a large
pencil before the centre of the horizontal prism,
we shall then accomplish the complete immixture
of the violet border and the yellow-red edge,

and see only the three colours , the external

blue, and yellow, and the central red .

333 .

If again we cut a long horizontal opening in

the middle of a piece of pasteboard, fastened on
the prism , and then cause the sun- light to pass
through it, we shall accomplish the complete
union of the yellow border with the blue edge
upon the light, and only see yellow-red, green
and violet. The details of this are further

entered into in the description of the plates.

334 (217).

The prismatic appearance is thus by no

means complete and final when the luminous

image emerges from the prism. It is then only

that we perceive its elements in contrast ; for as
it increases these contrasting elements unite,
and are at last intimately joined . The section
of this phenomenon arrested on a plane surface
is different at every degree of distance from the
prism ; so that the notion of an immutable series

of colours, or of a pervading similar proportion

between them , cannot be a question for a
moment.
 EXPLANATION OF THE FOREGOING PHENOMENA. 139

XXIV.

EXPLANATION OF THE FOREGOING PHENOMENA.

335 (218).

As we have already entered into this analysis

circumstantially while treating of the subjective
experiments , as all that was of force there is

equally valid here, it will require no long de

tails in addition to show that the phenomena ,

which are entirely parallel in the two cases, may

also be traced precisely to the same sources.

336 (219).

That in objective experiments also we have

to do with circumscribed images, has been al
The sun may
ready demonstrated at large.
shine through the smallest opening, yet the

image of the whole disk penetrates beyond.

The largest prism may be placed in the open
sun-light, yet it is still the sun's image that is

bounded by the edges of the refracting surfaces,

and produces the accessory images of this bound
ary. We may fasten pasteboard, with many
openings cut in it, before the water- prism, yet
we still merely see multiplied images which,
after having been moved from their place by
refraction, exhibit coloured edges and borders,

and in these mere accessory images .

140 EXPLANATION OF THE FOREGOING PHENOMENA.

337 (235) .

In subjective experiments we have seen that

objects strongly relieved from each other pro
duce a very lively appearance of colour, and
this will be the case in objective experiments in
a much more vivid and splendid degree . The
sun's image is the most powerful brightness we
know ; hence its accessory image will be ener
getic in proportion , and notwithstanding its
really secondary dimmed and darkened charac
ter, must be still very brilliant. The colours
thrown by the sun-light through the prism on
any object, carry a powerful light with them,

for they have the highest and most intense

source of light, as it were , for their ground.

338.

That we are warranted in calling even these

accessory images semi- transparent, thus de
ducing the appearances from the doctrine of
the semi-transparent mediums, will be clear to

every one who has followed us thus far, but par

ticularly to those who have supplied themselves
with the necessary apparatus, so as to be en
abled at all times to witness the precision and
vivacity with which semi-transparent mediums
act.
 DECREASE OF THE APPEARANCE OF COLOUR. 141

XXV.

DECREASE OF THE APPEARANCE OF COLOUR.

339 ( 243 ) .

If we could afford to be concise in the descrip

tion of the decreasing coloured appearance in

subjective cases , we may here be permitted to

proceed with still greater brevity while we refer
to the former distinct statement. One circum

stance, only on account of its great importance,

may be here recommended to the reader's espe
cial attention as a leading point of our whole
thesis.

340 (244, 247) .

The decline of the prismatic appearance

must be preceded by its separation , by its reso

lution into its elements. At a due distance from

the prism, the image of the sun being entirely

coloured, the blue and yellow at length mix
completely, and we see only yellow-red, green ,
and blue-red . If we bring the recipient surface
nearer to the refracting medium, yellow and
blue appear again, and we see the five colours

with their gradations . At a still shorter dis

tance the yellow and blue separate from each
other entirely, the green vanishes, and the
image itself appears, colourless , between the

coloured edges and borders . The nearer we

bring the recipient surface to the prism, the
142 GREY OBJECTS.

narrower the edges and borders become, till at

last, when in contact with the prism , they are

reduced to nothing.

XXVI .

GREY OBJECTS.

341 (218) .

We have exhibited grey objects as very im

portant to our inquiry in the subjective experi

ments. They show, by the faintness of the
accessory images, that these same images are in

all cases derived from the principal object. If

we wish here, too, to carry on the objective ex
periments parallel with the others , we may con
veniently do this by placing a more or less dull
ground glass before the opening through which
the sun's image enters. By this means a sub
dued image would be produced , which on being
refracted would exhibit much duller colours on

the recipient plane than those immediately de

rived from the sun's disk ; and thus, even from
the intense sun -image, only a faint accessory

image would appear, proportioned to the mi

tigation of the light by the glass . This expe
riment, it is true, will only again and again
confirm what is already sufficiently familiar
to us.
 COLOURED OBJECTS. 143

XXVII.

COLOURED OBJECTS .

342 (260) .

THERE are various modes of producing coloured

images in objective experiments. In the first
place, we can fix coloured glass before the open-
ing, by which means a coloured image is at once
produced ; secondly, we can fill the water- prism
with coloured fluids ; thirdly, we can cause the

colours, already produced in their full vivacity

by the prism, to pass through proportionate
small openings in a tin plate, and thus prepare
small circumscribed colours for a second opera-
tion . This last mode is the most difficult ; for

owing to the continual progress of the sun , the

image cannot be arrested in any direction at
will. The second method has also its incon-

veniences, since not all coloured liquids can

be prepared perfectly bright and clear. On
these accounts the first is to be preferred, and
deserves the more to be adopted because natural
philosophers have hitherto chosen to consider
the colours produced from the sun-light through

the prism, those produced through liquids and

glasses, and those which are already fixed on
paper or cloth, as exhibiting effects equally to
be depended on, and equally available in de-
monstration .

343.

As it is thus merely necessary that the image

144 COLOURED OBJECTS.

should be coloured , so the large water-prism

before alluded to affords us the best means of

effecting this . A pasteboard screen may be

contrived to slide before the large surfaces of
the prism, through which, in the first instance,
the light passes uncoloured . In this screen

openings of various forms may be cut, in order

to produce different images, and consequently

different accessory images. This being done,
we need only fix coloured glasses before the
openings , in order to observe what effect refrac

tion produces on coloured images in an objective

sense.

344 .

A series of glasses may be prepared in a

mode similar to that before described ( 284) ;
these should be accurately contrived to slide in
the grooves of the large water- prism . Let the
sun then shine through them , and the coloured

images refracted upwards will appear bordered

and edged, and will vary accordingly for
these borders and edges will be exhibited quite
distinctly on some images, and on others will

be mixed with the specific colour of the glass,

which they will either enhance or neutralize .
Every observer will be enabled to convince
himself here again that we have only to do with
the same simple phenomenon so circumstan

tially described subjectively and objectively.

 ACHROMATISM AND HYPERCHROMATISM . 145

XXVIII .

ACHROMATISM AND HYPERCHROMATISM .

345 (285, 290) .

It is possible to make the hyperchromatic and

achromatic experiments objectively as well as
subjectively . After what has been already
stated, a short description of the method will
suffice, especially as we take it for granted that
the compound prism before mentioned is in the
hands of the observer.

346 .

Let the sun's image pass through an acute-

angled prism of few degrees , prepared from
crown-glass , so that the spectrum be refracted
upwards on an opposite surface ; the edges will
appear coloured, according to the constant law,
namely, the violet and blue above and outside,
the yellow and yellow-red below and within the
image. As the refracting angle of this prism is
undermost, let another proportionate prism of
flint-glass be placed against it, with its refracting
angle uppermost. The sun's image will by this
means be again moved to its place, where, owing
to the excess of the colouring power of the
prism of flint-glass , it will still appear a little
coloured, and, in consequence of the direction
in which it has been moved, the blue and violet
L
146 ACHROMATISM AND HYPERCHROMATISM .

will now appear underneath and outside, the

yellow and yellow-red above and inside.

347.

If the whole image be now moved a little up-

wards by a proportionate prism of crown-glass ,

the hyperchromatism will disappear, the sun's
image will be moved from its place , and yet
will appear colourless .

348 .

With an achromatic object-glass composed of

three glasses, this experiment may be made
step by step, if we do not mind taking out the
glasses from their setting . The two convex
glasses of crown-glass in contracting the sun's
image towards the focus, the concave glass of
flint-glass in dilating the image beyond it, éx-
hibit at the edges the usual colours . A convex
glass united with a concave one exhibits the
colours according to the law of the latter. If
all three glasses are placed together, whether
we contract the sun's image towards the focus,
or suffer it to dilate beyond the focus, coloured
'
edges never appear, and the achromatic effect
intended by the optician is, in this case, again
attained.

349.

But as the crown-glass has always a greenish

tint, and as a tendency to this hue may be more
 ACHROMATISM AND HYPERCHROMATISM. 147

decided in large and strong object-glasses,

and under certain circumstances produce the

compensatory red, (which, however, in repeated

experiments with several instruments of this
kind did not occur to us, ) philosophers have
resorted to the most extraordinary modes of
explaining such a result ; and having been com-
pelled, in support of their system, theoretically
to prove the impossibility of achromatic tele-
scopes, have felt a kind of satisfaction in having
some apparent ground for denying so great an
improvement. Of this, however, we can only
treat circumstantially in our historical account
of these discoveries .

XXIX .

COMBINATION OF SUBJECTIVE AND OBJECTIVE

EXPERIMENTS .

350.

HAVING shown above ( 318 ) that refraction , con-

sidered objectively and subjectively, must act in
opposite directions, it will follow that if we com-

bine the experiments, the effects will recipro-

cally destroy each other.

351 .

Let the sun's image be thrown upwards on a

L 2
148 COMBINATION OF SUBJECTIVE

vertical plane, through a horizontally- placed

prism . If the prism is long enough to admit of
the spectator also looking through it, he will see
the image elevated by the objective refraction
again depressed , and in the same place in which
it appeared without refraction.

352.

Here a remarkable case presents itself, but

at the same time a natural result of a general
law. For since, as often before stated, the ob
jective sun's image thrown on the vertical

plane is not an ultimate or unchangeable state

of the phenomenon , so in the above operation
the image is not only depressed when seen
through the prism, but its edges and borders
are entirely robbed of their hues, and the
spectrum is reduced to a colourless circular
form .

353.

By employing two perfectly similar prisms

placed next each other , for this experiment, we
can transmit the sun's image through one, and
look through the other.

354 .

If the spectator advances nearer with the

prism through which he looks, the image is
again elevated , and by degrees becomes coloured
according to the law of the first prism. If he
 AND OBJECTIVE EXPERIMENTS. 149

again retires till he has brought the image to the

neutralized point, and then retires still farther

away, the image, which had become round and
colourless , moves still more downwards and be-

comes coloured in the opposite sense, so that if

we look through the prism and upon the re-
fracted spectrum at the same time, we see the
same image coloured according to subjective and
objective laws.

355.

The modes in which this experiment may be

varied are obvious . If the refracting angle of

the prism, through which the sun's image was

objectively elevated , is greater than that of the
prism through which the observer looks, he
must retire to a much greater distance, in order
to depress the coloured image so low on the
vertical plane that it shall appear colourless ,
and vice versa.

356.

It will be easily seen that we may exhibit

achromatic and hyperchromatic effects in a
similar manner, and we leave it to the amateur

to follow out such researches more fully. Other

complicated experiments in which prisms and

lenses are employed together, others again, in

which objective and subjective experiments are
variously intermixed, we reserve for a future
150 TRANSITION.

occasion, when it will be our object to trace such

effects to the simple phenomena with which we
are now sufficiently familiar.

XXX.

TRANSITION.

357.

In looking back on the description and analysis

of dioptrical colours , we do not repent either
that we have treated them so circumstantially,
or that we have taken them into consideration

before the other physical colours, out of the

order we ourselves laid down. Yet, before we

quit this branch of our inquiry, it may be as

well to state the reasons that have weighed
with us .

358 .

If some apology is necessary for having

treated the theory of the dioptrical colours, par-

ticularly those of the second class , so diffusely,

we should observe, that the exposition of any
branch of knowledge is to be considered partly
with reference to the intrinsic importance of the

subject, and partly with reference to the par-

ticular necessities of the time in which the
 TRANSITION. 151

inquiry is undertaken . In our own case we

were forced to keep both these considerations

constantly in view. In the first place we

had to state a mass of experiments with our

consequent convictions ; next, it was our

especial aim to exhibit certain phenomena

(known, it is true, but misunderstood , and above
all, exhibited in false connection, ) in that na

tural and progressive development which is

strictly and truly conformable to observation ;
in order that hereafter, in our polemical or his
torical investigations , we might be enabled to
bring a complete preparatory analysis to bear
on, and elucidate, our general view. The details
we have entered into were on this account

unavoidable ; they may be considered as a re

luctant consequence of the occasion . Hereafter,
when philosophers will look upon a simple
principle as simple, a combined effect as

combined ; when they will acknowledge the

first elementary, and the second complicated
states, for what they are ; then , indeed, all this

statement may be abridged to a narrower form ;

a labour which , should we ourselves not be able
to accomplish it, we bequeath to the active in

terest of contemporaries and posterity.

359.

With respect to the order of the chapters, it

should be remembered that natural phenomena ,
 152 TRANSITION.

which are even allied to each other, are not con

nected in any particular sequence or constant

series ; their efficient causes act in a narrow
circle, so that it is in some sort indifferent what

phenomenon is first or last considered ; the main

point is, that all should be as far as possible

present to us, in order that we may embrace
them at last from one point of view, partly ac

cording to their nature, partly according to

generally received methods.

360.

Yet, in the present particular instance, it may

be asserted that the dioptrical colours are justly
placed at the head of the physical colours ; not
only on account of their striking splendour and
their importance in other respects, but because,
in tracing these to their source , much was ne
cessarily entered into which will assist our sub
sequent enquiries.

361 .

For, hitherto, light has been considered as a

kind of abstract principle, existing and acting
independently ; to a certain extent self- modified ,
and on the slightest cause, producing colours
out of itself. To divert the votaries of physical
science from this mode of viewing the subject ;

to make them attentive to the fact, that in pris

matic and other appearances we have not to do
 TRANSITION . 153

with light as an uncircumscribed and modify-

ing principle, but as circumscribed and modi-
fied ; that we have to do with a luminous image ;
with images or circumscribed objects generally,
whether light or dark : this was the purpose we

had in view, and such is the problem to be solved.

362.

All that takes place in dioptrical cases, -

especially those of the second class which are

connected with the phenomena of refraction, -is
now sufficiently familiar to us, and will serve
as an introduction to what follows.

363 .

Catoptrical appearances remind us of the

physiological phenomena, but as we ascribe a

more objective character to the former, we

thought ourselves justified in classing them
with the physical examples. It is of import-
ance, however, to remember that here again it
is not light, in an abstract sense, but a luminous
image that we have to consider.

364.

In proceeding onwards to the paroptrical

class, the reader, if duly acquainted with the

foregoing facts, will be pleased to find himself
once more in the region of circumscribed forms.
The shadows of bodies, especially, as secondary
154 CATOPTRICAL COLOURS .

images , so exactly accompanying the object,

will serve greatly to elucidate analogous ap-
pearances .

365.

We will not, however, anticipate these state-

ments, but proceed as heretofore in what we
consider the regular course.

XXXI .

CATOPTRICAL COLOURS .

366 .

CATOPTRICAL Colours are such as appear in con-

sequence of a mirror-like reflection . We as-

sume, in the first place, that the light itself, as

well as the surface from which it is reflected, is

perfectly colourless . In this sense the appear-

ances in question come under the head of phy-
sical colours . They arise in consequence of

reflection, as we found the dioptrical colours of

the second class appear by means of refraction .
Without further general definitions, we turn our

attention at once to particular cases , and to the

conditions which are essential to the exhibition

of these phenomena .
 CATOPTRICAL COLOURS . 155

367 .

If we unroll a coil of bright steel -wire, and

after suffering it to spring confusedly together

again, place it at a window in the light, we shall
see the prominent parts of the circles and con-
volutions illumined, but neither resplendent
nor iridescent. But if the sun shines on the

wire , this light will be condensed into a point,

and we perceive a small resplendent image of
the sun, which, when seen near, exhibits no

colour . On retiring a little, however, and fixing

the eyes on this refulgent appearance, we dis-
cern several small mirrored suns, coloured in the

most varied manner ; and although the impres-

sion is that green and red predominate, yet, on
a more accurate inspection , we find that the
other colours are also present.

368 .

If we take an eye-glass, and examine the ap-

pearance through it, we find the colours have

vanished, as well as the radiating splendour in

which they were seen, and we perceive only the

small luminous points, the repeated images of
the sun. We thus find that the impression is

subjective in its nature, and that the appear-

ance is allied to those which we have adverted

to under the name of radiating halos ( 100) .

 156 CATOPTRICAL COLOURS .

369.

We can, however, exhibit this phenomenon

objectively. Let a piece of white paper be fast

ened beneath a small aperture in the lid of a
camera-obscura, and when the sun shines

through this aperture, let the confusedly-rolled

steel -wire be held in the light, so that it be op

posite to the paper. The sun -light will impinge

on and in the circles of the wire, and will not,
as in the concentrating lens of the eye, display

itself in a point ; but, as the paper can receive

the reflection of the light in every part of its
surface will be seen in hair- like lines , which are
also iridescent.

370.

This experiment is purely catoptrical ; for as

we cannot imagine that the light penetrates the
surface of the steel, and thus undergoes a
change, we are soon convinced that we have

here a mere reflection which, in its subjective

character, is connected with the theory of faintly
acting lights, and the after-image of dazzling
lights , and as far as it can be considered ob

jective, announces even in the minutest appear

ances, a real effect, independent of the action
and reaction of the eye.

371 .

We have seen that to produce these effects

 CATOPTRICAL COLOURS . 157

not merely light but a powerful light is neces

sary ; that this powerful light again is not an
abstract and general quality , but a circumscribed
light, a luminous image. We can convince our
selves still further of this by analogous cases .

372 .

A polished surface of silver placed in the sun

reflects a dazzling light, but in this case no
colour is seen. If, however, we slightly scratch
the surface, an iridescent appearance, in which
green and red are conspicuous , will be exhibited

at a certain angle. In chased and carved

metals the effect is striking : yet it may be re
marked throughout that, in order to its appear
ance, some form, some alternation of light and

dark must co- operate with the reflection ; thus

a window-bar, the stem of a tree, an accident

ally or purposely interposed object produces a

perceptible effect. This appearance, too, may
be exhibited objectively in the camera-obscura .

373.

If we cause a polished plated surface to be so

acted on by aqua fortis that the copper within is
touched, and the surface itself thus rendered
rough, and if the sun's image be then reflected
from it, the splendour will be reverberated from
every minutest prominence, and the surface will
appear iridescent. So, if we hold a sheet of
158 CATOPTRICAL COLOURS .

black unglazed paper in the sun , and look at it.

attentively, it will be seen to glisten in its mi
nutest points with the most vivid colours.

374 .

All these examples are referable to the same

conditions . In the first case the luminous

image is reflected from a thin line ; in the

second probably from sharp edges ; in the third
from very small points . In all a very powerful
and circumscribed light is requisite . For all
these appearances of colour again it is necessary

that the eye should be at a due distance from

the reflecting points .
1 112
375.

If these observations are made with the mi

croscope, the appearance will be greatly in

creased in force and splendour, for we then see
the smallest portion of the surfaces, lit by the
sun, glittering in these colours of reflection,
which, allied to the hues of refraction , now
attain their highest degree of brilliancy. In
such cases we may observe a vermiform iri
descence on the surface of organic bodies, the
further description of which will be given here,
after.

376 .

Lastly, the colours which are chiefly exhi

 CATOPTRICAL COLOURS. 159

bited in reflection are red and green, whence

we may infer that the linear appearance espe-

cially consists of a thin line of red , bounded by
blue on one side and yellow on the other. If
these triple lines approach very near together,
the intermediate space must appear green ; a

phenomenon which will often occur to us as we

proceed .

377.

We frequently meet with these colours in

nature. The colours of the spider's web might

be considered exactly of the same class with
those reflected from the steel wire, except that

the non-translucent quality of the former is not

so certain as in the case of steel ; on which ac-
count some have been inclined to class the

colours of the spider's web with the phenomena

of refraction .

378. I

In mother-of- pearl we perceive infinitely fine

organic fibres and lamellæ in juxta- position ,
from which, as from the scratched silver before

alluded to , varied colours, but especially red and

green, may arise.

379 .

The changing colours of the plumage of birds

may also be mentioned here, although in all or-
160 CATOPTRICAL COLOURS .

ganic instances a chemical principle and an

adaptation of the colour to the structure may be
assumed ; considerations to which we shall re-
turn in treating of chemical colours.

380.

That the appearances of objective halos also

approximate catoptrical phenomena will be

readily admitted, while we again do not deny

that refraction as well may here come into

the account. For the present we restrict our-

selves to one or two observations ; hereafter we

may be enabled to make a fuller application of

general principles to particular examples .

381 .

We first call to mind the yellow and red

circles produced on a white or grey wall by a
light placed near it (88). Light when reflected
appears subdued, and a subdued light excites

the impression of yellow, and subsequently of

red .

382.

Let the wall be illumined by a candle placed

quite close to it. The farther the light is dif-
fused the fainter it becomes ; but it is still the
effect of the flame, the continuation of its
action, the dilated effect of its image. We
might, therefore, very fairly call these circles
 CATOPTRICAL COLOURS . 161

reiterated images, because they constitute the

successive boundaries of the action of the light,
and yet at the same time only present an ex
tended image of the flame.

383.

If the sky is white and luminous round the

sun owing to the atmosphere being filled with
light vapours ; if mists or clouds pass be
fore the moon, the reflection of the disk mir

rors itself in them ; the halos we then perceive

are single or double , smaller or greater, some
times very large, often colourless , sometimes
coloured .

384.

I witnessed a very beautiful halo round the

moon the 15th of November, 1799 , when the
barometer stood high ; the sky was cloudy and
vapoury. The halo was completely coloured ,
and the circles were concentric round the light
as in subjective halos . That this halo was ob
jective I was presently convinced by covering
the moon's disk , when the same circles were

nevertheless perfectly visible .

385.

The different extent of the halos appears to

have a relation with the proximity or distance

of the vapour from the eye of the observer.
M
162 CATOPTRICAL COLOURS .

386 .

As window- panes lightly breathed upon in-

crease the brilliancy of subjective halos , and in
some degree give them an objective character,
so, perhaps, with a simple contrivance in winter,
during a quickly freezing temperature, a more
exact definition of this might be arrived at.

387.

How much reason we have in considering

these circles to insist on the image and its
effects, is apparent in the phenomenon of the
so-called double suns . Similar double images

always occur in certain points of halos and

circles, and only present in a circumscribed
form what takes place in a more general way in
the whole circle . All this will be more conve-

niently treated in connexion with the appear-

ance of the rainbow.- Note Q.

388 .

In conclusion it is only necessary to point out

the affinity between the catoptrical and parop-
tical colours .

We call those paroptical colours which ap-

pear when the light passes by the edge of an
opaque colourless body. How nearly these are
allied to the dioptrical colours of the second
class will be easily seen by those who are con-
vinced with us that the colours of refraction
 CATOPTRICAL COLOURS . 163

take place only at the edges of objects . The

affinity again between the catoptrical and par-

optical colours will be evident in the following

chapter.

XXXII.

PAROPTICAL COLOURS .

389.

THE paroptical colours have been hitherto called

peri-optical, because a peculiar effect of light
was supposed to take place as it were round the

object, and was ascribed to a certain flexibility

of the light to and from the object.

390.

These colours again may be divided into sub-

jective and objective, because they appear
partly without us, as it were, painted on sur-
faces, and partly within us, immediately on the
retina. In this chapter we shall find it more to
our purpose to take the objective cases first,
since the subjective are so closely connected
with other appearances already known to us ,
that it is hardly possible to separate them .

391 .

The paroptical colours then are so called be-

M 2
164 PAROPTICAL COLOURS .

cause the light must pass by an outline or edge

to produce them . They do not, however, always
appear in this case ; to produce the effect very
particular conditions are necessary besides .

392.

It is also to be observed that in this instance

again light does not act as an abstract diffusion
(361 ), the sun shines towards an edge . The
volume of light poured from the sun-image
passes by the edge of a substance, and occasions
shadows. Within these shadows we shall pre
sently find colours appear.

393.

But, above all , we should make the experi

ments and observations that bear upon our pre

sent inquiry in the fullest light. We , there

fore, place the observer in the open air before
we conduct him to the limits of a dark room.

394.

A person walking in sun - shine in a garden , or

on any level path, may observe that his shadow
only appears sharply defined next the foot on
which he rests ; farther from this point, espe

cially round the head, it melts away into the

bright ground . For as the sun-light proceeds
not only from the middle of the sun, but also
acts cross-wise from the two extremes of every
 PAROPTICAL COLOURS . 165

diameter, an objective parallax takes place

which produces a half- shadow on both sides of
the object.

395.

If the person walking raises and spreads his

hand, he distinctly sees in the shadow of each
finger the diverging separation of the two half
shadows outwards, and the diminution of the

principal shadow inwards, both being effects of

the cross action of the light.

396 .

This experiment may be repeated and varied

before a smooth wall, with rods of different
thicknesses , and again with balls ; we shall

always find that the farther the object is re

moved from the surface of the wall , the more

the weak double shadow spreads, and the more

the forcible main shadow diminishes, till at last

the main shadow appears quite effaced, and

even the double shadows become so faint, that
they almost disappear ; at a still greater dis
tance they are, in fact, imperceptible.

397.

That this is caused by the cross- action of the

light we may easily convince ourselves ; for the

shadow of a pointed object plainly exhibits two

points. We must thus never lose sight of the
166 PAROPTICAL COLOURS .

fact that in this case the whole sun-image acts ,

produces shadows, changes them to double

shadows, and finally obliterates them.

398.

Instead of solid bodies let us now take open

ings cut of various given sizes next each other,

and let the sun shine through them on a plane
surface at some little distance ; we shall find
that the bright image produced by the sun on
the surface, is larger than the opening ; this is
because one edge of the sun shines towards the
opposite edge of the opening, while the other
edge of the disk is excluded on that side.
Hence the bright image is more weakly lighted
towards the edges .

399.

If we take square openings of any size we

please, we shall find that the bright image on a

surface nine feet from the opening, is on every

side about an inch larger than the opening ;

thus nearly corresponding with the angle of the
apparent diameter of the sun .

400.

That the brightness should gradually diminish

towards the edges of the image is quite natural,

for at last only a minimum of the light can act

cross-wise from the sun's circumference through
the edge of the aperture .
 PAROPTICAL COLOURS . 167

401 .

Thus we here again see how much reason we

have in actual observation to guard against the
assumption of parallel rays , bundles and fasces
of rays, and the like hypothetical notions .

402.

We might rather consider the splendour of

the sun, or of any light, as an infinite specular
multiplication of the circumscribed luminous

image, whence it may be explained that all

square openings through which the sun shines,
at certain distances, according as the apertures
are greater or smaller, must give a round image
of light .

403.

The above experiments may be repeated

through openings of various shapes and sizes,

and the same effect will always take place at

proportionate distances . In all these cases , how-

ever, we may still observe that in a full light
and while the sun merely shines past an edge,
no colour is apparent .

404 .

We therefore proceed to experiments with a

subdued light, which is essential to the appear-

ance of colour. Let a small opening be made in

the window-shutter of a dark room ; let the
168 PAROPTICAL COLOURS .

crossing sun- light which enters , be received on

a surface of white paper, and we shall find that

the smaller the opening is, the dimmer the light
image will be. This is quite obvious, because
the paper does not receive light from the whole

sun, but partially from single points of its disk .

405 .

If we look attentively at this dim image of

the sun, we find it still dimmer towards the out-

lines where a yellow border is perceptible . The

colour is still more apparent if a vapour or a

transparent cloud passes before the sun , thus

subduing and dimming its brightness . The

halo on the wall , the effect of the decreasing

brightness of a light placed near it, is here
forced on our recollection . (88. )

406 .

If we examine the image more accurately , we

perceive that this yellow border is not the only

appearance of colour ; we can see, besides, a
bluish circle, if not even a halo-like repetition
of the coloured border. If the room is quite
dark, we discern that the sky next the sun also
has its effect we see the blue sky, nay, even

the whole landscape, on the paper, and are thus

again convinced that as far as regards the
sun, we have here only to do with a luminous
image.
 PAROPTICAL COLOURS . 169

407.

If we take a somewhat larger square opening,

so large that the image of the sun shining

through it does not immediately become round ,
we may distinctly observe the half- shadows of

every edge or side, the junction of these in the

corners, and their colours ; just as in the above-
mentioned appearance with the round opening.

408.

We have now subdued a parallactic light

by causing it to shine through small apertures,
but we have not taken from it its parallactic

character ; so that it can produce double shadows

of bodies , although with diminished power.
These double shadows which we have hitherto

been describing, follow each other in light and

dark, coloured and colourless circles, and pro-

duce repeated, nay, almost innumerable halos.

These effects have been often represented in
drawings and engravings . By placing needles ,
hairs, and other small bodies, in the subdued
light, the numerous halo- like double shadows

may be increased ; thus observed , they have

been ascribed to an alternating flexile action
of the light, and the same assumption has been
employed to explain the obliteration of the
central shadow, and the appearance of a light
in the place of the dark.
170 PAROPTICAL COLOURS .

409.

For ourselves , we maintain that these again

are parallactic double shadows, which appear
edged with coloured borders and halos .

410.

After having seen and investigated the fore

going phenomena, we can proceed to the ex
periments with knife-blades, * exhibiting effects
which may be referred to the contact and paral
lactic mutual intersection of the half-shadows

and halos already familiar to us.

411 .

Lastly, the observer may follow out the ex

periments with hairs , needles, and wires , in the
half-light produced as before described by the
sun, as well as in that derived from the blue

sky, and indicated on the white paper. He will

thus make himself still better acquainted with
the true nature of this phenomenon .

412.

But since in these experiments everything

depends on our being persuaded of the paral

lactic action of the light, we can make this
more evident by means of two sources of light,
the two shadows from which intersect each

other, and may be altogether separated. By

day this may be contrived with two small

* See Newton's Optics, book iii.

 PAROPTICAL COLOURS . 171

openings in a window- shutter ; by night, with

two candles . There are even accidental effects

in interiors, on opening and closing shutters, by

means of which we can better observe these ap
pearances than with the most careful apparatus.
But still , all and each of these may be reduced
to experiment by preparing a box which the
observer can look into from above, and gradually

diminishing the openings after having caused a

double light to shine in . In this case, as might
be expected, the coloured shadow, considered
under the physiological colours, appears very
easily.

413.

It is necessary to remember, generally, what

has been before stated with regard to the nature
of double shadows, half-lights, and the like.
Experiments also should especially be made
with different shades of grey placed next each
other, where every stripe will appear light by a
darker, and dark by a lighter stripe next it. If
at night, with three or more lights , we produce
shadows which cross each other successively,

we can observe this phenomenon very distinctly ,

and we shall be convinced that the physiological

case before more fully treated , here comes into

the account (38 ) .

414 .

To what extent the appearances that accom

172 PAROPTICAL COLOURS.

pany the paroptical colours, may be derived

from the doctrine of subdued lights , from half
shadows, and from the physiological disposition
of the retina, or whether we shall be forced to
take refuge in certain intrinsic qualities of light,
as has hitherto been done, time may teach .
Suffice it here to have pointed out the con
ditions under which the paroptical colours ap
pear, and we may hope that our allusion to
their connexion with the facts before adduced

by us will not remain unnoticed by the ob

servers of nature.

415 .

The affinity of the paroptical colours with the

dioptrical of the second class will also be readily
seen and followed up by every reflecting inves
tigator. Here, as in those instances, we have
to do with edges or boundaries ; here, as in
those instances , with a light, which appears at
the outline . How natural, therefore, it is to
conclude that the paroptical effects may be
heightened, strengthened, and enriched by the
dioptrical. Since, however, the luminous image
actually shines through the medium , we can
here only have to do with objective cases of re
fraction it is these which are strictly allied to
the paroptical cases. The subjective cases of
refraction , where we see objects through the
medium , are quite distinct from the paroptical .
 PAROPTICAL COLOURS . 173

We have already recommended them on ac

count of their clearness and simplicity.

416 .

The connexion between the paroptical colours

and the catoptrical may be already inferred

from what has been said : for as the catoptrical
colours only appear on scratches, points , steel
wire, and delicate threads, so it is nearly the

same case as if the light shone past an edge.

The light must always be reflected from an
edge in order to produce colour. Here again ,
as before pointed out, the partial action of the
luminous image and the subduing of the light
are both to be taken into the account.

417 .

We add but few observations on the subjective

paroptical colours, because these may be classed

partly with the physiological colours , partly

with the dioptrical of the second order. The
greater part hardly seem to belong here, but,
when attentively considered, they still diffuse a
satisfactory light over the whole doctrine, and
establish its connexion .

418 .

If we hold a ruler before the eyes so that the

flame of a light just appears above it, we see
the ruler as it were indented and notched at the
174 PAROPTICAL COLOURS .

place where the light appears . This seems de

ducible from the expansive power of light acting
on the retina ( 18) .

419 .

The same phenomenon on a large scale is ex

hibited at sun-rise ; for when the orb appears

distinctly, but not too powerfully, so that we can

still look at it, it always makes a sharp indent
ation in the horizon.

420 .

If, when the sky is grey, we approach a win

dow, so that the dark cross of the window-bars
be relieved on the sky ; if after fixing the eyes
on the horizontal bar we bend the head a little
forward ; on half closing the eyes as we look up,

we shall presently perceive a bright yellow- red

border under the bar, and a bright light-blue
one above it. The duller and more monotonous
the grey of the sky, the more dusky the room,

and, consequently, the more previously unex

cited the eye, the livelier the appearance will
be ; but it may be seen by an attentive observer
even in bright daylight.

421 .

If we move the head backwards while half

closing the eyes, so that the horizontal bar be

seen below, the phenomenon will appear re
 PAROPTICAL COLOURS . 175

versed. The upper edge will appear yellow,

the under edge blue.

422.

Such observations are best made in a dark

room . If white paper is spread before the

opening where the solar microscope is com-

monly fastened , the lower edge of the circle
will appear blue, the upper yellow, even while
the eyes are quite open , or only by half- closing
them so far that a halo no longer appears round
the white . Ifthe head is moved backwards the
colours are reversed .

423 .

These phenomena seem to prove that the hu-

mours of the eye are in fact only really achro-
matic in the centre where vision takes place,
but that towards the circumference, and in un-

usual motions of the eyes, as in looking hori-

zontally when the head is bent backwards or
forwards, a chromatic tendency remains , espe-

cially when distinctly relieved objects are thus

looked at . Hence such phenomena may be

considered as allied to the dioptrical colours of

the second class .

424 .

Similar colours appear if we look on black

and white objects, through a pin-hole in a card.
176 PAROPTICAL COLOURS .

Instead of a white object we may take the mi-

nute light aperture in the tin plate of a camera

obscura, as prepared for paroptical experi-
ments .

425 .

If we look through a tube, the farther end of

which is contracted or variously indented , the
same colours appear .

426 .

The following phenomena appear to me to be

more nearly allied to the paroptical appear-
ances. If we hold up a needle near the eye,

the point appears double. A particularly re-

markable effect again is produced if we look

towards a grey sky through the blades of knives

prepared for paroptical experiments . We seem
to look through a gauze ; a multitude of threads

appear to the eye ; these are in fact only the

reiterated images of the sharp edges, each of
which is successively modified by the next, or

perhaps modified in a parallactic sense by the

oppositely acting one, the whole mass being
thus changed to a thread-like appearance.

427 .

Lastly, it is to be remarked that if we look

through the blades towards a minute light in
 PAROPTICAL COLOURS . 177

the window-shutter, coloured stripes and halos

appear on the retina as on the paper.

428.

The present chapter may be here terminated,

the less reluctantly, as a friend has undertaken
to investigate this subject by further experi
ments . In our recapitulation , in the descrip
tion of the plates and apparatus, we hope here
after to give an account of his observations . *

XXXIII .

EPOPTICAL COLOURS .

429 .

We have hitherto had to do with colours which

appear with vivacity, but which immediately

vanish again when certain conditions cease .
We have now to become acquainted with others,
which it is true are still to be considered as
transient, but which, under certain circum
stances, become so fixed that, even after the
conditions which first occasioned their appear
ance cease, they still remain , and thus con

* The observations here alluded to never appeared .

N
178 EPOPTICAL COLOURS.

stitute the link between the physical and the

chemical colours .

430.

They appear from various causes on the sur-

face of a colourless body, originally, without

communication , die or immersion ( Bag ) ; and
we now proceed to trace them, from their faint-
est indication to their most permanent state ,

through the different conditions of their appear-

ance, which for easier survey we here at once

summarily state.

431 .

First condition . -The contact of two smooth

surfaces of hard transparent bodies .

First case if masses or plates of glass, or if
lenses are pressed against each other.
Second case : if a crack takes place in a

solid mass of glass , chrystal, or ice.

Third case if lamellæ of transparent stones
become separated .
Second condition .-If a surface of glass or a

polished stone is breathed upon .

Third condition .-The combination of the

two last ; first, breathing on the glass , then

placing another plate of glass upon it, thus ex-
citing the colours by pressure ; then removing
the upper glass, upon which the colours begin
to fade and vanish with the breath .
 EPOPTICAL COLOURS . 179

Fourth condition .-Bubbles of various liquids ,

soap, chocolate, beer, wine, fine glass bubbles .
Fifth condition . -Very fine pellicles and la

mellæ, produced by the decomposition of mine

rals and metals . The pellicles of lime, the sur
face of stagnant water, especially if impregnated
with iron, and again pellicles of oil on water,
especially of varnish on aqua fortis .
Sixth condition . - If metals are heated ; the
operation of imparting tints to steel and other
metals .

Seventh condition . - If the surface of glass is

beginning to decompose.

432.

First condition , first case. If two convex

glasses, or a convex and plane glass , or, best of

all , a convex and concave glass come in contact,
concentric coloured circles appear. The pheno

menon exhibits itself immediately on the slight

est pressure, and may then be gradually carried
through various successive states . We will de

scribe the complete appearance at once, as we

shall then be better enabled to follow the differ

ent states through which it passes .

433 .

The centre is colourless ; where the glasses

are, so to speak, united in one by the strongest
pressure, a dark grey point appears with a silver
N2
180 EPOPTICAL COLOURS .

white space round it : then follow, in decreasing

distances , various insulated rings, all consisting
of three colours , which are in immediate con
tact with each other. Each of these rings , of

which perhaps three or four might be counted,

is yellow on the inner side, blue on the outer,
and red in the centre. Between two rings there
appears a silver white interval. The rings

which are farthest from the centre are always

nearer together : they are composed of red and
green without a perceptible white space be
tween them.

434 .

We will now observe the appearances in their

gradual formation, beginning from the slightest
pressure .

435 .

On the slightest pressure the centre itself ap

pears of a green colour. Then follow as far as
the concentric circles extend, red and green

rings. They are wide, accordingly, and no trace

of a silver white space is to be seen between
them . The green is produced by the blue of an
imperfectly developed circle, mixing with the
yellow of the first circle. All the remaining
circles are, in this slight contact, broad ; their
yellow and blue edges mix together, thus pro
ducing a beautiful green . The red, however, of
 EPOPTICAL COLOURS . 181

each circle, remains pure and untouched ; hence

the whole series is composed of these two
colours .

436 .

A somewhat stronger pressure separates the

first circle by a slight interval from the imper
fectly developed one : it is thus detached,
and may be said to appear in a complete state.
The centre is now a blue point ; for the yellow
of the first circle is now separated from this
central point by a silver white space. From the
centre of the blue a red appears, which is thus ,
in all cases, bounded on the outside by its blue
edge. The second and , third rings from the
centre are quite detached . Where deviations
from this order present themselves , the observer
will be enabled to account for them, from what
has been or remains to be stated .

437 .

On a stronger pressure the centre becomes

yellow ; this yellow is surrounded by a red and

blue edge at last, the yellow also retires from

the centre ; the innermost circle is formed and

is bounded with yellow. The whole centre itself

now appears silver white, till at last, on the

strongest pressure , the dark point appears, and

the phenomenon , as described at first, is com
plete.
182 EPOPTICAL COLOURS .

438.

The relative size of the concentric circles and

their intervals depends on the form of the

glasses which are pressed together.

439 .

We remarked above, that the coloured centre

is, in fact, an undeveloped circle. It is, how-
ever, often found , on the slightest pressure, that
several undeveloped circles exist there, as it
were, in the germ ; these can be successively
developed before the eye of the observer.

440.

The regularity of these rings is owing to the

form of the convex glasses, and the diameter of
the coloured appearance depends on the greater
or lesser section of a circle on which a lens is

polished . We easily conclude from this , that

by pressing plane glasses together, irregular

appearances only will be produced ; the colours,
in fact, undulate like watered silks , and spread
from the point of pressure in all directions . Yet,
the phenomenon as thus exhibited is much more
splendid than in the former instance, and cannot
fail to strike every spectator. If we make the
experiment in this mode, we shall distinctly see,
as in the other case, that, on a slight pressure,

the green and red waves appear ; on a stronger,

stripes of blue, red , and yellow, become de-
 EPOPTICAL COLOURS . 183

tached. At first, the outer sides of these stripes

touch ; on increased pressure they are separated
by a silver white space.

441 .

Before we proceed to a further description of

this phenomenon, we may point out the most
convenient mode of exhibiting it. Place a large
convex glass on a table near the window ; upon
this glass lay a plate of well -polished mirror
glass, about the size of a playing-card , and the
mere weight of the plate will press sufficiently
to produce one or other of the phenomena above
described . So, also, by the different weight of
plates of glass, by other accidental circum

stances, for instance, by slipping the plate on

the side of the convex glass where the pressure
cannot be so strong as in the centre, all the
gradations above described can be produced in
succession .

442.

In order to observe the phenomenon it is

necessary to look obliquely on the surface where
it appears. But, above all , it is to be remarked

that by stooping still more, and looking at the

appearance under a more acute angle, the

circles not only grow larger but other circles are

developed from the centre, of which no trace is
to be discovered when we look perpendicularly,
even through the strongest magnifiers .
184 EPOPTICAL COLOURS .

443 .

In order to exhibit the phenomenon in its

greatest beauty, the utmost attention should be

paid to the cleanness of the glasses. If the ex

periment is made with plate-glass adapted for
mirrors, the glass should be handled with gloves .
The inner surfaces, which must come in contact

with the utmost nicety, may be most conve

niently cleaned before the experiment, and the

outer surfaces should be kept clean while the
pressure is increased .

444 .

From what has been said it will be seen that

an exact contact of two smooth surfaces is

necessary. Polished glasses are best adapted

for the purpose . Plates of glass exhibit the

most brilliant colours when they fit closely

together, and for this reason the phenomenon
will increase in beauty if exhibited under an
air- pump, by exhausting the air.

445 .

The appearance of the coloured rings may be

produced in the greatest perfection by placing a

convex and concave glass together which have
been ground on similar segments of circles . I
have never seen the effect more brilliant than

with the object- glass of an achromatic telescope,

 EPOPTICAL COLOURS . 185

in which the crown-glass and flint-glass were

necessarily in the closest contact.

446 .

A remarkable appearance takes place when

dissimilar surfaces are pressed together ; for

example, a polished crystal and a plate of

glass . The appearance does not at all exhibit
itself in large flowing waves , as in the combina
tion of glass with glass , but it is small and
angular, and , as it were, disjointed : thus it
appears that the surface of the polished crystal ,
which consists of infinitely small sections of
lamellæ, does not come so uninterruptedly in
contact with the glass as another glass - plate
would.

447 .

The appearance of colour vanishes on the

strongest pressure, which so intimately unites

the two surfaces that they appear to make but
one substance . It is this which occasions the

dark centre, because the pressed lens no longer

reflects any light from this point, for the very
same point, when seen against the light, is per
fectly clear and transparent . On relaxing the
pressure, the colours, in like manner, gradually
diminish, and disappear entirely when the sur
faces are separated .
186 EPOPTICAL COLOURS .

448 .

These same appearances occur in two similar

cases . If entirely transparent masses become

partially separated, the surfaces of their parts

being still sufficiently in contact, we see the
same circles and waves more or less . They may

be produced in great beauty by plunging a hot

mass of glass in water ; the different fissures and
cracks enabling us to observe the colours in
various forms . Nature often exhibits the same

phenomena in split rock crystals .

449 .

This appearance, again , frequently displays

itself in the mineral world in those kinds of

stone which by nature have a tendency to ex

foliate . These original lamellæ are, it is true,
so intimately united, that stones of this kind
appear altogether transparent and colourless ,
yet, the internal layers become separated , from
various accidental causes , without altogether

destroying the contact : thus the appearance,

which is now familiar to us by the foregoing
description, often occurs in nature, particularly
in calcareous spars ; the specularis, adularia,
and other minerals of similar structure . Hence

it shows an ignorance of the proximate causes

of an appearance so often accidentally produced ,

to consider it so important in mineralogy, and
to attach especial value to the specimens ex
hibiting it.
 EPOPTICAL COLOURS . 187

450.

We have yet to speak of the very remarkable

inversion of this appearance, as related by men

of science. If, namely, instead of looking at
the colours by a reflected light, we examine
them by a transmitted light, the opposite colours
are said to appear, and in a mode corresponding
with that which we have before described as

physiological ; the colours evoking each other.

Instead of blue, we should thus see red-yellow ;

instead of red, green , & c . , and vice versa. We

reserve experiments in detail, the rather as we
have ourselves still some doubts on this point.

451 .

If we were now called upon to give some ge-

neral explanation of these epoptical colours , as
they appear under the first condition , and to
show their connexion with the previously de-
tailed physical phenomena , we might proceed to
do so as follows :-

452.

The glasses employed for the experiments are

to be regarded as the utmost possible practical
approach to transparence . By the intimate
contact, however, occasioned by the pressure

applied to them, their surfaces, we are per-

suaded, immediately become in a very slight

degree dimmed . Within this semi-transparence

188 EPOPTICAL COLOURS .

the colours immediately appear, and every circle

comprehends the whole scale ; for when the two

opposites, yellow and blue, are united by their
red extremities, pure red appears : the green ,
on the other hand , as in prismatic experiments ,
when yellow and blue touch .

453.

We have already repeatedly found that where

colour exists at all, the whole scale is soon
called into existence ; a similar principle may be
said to lurk in the nature of every physical

phenomenon ; it already follows, from the idea

of polar opposition , from which an elementary

unity or completeness results .

454.

The fact that a colour exhibited by trans

mitted light is different from that displayed by
reflected light, reminds us of those dioptrical
colours of the first class which we found were

produced precisely in the same way through

semi-opacity. That here, too, a diminution of
transparency exists there can scarcely be a
doubt ; for the adhesion of the perfectly smooth
plates of glass (an adhesion so strong that they
remain hanging to each other) produces a de
gree of union which deprives each of the two
surfaces, in some degree, of its smoothness and

transparence . The fullest proof may, however,

 EPOPTICAL COLOURS. 189

be found in the fact that in the centre, where

the lens is most strongly pressed on the other

glass, and where a perfect union is accom
plished, a complete transparence takes place,
in which we no longer perceive any colour. All
this may be hereafter confirmed in a recapitula
tion of the whole.

455.

Second condition .-If after breathing on a

plate of glass , the breath is merely wiped away
with the finger, and if we then again imme
diately breathe on the glass , we see very vivid
colours gliding through each other ; these, as
the moisture evaporates, change their place,
and at last vanish altogether . If this operation

is repeated, the colours are more vivid and

beautiful, and remain longer than they did the
first time.

456.

Quickly as this appearance passes , and con

fused as it appears to be, I have yet remarked
the following effects :-At first all the principal
colours appear with their combinations ; on
breathing more strongly, the appearance may
be perceived in some order. In this succession
it may be remarked , that when the breath in
evaporating becomes contracted from all sides
190 EPOPTICAL COLOURS.

towards the centre, the blue colour vanishes

last.

457 .

The phenomenon appears most readily between

the minute lines, which the action of passing
the fingers leaves on the clear surface ; a some
what rough state of the surface of the glass is
otherwise requisite . On some glass the appear
ance may be produced by merely breathing ; in
other cases the wiping with the fingers is neces
sary I have even met with polished mirror
glasses , one side of which immediately showed
the colours vividly ; the other not . To judge
from some remaining pieces , the former was ori
ginally the front of the glass, the latter the side
which was covered with quicksilver.

458 .

These experiments may be best made in cold

weather, because the glass may be more quickly
and distinctly breathed upon, and the breath
evaporates more suddenly. In severe frost the
phenomenon may be observed on a large scale

while travelling in a carriage ; the glasses being

well cleaned , and all closed . The breath of the
persons within is very gently diffused over the
glass, and immediately produces the most vivid
play of colours. How far they may present a
regular succession I have not been able to re
 EPOPTICAL COLOURS . 191

mark ; but they appear particularly vivid when

they have a dark object as a background . This
alternation of colours does not, however, last

long ; for as soon as the breath gathers in

drops , or freezes to points of ice , the appear
ance is at once at an end .

459 .

Third condition. -The two foregoing experi

ments of the pressure and breathing may be

united ; namely, by breathing on a plate of glass,
i
and immediately after pressing the other upon t.
The colours then appear as in the case of two
glasses unbreathed upon, with this difference,
that the moisture occasions here and there an
interruption of the undulations . On pushing
one glass away from the other the moisture ap
pears iridescent as it evaporates.

460 .

It might, however, be asserted that this com

bined experiment exhibits no more than each
single experiment ; for it appears the colours
excited by pressure disappear in proportion as
the glasses are less in contact, and the moisture
then evaporates with its own colours.

461 .

Fourth condition .-Iridescent appearances

are observable in almost all bubbles ; soap
192 EPOPTICAL COLOURS .

bubbles are the most commonly known, and the

effect in question is thus exhibited in the easiest
mode ; but it may be observed in wine , beer, in
pure spirit, and again, especially, in the froth of
chocolate.

462 .

As in the above cases we required an infi

nitely narrow space between two surfaces which

are in contact, so we can consider the pellicle of

the soap-bubble as an infinitely thin lamina be
tween two elastic bodies ; for the appearance in

fact takes place between the air within , which

distends the bubble, and the atmospheric air.

463.

The bubble when first produced is colourless ;

then coloured stripes , like those in marble
paper, begin to appear : these at length spread
over the whole surface, or rather are driven
round it as it is distended .

464 .

In a single bubble, suffered to hang from the

straw or tube, the appearance of colour is diffi

cult to observe, for the quick rotation prevents
any accurate observation , and all the colours

seem to mix together ; yet we can perceive that

the colours begin at the orifice of the tube. The
solution itself may, however, be blown into care
 EPOPTICAL COLOURS. 193

fully, so that only one bubble shall appear. This

remains white (colourless) if not much agitated ;
but if the solution is not too watery , circles ap-
pear round the perpendicular axis of the bubble ;
these being near each other, are commonly com-
posed alternately of green and red . Lastly,
several bubbles may be produced together by
the same means ; in this case the colours appear
on the sides where two bubbles have pressed
each other flat.

465.

The bubbles of chocolate-froth may perhaps

be even more conveniently observed than those
of soap ; though smaller, they remain longer.
In these, owing to the heat, an impulse, a move-
ment, is produced and sustained , which appears
necessary to the development and succession
of the appearances .

466 .

If the bubble is small, or shut in between

others, coloured lines chase each other over the

surface, resembling marbled paper ; all the co-

lours of the scale are seen to pass through each
other ; the pure, the augmented, the combined,
all distinctly clear and beautiful . In small

bubbles the appearance lasts for a considerable

time .
 194 EPOPTICAL COLOURS.

467.

If the bubble is larger, or if it becomes by

degrees detached, owing to the bursting of others
near, we perceive that this impulsion and at
traction of the colours has , as it were, an end in

view ; for on the highest point of the bubble we

see a small circle appear, which is yellow in the
centre ; the other remaining coloured lines move
constantly round this with a vermicular action .

468.

In a short time the circle enlarges and sinks

downwards on all sides ; in the centre the
yellow remains ; below and on the outside it
becomes red, and soon blue ; below this again ap
pears a new circle of the same series of colours :
if they approximate sufficiently, a green is pro

duced by the union of the border- colours.

469.

When I could count three such leading cir

cles , the centre was colourless , and this space

became by degrees larger as the circles sank

lower, till at last the bubble burst .

470 .

Fifth condition . -Very delicate pellicles may

be formed in various ways : on these films we
discover a very lively play of colours, either in
the usual order, or more confusedly passing
through each other. The water in which lime
 EPOPTICAL COLOURS. 195

has been slaked soon skims over with a coloured

pellicle : the same happens on the surface of

stagnant water, especially if impregnated with
iron. The lamellæ of the fine tartar which

adheres to bottles, especially in red French

wine, exhibit the most brilliant colours, on

being exposed to the light, if carefully detached .

Drops of oil on water, brandy, and other fluids ,

produce also similar circles and brilliant effects :
but the most beautiful experiment that can be
made is the following : -Let aqua fortis, not too

strong, be poured into a flat saucer, and then

with a brush drop on it some of the varnish
used by engravers to cover certain portions
during the process of biting their plates . After
quick commotion there presently appears a film
which spreads itself out in circles, and imme-
diately produces the most vivid appearances of
colour.

471 .

Sixth condition.- When metals are heated,

colours rapidly succeeding each other appear on
the surface : these colours can, however, be ar-
rested at will.

472.

If a piece of polished steel is heated , it will ,

at a certain degree of warmth, be overspread
with yellow. If taken suddenly away from the
fire, this yellow remains .
02
196 EPOPTICAL COLOURS .

473 .

As the steel becomes hotter, the yellow ap-

pears darker, intenser, and presently passes into

red . This is difficult to arrest, for it hastens
very quickly to bright blue .

474 .

This beautiful blue is to be arrested if the

steel is suddenly taken out of the heat and bu-

ried in ashes . The blue steel works are pro-

duced in this way. If, again, the steel is held

longer over the fire, it soon becomes a light blue,
and so it remains .

475.

These colours pass like a breath over the

plate of steel ; each seems to fly before the
other, but, in reality, each successive hue is
constantly developed from the preceding one.

476 .

If we hold a penknife in the flame of a light,

a coloured stripe will appear across the blade.
The portion of the stripe which was nearest to
the flame is light blue ; this melts into blue-
red ; the red is in the centre ; then follow yellow-
red and yellow .

477.

This phenomenon is deducible from the pre-

 EPOPTICAL COLOURS . 197

ceding ones ; for the portion of the blade next

the handle is less heated than the end which is
in the flame, and thus all the colours which in
other cases exhibited themselves in succession ,

must here appear at once, and may thus be

permanently preserved .

478 .

Robert Boyle gives this succession of colours

as follows :-" A florido flavo ad flavum saturum

et rubescentem (quem artifices sanguineum vo

cant) inde ad languidum, postea ad saturiorem
cyaneum ." This would be quite correct if the
words " languidus ” and “ saturior" were to change
places . How far the observation is correct, that
the different colours have a relation to the de
gree of temper which the metal afterwards
acquires, we leave to others to decide . The

colours are here only indications of the different

degrees of heat .- Note R.

479.

When lead is calcined , the surface is first

greyish . This greyish powder, with greater

heat, becomes yellow, and then orange . Silver ,
too, exhibits colours when heated ; the fracture

of silver in the process of refining belongs to

the same class of examples . When metallic
glasses melt, colours in like manner appear on
the surface.
198 EPOPTICAL COLOURS.

480 .

Seventh condition. - When the surface of glass

becomes decomposed . The accidental opacity

(blindwerden) of glass has been already no
ticed the term (blindwerden ) is employed to
denote that the surface of the glass is so affected
as to appear dim to us.

481 .

White glass becomes " blind" soonest ; cast,

and afterwards polished glass is also liable to
be so affected ; the bluish less , the green least.

482 .

Of the two sides of a plate of glass one is

called the mirror side ; it is that which in the
oven lies uppermost, on which one may observe
roundish elevations : it is smoother than the

other, which is undermost in the oven, and on

which scratches may be sometimes observed .

On this account the mirror side is placed facing
the interior of rooms, because it is less affected

by the moisture adhering to it from within, than

the other would be, and the glass is thus less
liable to become " blind ."

483.

This half-opacity or dimness of the glass as

sumes by degrees an appearance of colour
which may become very vivid, and in which
 EPOPTICAL COLOURS . 199

perhaps a certain succession , or otherwise regu

lar order, might be discovered

484.

Having thus traced the physical colours from

their simplest effects to the present instances,
where these fleeting appearances are found to
be fixed in bodies , we are , in fact, arrived at the

point where the chemical colours begin ; nay,

we have in some sort already passed those limits ;
a circumstance which may excite a favourable
prejudice for the consistency of our statement.
By way of conclusion to this part of our inquiry,
we subjoin a general observation , which may
not be without its bearing on the common con
necting principle of the phenomena that have
been adduced.

485 .

The colouring of steel and the appearances

analogous to it, might perhaps be easily deduced

from the doctrine of the semi-opaque mediums.
Polished steel reflects light powerfully : we may

consider the colour produced by the heat as a

slight degree of dimness : hence a bright yellow
must immediately appear ; this, as the dimness
increases, must still appear deeper, more con
densed, and redder, and at last pure and ruby
red. The colour has now reached the extreme

point of depth , and if we suppose the same de

200 EPOPTICAL COLOURS.

gree of semi -opacity still to continue, the dim-

ness would now spread itself over a dark ground,
first producing a violet, then a dark-blue, and at
last a light-blue, and thus complete the series of
the appearances .
We will not assert that this mode of explana-
tion will suffice in all cases ; our object is rather
to point out the road by which the all- compre-
hensive formula, the very key of the enigma,
may be at last discovered .- Note S.
 201

PART III.

CHEMICAL COLOURS .

486 .

WE give this denomination to colours which we

can produce, and more or less fix , in certain
bodies ; which we can render more intense ,

which we can again take away and communicate

to other bodies, and to which, therefore , we

ascribe a certain permanency : duration is their

prevailing characteristic .

487.

In this view the chemical colours were for-

merly distinguished with various epithets ; they

were called colores proprii, corporei, materiales,
veri, permanentes, fixi.

488 .

In the preceding chapter we observed how

the fluctuating and transient nature of the phy-
sical colours becomes gradually fixed , thus
forming the natural transition to our present
subject.
489.

Colour becomes fixed in bodies more or less

permanently ; superficially, or thoroughly.

490.

All bodies are susceptible of colour ; it can

202 CHEMICAL CONTRAST.

either be excited , rendered intense, and gra

dually fixed in them, or at least communicated
to them .

XXXIV.

CHEMICAL CONTRAST.

491 .

In the examination of coloured appearances we

had occasion everywhere to take notice of a

principle of contrast : so again , in approaching
the precincts of chemistry, we find a chemical

contrast of a remarkable nature. We speak

here, with reference to our present purpose ,

only of that which is comprehended under the

general names of acid and alkali.

492 .

We characterised the chromatic contrast, in

conformity with all other physical contrasts as

a more and less ; ascribing the plus to the yellow
side, the minus to the blue ; and we now find

that these two divisions correspond with the

chemical contrasts . The yellow and yellow- red
affect the acids , the blue and blue-red the
alkalis ; thus the phenomena of chemical co
lours , although still necessarily mixed up with
 CHEMICAL CONTRAST. 203

other considerations , admit of being traced with

sufficient simplicity .

493.

The principal phenomena in chemical colours

are produced by the oxydation of metals, and it
will be seen how important this consideration is
at the outset. Other facts which come into the

account, and which are worthy of attention , will

be examined under separate heads ; in doing

this we, however, expressly state that we only

propose to offer some preparatory suggestions to
the chemist in a very general way, without
entering into the nicer chemical problems and
questions , or presuming to decide on them. Our

object is only to give a sketch of the mode in

which, according to our conviction , the chemical
theory of colours may be connected with general
physics.

XXXV.

WHITE .

494 .

IN treating of the dioptrical colours of the first

class ( 155) we have already in some degree anti-
cipated this subject. Transparent substances
204 CHEMICAL CONTRAST .

may be said to be in the highest class of inor

ganic matter. With these , colourless semi
transparence is closely connected , and white

may be considered the last opaque degree of

this .

495 .

Pure water crystallised to snow appears

white , for the transparence of the separate
parts makes no transparent whole . Various

crystallised salts, when deprived to a certain

extent of moisture, appear as a white powder.
The accidentally opaque state of a pure trans
parent substance might be called white ; thus

pounded glass appears as a white powder. The

cessation of a combining power, and the ex
hibition of the atomic quality of the substance
might at the same time be taken into the ac
count.

496 .

The known undecomposed earths are , in their

pure state, all white. They pass to a state
of transparence by natural crystallization . Silex
becomes rock-crystal ; argile, mica ; magnesia,
talc ; calcareous earth and barytes appear trans

parent in various spars. - Note T.

497 .

As in the colouring of mineral bodies the

 CHEMICAL CONTRAST . 205

metallic oxydes will often invite our attention ,

we observe, in conclusion , that metals , when
slightly oxydated , at first appear white , as lead
is converted to white lead by vegetable acid.

XXXVI .

BLACK.

498 .

BLACK is not exhibited in so elementary a state

as white. We meet with it in the vegetable
kingdom in semi-combustion ; and charcoal , a
substance especially worthy of attention on
other accounts , exhibits a black colour. Again ,
if woods -for example, boards , owing to the
action of light, air, and moisture, are deprived
in part of their combustibility, there appears
first the grey then the black colour. So again ,
we can convert even portions of animal sub-
stance to charcoal by semi-combustion.

499.

In the same manner we often find that a sub-

oxydation takes place in metals when the black

colour is to be produced . Various metals, par-

ticularly iron , become black by slight oxyda-
206 CHEMICAL CONTRAST.

tion, by vinegar, by mild acid fermentations ;

for example, a decoction of rice, & c.

500.

Again, it may be inferred that a de-oxydation

may produce black . This occurs in the prepa
ration of ink , which becomes yellow by the
solution of iron in strong sulphuric acid, but
when partly de-oxydised by the infusion of gall
nuts, appears black .

XXXVII .

FIRST EXCITATION OF COLOUR.

501 .

In the division of physical colours, where semi

transparent mediums were considered , we saw
colours antecedently to white and black . In
the present case we assume a white and black

already produced and fixed ; and the question

is , how colour can be excited in them ?

502 .

Here, too, we can say, white that becomes

darkened or dimmed inclines to yellow ; black,
as it becomes lighter, inclines to blue. - Note U.
 FIRST EXCITATION OF COLOUR .
207

503.

Yellow appears on the active ( plus) side , im

mediately in the light, the bright, the white.
All white surfaces easily assume a yellow tinge ;
paper, linen, wool , silk, wax : transparent fluids
again, which have a tendency to combustion ,
easily become yellow ; in other words they
easily pass into a very slight state of semi- trans
parence .

504.
So again the ex ci te ment on the passive side ,
the tendency to obscure , dark , black, is imme
diately accompanied with blue, or rather with a
reddish- blue. Iron dissolved in sulphuric acid,

1 and much diluted with water, if held to the

light in a glass , exhibits a beautiful violet colour

as soon as a few drops only of the infusion of

gall- nuts are added . This colour presents the
peculiar hues of the dark topaz, the orphninon
of a burnt- red, as the ancients expressed it.

505 .
Whether any colour can be excited in the
pure earths by the chemical operations of na
ture and art, without the admixture of metallic
oxydes, is an important question , generally, in
deed, answered in the negative . It is perhaps
connected with the question- to what extent
208 FIRST EXCITATION OF COLOUR .

changes may be produced in the earths through

oxydation ?

506.

Undoubtedly the negation of the above ques-

tion is confirmed by the circumstance that

wherever mineral colours are found, some trace

of metal, especially of iron , shows itself ; we are

thus naturally led to consider how easily iron
becomes oxydised , how easily the oxyde of iron
assumes different colours, how infinitely divisi-
ble it is , and how quickly it communicates its
colour. It were to be wished, notwithstanding ,

that new experiments could be made in regard

to the above point, so as either to confirm or
remove any doubt.

507.

However this may be, the susceptibility of

the earths with regard to colours already existing

is very great ; aluminous earth is thus particu-

larly distinguished .

508 .

In proceeding to consider the metals , which

in the inorganic world have the almost exclu-

sive prerogative of appearing coloured , we

find that , in their pure, independent, natural
state, they are already distinguished from the
 FIRST EXCITATION OF COLOURS . 209

pure earths by a tendency to some one colour or

other.

509.

While silver approximates most to pure white,

-nay, really represents pure white, heightened
by metallic splendor, -steel, tin , lead , and so
forth, incline towards pale blue-grey ; gold , on
the other hand , deepens to pure yellow, copper
approaches a red hue, which, under certain
circumstances , increases almost to bright red,
but which again returns to a yellow golden
colour when combined with zinc .

510.

But if metals in their pure state have so

specific a determination towards this or that
exhibition of colour, they are, through the effect
of oxydation, in some degree reduced to a com-
mon character ; for the elementary colours now
come forth in their purity, and although this or
that metal appears to have a particular tend-
ency to this or that colour, we find some that
can go through the whole circle of hues, others,
that are capable of exhibiting more than one
colour ; tin, however, is distinguished by its
comparative inaptitude to become coloured.
We propose to give a table hereafter, showing
how far the different metals can be more or less
made to exhibit the different colours .
P
210 FIRST EXCITATION OF COLOURS .

511.

When the clean, smooth surface of a pure

metal , on being heated , becomes overspread with
a mantling colour, which passes through a series
of appearances as the heat increases , this , we are
persuaded, indicates the aptitude of the metal
to pass through the whole range of colours . We
find this phenomenon most beautifully exhibited
in polished steel ; but silver, copper, brass , lead,
and tin , easily present similar appearances . A
superficial oxydation is probably here taking
place, as may be inferred from the effects of the

operation when continued , especially in the

more easily oxydizable metals.

512.

The same conclusion may be drawn from the

fact that iron is more easily oxydizable by acid
liquids when it is red hot, for in this case the
two effects concur with each other. We observe ,
again, that steel, accordingly as it is hardened
in different stages of its colorification , may ex-
hibit a difference of elasticity : this is quite
natural, for the various appearances of colour
indicate various degrees of heat. *

513.

If we look beyond this superficial mantling,

See par. 478.

 FIRST EXCITATION OF COLOURS . 211

this pellicle of colour, we observe that as metals

are oxydized throughout their masses, white or
black appears with the first degree of heat, as
may be seen in white lead , iron , and quicksilver.

514.

If we examine further, and look for the actual

exhibition of colour, we find it most frequently

on the plus side. The mantling, so often men-

tioned , of smooth metallic surfaces begins with
yellow, Iron passes presently into yellow ochre,
lead from white lead to massicot, quicksilver

from æthiops to yellow turbith . The solutions

of gold and platinum in acids are yellow.

515 .

The exhibitions on the minus side are less fre-

quent. Copper slightly oxydized appears blue .

In the preparation of Prussian-blue, alkalis are
employed.

516 .

Generally, however, these appearances of co-

lour are of so mutable a nature that chemists

look upon them as deceptive tests , at least in

the nicer gradations . For ourselves, as we can
only treat of these matters in a general way, we
merely observe that the appearances of colour
in metals may be classed according to their
P 2
212 AUGMENTATION OF COLOUR.

origin, manifold appearance , and cessation, as

various results of oxydation , hyper-oxydation ,
ab-oxydation, and de-oxydation . *

XXXVIII .

AUGMENTATION OF COLOUR.+

517.

THE augmentation of colour exhibits itself as a

condensation , a fulness , a darkening of the hue.
We have before seen, in treating of colourless
mediums, that by increasing the degree of opa

city in the medium, we can deepen a bright

object from the lightest yellow to the intensest
ruby-red . Blue, on the other hand, increases
to the most beautiful violet, if we rarefy and
diminish a semi - opaque medium, itself lighted ,
but through which we see darkness ( 150 , 151 ) .

518 .

If the colour is positive , a similar colour ap

pears in the intenser state. Thus if we fill a
white porcelain cup with a pure yellow liquor,
the fluid will appear to become gradually redder

* As these terms are afterwards referred to (par. 525) , it was

necessary to preserve them.
↑ Steigerung, literally gradual ascent . See the note to par . 523.
 AUGMENTATION OF COLOUR. 213

towards the bottom, and at last appears orange.

If we pour a pure blue solution into another

cup, the upper portion will exhibit a sky-blue,
that towards the bottom , a beautiful violet. If
the cup is placed in the sun , the shadowed side ,

even of the upper portion , is already violet . If

we throw a shadow with the hand, or any
other substance, over the illumined portion, the
shadow in like manner appears reddish .

519 .

This is one of the most important appearances

connected with the doctrine of colours , for we

here manifestly find that a difference of quan

tity produces a corresponding qualified impres
sion on our senses . In speaking of the last

class of epoptical colours (452, 485) , we stated

our conjecture that the colouring of steel might
perhaps be traced to the doctrine of the semi

transparent mediums, and we would here again

recall this to the reader's recollection .

520.

All chemical augmentation of colour, again ,

is the immediate consequence of continued ex
citation . The augmentation advances constantly
and unremittingly, and it is to be observed that
the increase of intenseness is most common on

the plus side. Yellow iron ochre increases , as

well by fire as by other operations, to a very
 •
214 AUGMENTATION OF COLOUR.

strong red massicot is increased to red lead ,

turbith to vermilion , which last attains a very
high degree of the yellow- red. An intimate

saturation of the metal by the acid, and its se-

paration to infinity , take place together with the
above effects .

521 .

The augmentation on the minus side is less

frequent ; but we observe that the more pure

and condensed the Prussian- blue or cobalt glass

is prepared, the more readily it assumes a red-

dish hue and inclines to the violet.

522 .

The French have a happy expression for the

less perceptible tendency of yellow and blue

towards red : they say the colour has " un œil
de rouge," which we might perhaps express by
a reddish glance (einen röthlichen blick) .

XXXIX.

CULMINATION.*

523.

THIS is the consequence of still progressing aug-

mentation . Red, in which neither yellow nor

* Culmination, the original word. It might have been ren-

 CULMINATION . 215

blue is to be detected, here constitutes the

acme.

524.

If we wish to select a striking example of a

culmination on the plus side, we again find it
in the coloured steel, which attains the bright
red acme, and can be arrested at this point.

525 .

Were we here to employ the terminology be-

fore proposed, we should say that the first oxy-
dation produces yellow, the hyper-oxydation
yellow-red ; that here a kind of maximum exists,
and that then an ab-oxydation, and lastly a de-
oxydation takes place.

526.

High degrees of oxydation produce a bright

red . Gold in solution , precipitated by a solution
of tin, appears bright red : oxyde of arsenic , in
combination with sulphur, produces a ruby
colour.

527 .

How far, however, a kind of sub- oxydation

may co-operate in some culminations , is matter

for inquiry ; for an influence of alkalis on the

dered maximum of colour, but as the author supposes an ascent

through yellow and blue to red , his meaning is better expressed
by his own term .
216 CULMINATION .

yellow-red also appears to produce the culmina

tion ; the colour reaching the acme by being

forced towards the minus side .

528.

The Dutch prepare a colour known by the

name of vermilion , from the best Hungarian
cinnabar, which exhibits the brightest yellow
red . This vermilion is still only a cinnabar,
which, however, approximates the pure red , and
it may be conjectured that alkalis are used to
bring it nearer to the culminating point.

529.

Vegetable juices, treated in this way, offer

very striking examples of the above effects .

The colouring- matter of turmeric , annotto , dyer's

saffron , * and other vegetables, being extracted
with spirits of wine , exhibits tints of yellow,
yellow-red, and hyacinth-red ; these, by the ad
mixture of alkalis , pass to the culminating point,
and even beyond it to blue- red .

530.
No instance of a culmination on the minus

side has come to my knowledge in the mineral

and vegetable kingdoms . In the animal king
dom the juice of the murex is remarkable ; of
its augmentation and culmination on the minus
side, we shall hereafter have occasion to speak .

* Curcuma, Bixa Orellana, Carthamus Tinctorius .

 217

XL.

FLUCTUATION .

531 .

THE mutability of colour is so great , that even

those pigments , which may have been considered
to be defined and arrested , still admit of slight
variations on one side or the other. This muta

bility is most remarkable near the culminating

point, and is effected in a very striking manner
by the alternate employment of acids and alkalis.

532 .

To express this appearance in dyeing, the

French make use of the word 66 virer," to turn
from one side to the other ; they thus very

adroitly convey an idea which others attempt to

express by terms indicating the component
hues.

533.

The effect produced with litmus is one of the

most known and striking of this kind . This
colouring substance is rendered red-blue by
means of alkalis . The red-blue is very readily

changed to red- yellow by means of acids, and

again returns to its first state by again employ
ing alkalis . The question whether a culmi

nating point is to be discovered and arrested by

218 FLUCTUATION.

nice experiments, is left to those who are prac-

tised in these operations . Dyeing, especially
scarlet-dyeing , might afford a variety of ex-
amples of this fluctuation .

XLI .

PASSAGE THROUGH THE WHOLE SCALE.

534 .

THE first excitation and gradual increase of

colour take place more on the plus than on the
minus side . So, also, in passing through the
whole scale, colour exhibits itself most on the
plus side.

535.

A passage of this kind, regular and evident to

the senses, from yellow through red to blue, is

apparent in the colouring of steel .

536 .

The metals may be arrested at various points

of the colorific circle by various degrees and
kinds of oxydation .

537 .

As they also appear green , a question arises

whether chemists know any instance in the
 PASSAGE THROUGH THE WHOLE SCALE . 219

mineral kingdom of a constant transition from

yellow, through green, to blue, and vice versa.
Oxyde of iron, melted with glass , produces first
a green, and with a more powerful heat, a blue
colour.

538 .

We may here observe of green generally , that

it appears, especially in an atomic sense, and
certainly in a pure state, when we mix blue and

yellow but, again, an impure and dirty yellow

soon gives us the impression of green ; yellow
and black already produce green ; this, however,
is owing to the affinity between black and blue.
An imperfect yellow, such as that of sulphur,
gives us the impression of a greenish hue : thus ,
again, an imperfect blue appears green. The
green of wine bottles arises, it appears, from an
imperfect union of the oxyde of iron with the

glass . If we produce a more complete union

by greater heat, a beautiful blue-glass is the
result.

539.

From all this it appears that a certain chasm

exists in nature between yellow and blue, the
opposite characters of which , it is true, may be
done away atomically by due immixture, and,
thus combined, to green ; but the true recon-
ciliation between yellow and blue, it seems,
only takes place by means of red .
220 PASSAGE THROUGH THE WHOLE SCALE.

540.

The process, however, which appears un-

attainable in inorganic substances, we shall find
to be possible when we turn our attention to
organic productions ; for in these, the passage
through the whole circle from yellow, through
green and blue, to red, really takes place .

XLII.

INVERSION.

541 .

AGAIN, an immediate inversión or change to

the totally opposite hue, is a very remarkable
appearance which sometimes occurs ; at present,
we are merely enabled to adduce what follows .

542.

The mineral chameleon, a name which has

been given to an oxyde of manganese, may be
considered , in its perfectly dry state, as a green

powder. If we strew it in water, the green

colour displays itself very beautifully in the first
moment of solution , but it changes presently to
the bright red opposite to green , without any
apparent intermediate state.
 INVERSION. 221

543.

The same occurs with the sympathetic ink,

which may be considered a reddish liquid , but
which, when dried by warmth, appears as a

green colour on paper.

544.

In fact, this phenomenon appears to be owing

to the conflict between a dry and moist state, as
has been already observed, if we are not mis
taken , by the chemists. We may look to the
improvements of time to point out what may
further be deduced from these phenomena, and
to show what other facts they may be connected
with .

XLIII .

FIXATION.

545 .

MUTABLE as we have hitherto found colour to

be, even as a substance, yet under certain cir

cumstances it may at last be fixed.

546.

There are bodies capable of being entirely

converted into colouring matter : here it may be
said that the colour fixes itself in its own sub
222 FIXATION.

stance, stops at a certain point, and is there de

fined . Such colouring substances are found

throughout nature ; the vegetable world affords

a great quantity of examples, among which

some are particularly distinguished , and may be
considered as the representatives of the rest ;
such as , on the active side, madder, on the

passive side, indigo .

547.

In order to make these materials available in

use, it is necessary that the colouring quality in

them should be intimately condensed, and the
tinging substance refined , practically speaking,
to an infinite divisibility. This is accomplished
in various ways, and particularly by the well
known means of fermentation and decomposition .

548 .

These colouring substances now attach them

selves again to other bodies . Thus, in the

mineral kingdom they adhere to earths and

metallic oxydes ; they unite in melting with
glasses ; and in this case , as the light is trans
mitted through them, they appear in the greatest
beauty, while an eternal duration may be as
cribed to them.

549.

They fasten on vegetable and animal bodies

with more or less power, and remain more or less
 FIXATION. 223

permanently ; partly owing to their nature,—as

yellow, for instance, is more evanescent than
blue, or owing to the nature of the substance on
which they appear. They last less in vegetable
than in animal substances, and even within this

latter kingdom there are again varieties . Hemp

or cotton threads , silk or wool , exhibit very
different relations to colouring substances.

550.

Here comes into the account the important

operation of employing mordants, which may
be considered as the intermediate agents be

tween the colour and the recipient substance ;

various works on dyeing speak of this circum
stantially . Suffice it to have alluded to pro
cesses by means of which the colour retains a
permanency only to be destroyed with the sub

stance, and which may even increase in bright

ness and beauty by use.

XLIV .

INTERMIXTURE, REAL.

551 .

EVERY intermixture pre-supposes a specific

state of colour ; and thus when we speak of in
termixture, we here understand it in an atomic
224 INTERMIXTURE, REAL.

sense. We must first have before us certain

bodies arrested at any given point of the colorific

circle , before we can produce gradations by their
union.

552.

Yellow, blue, and red , may be assumed as

pure elementary colours, already existing ; from
these , violet, orange, and green , are the simplest
combined results .

553.

Some persons have taken much pains to de-

fine these intermixtures more accurately , by

relations of number, measure, and weight , but

nothing very profitable has been thus accom-
plished.

554 .

Painting consists, strictly speaking, in the

intermixture of such specific colouring bodies
and their infinite possible combinations -com-
binations which can only be appreciated by the
nicest, most practised eye, and only accom-
plished under its influence .

555.

The intimate combination of these ingredients

is effected , in the first instance, through the most

perfect comminution of the material by means

of grinding, washing, &c. , as well as by vehicles
 INTERMIXTURE, REAL . 225

or liquid mediums which hold together the pul

verized substance, and combine organically,
as it were, the unorganic ; such are the oils ,
resins , & c.- Note V.

556 .

If all the colours are mixed together they re

tain their general character as σκιερὸν, and as

they are no longer seen next each other, no
completeness, no harmony, is experienced ; the
result is grey, which, like apparent colour,
always appears somewhat darker than white,
and somewhat lighter than black .

557 .

This grey may be produced in various ways .

By mixing yellow and blue to an emerald
green, and then adding pure red, till all three
neutralize each other ; or, by placing the primi
tive and intermediate colours next each other

in a certain proportion , and afterwards mixing

them .

558 .

That all the colours mixed together produce

white, is an absurdity which people have credu

lously been accustomed to repeat for a century,
in opposition to the evidence of their senses.

559.

Colours when mixed together retain their

226 INTERMIXTURE, REAL .

original darkness . The darker the colours, the

darker will be the grey resulting from their
union , till at last this grey approaches black .
The lighter the colours the lighter will be the
grey, which at last approaches white .

XLV .

INTERMIXTURE, APPARENT.

560.

THE intermixture, which is only apparent ,

naturally invites our attention in connexion with

the foregoing ; it is in many respects important,

and , indeed , the intermixture which we have
distinguished as real, might be considered as
merely apparent. For the elements of which
the combined colour consists are only too small
to be considered as distinct parts . Yellow and
blue powders mingled together appear green to

the naked eye, but through a magnifying glass

we can still perceive yellow and blue distinct
from each other. Thus yellow and blue stripes
seen at a distance, present a green mass ; the
same observation is applicable with regard to
the intermixture of other specific colours .

561 .

In the description of our apparatus we shall

 INTERMIXTURE, APPARENT. 227

have occasion to mention the wheel by means of

which the apparent intermixture is produced
by rapid movement . Various colours are ar-

ranged near each other round the edge of a

disk , which is made to revolve with velocity,
and thus by having several such disks ready,
every possible intermixture can be presented to
the eye, as well as the mixture of all colours to

grey, darker or lighter, according to the depth

of the tints as above explained .

562 .

Physiological colours admit, in like manner,

of being mixed with others . If, for example,
we produce the blue shadow (65) on a light
yellow paper, the surface will appear green .
The same happens with regard to the other
colours if the necessary preparations are at-
tended to.

563.

If, when the eye is impressed with visionary

images that last for a while , we look on coloured

surfaces, an intermixture also takes place ; the

spectrum is determined to a new colour which
is composed of the two.

564.

Physical colours also admit of combination.

Here might be adduced the experiments in

Q 2
228 INTERMIXTURE, APPARENT.

which many- coloured images are seen through

the prism , as we have before shown in detail

(258, 284) .

565.

Those who have prosecuted these inquiries

have, however, paid most attention to the ap
pearances which take place when the prismatic
colours are thrown on coloured surfaces .

566.

What is seen under these circumstances is

quite simple. In the first place it must be re

membered that the prismatic colours are much
more vivid than the colours of the surface on

which they are thrown . Secondly, we have

to consider that the prismatic colours may be
either homogeneous or heterogeneous , with the
recipient surface . In the former case the sur
face deepens and enhances them, and is itself
enhanced in return , as a coloured stone is
displayed by a similarly coloured foil. In the
opposite case each vitiates, disturbs , and des
troys the other.

567 .

These experiments may be repeated with

coloured glasses , by causing the sun-light to
shine through them on coloured surfaces . In
every instance similar results will appear.
 INTERMIXTURE, APPARENT. 229

568.

The same effect takes place when we look on

coloured objects through coloured glasses ; the
colours being thus according to the same con
ditions enhanced, subdued , or neutralized .

569.

If the prismatic colours are suffered to pass

through coloured glasses, the appearances that
take place are perfectly analogous ; in these
cases more or less force, more or less light and
dark , the clearness and cleanness of the glass
are all to be allowed for, as they produce many
delicate varieties of effect : these will not escape

the notice of every accurate observer who takes

sufficient interest in the inquiry to go through

the experiments .
570.

It is scarcely necessary to mention that

several coloured glasses, as well as oiled or
transparent papers ,placed over each other,
may be made to produce and exhibit every kind

of intermixture at pleasure .

571 .

Lastly, the operation of glazing in painting

belongs to this kind of intermixture ; by this
means a much more refined union may be pro

duced than that arising from the mechanical ,

atomic mixture which is commonly employed .
 230

XLVI .

COMMUNICATION, ACTUAL.

572.

HAVING now provided the colouring materials,

as before shown , a further question arises how
to communicate these to colourless substances :

the answer is of the greatest importance from

the connexion of the object with the ordinary
wants of men, with useful purposes, and with
commercial and technical interests .

573.

Here, again, the dark quality of every colour

again comes into the account. From a yellow
that is very near to white, through orange, and
the hue of minium to pure red and carmine,
through all gradations of violet to the deepest
blue which is almost identified with black ,
colour still increases in darkness . Blue once

defined , admits of being diluted , made light,

united with yellow, and then , as green, it ap
proaches the light side of the scale : but this is
by no means according to its own nature.

574.

In the physiological colours we have already

seen that they are less than the light, inasmuch
 COMMUNICATION, ACTUAL . 231

as they are a repetition of an impression of

light, nay, at last they leave this impression
quite as a dark . In physical experiments the
employment of semi-transparent mediums, the
effect of semi-transparent accessory images ,
taught us that in such cases we have to do with
a subdued light, with a transition to darkness .

575.

In treating of the chemical origin of pigments

we found that the same effect was produced on
the very first excitement. The yellow tinge
which mantles over the steel, already darkens
the shining surface. In changing white lead to
massicot it is evident that the yellow is darker
than white .

576.

This process is in the highest degree delicate ;

the growing intenseness , as it still increases,
tinges the substance more and more intimately
and powerfully , and thus indicates the extreme
fineness, and the infinite divisibility of the
coloured atoms .

577.

The colours which approach the dark side,

and consequently, blue in particular, can be
made to approximate to black ; in fact, a very
perfect Prussian blue , or an indigo acted on by
vitriolic acid appears almost as a black .
232 COMMUNICATION , ACTUAL.

578.

A remarkable appearance may be here ad

verted to ; pigments , in their deepest and most
condensed state , especially those produced from
the vegetable kingdom, such as the indigo just
mentioned, or madder carried to its intensest
hue, no longer show their own colour ; on the
contrary, a decided metallic shine is seen on
their surface, in which the physiological com

pensatory colour appears .

579.

All good indigo exhibits a copper- colour in its

fracture, a circumstance attended to , as a known
characteristic, in trade. Again , the indigo which
has been acted on by sulphuric acid , if thickly
laid on , or suffered to dry so that neither white

paper nor the porcelain can appear through,

exhibits a colour approaching to orange.

580.

The bright red Spanish rouge, probably pre

pared from madder, exhibits on its surface a

perfectly green, metallic shine . If this colour,
or the blue before mentioned , is washed with a
pencil on porcelain or paper, it is seen in its
real state owing to the bright ground shining
through .
581 .

Coloured liquids appear black when no light

 COMMUNICATION, ACTUAL. 233

is transmitted through them, as we may easily

see in cubic tin vessels with glass bottoms . In

these every transparent - coloured infusion will

appear black and colourless if we place a black

surface under them .

582.

If we contrive that the image of a flame be

reflected from the bottom, the image will appear

coloured . If we lift up the vessel and suffer the

transmitted light to fall on white paper under it,
the colour of the liquid appears on the paper.
Every light ground seen through such a coloured
medium exhibits the colour of the medium .

583.

Thus every colour, in order to be seen , must

have a light within or behind it. Hence the
lighter and brighter the grounds are , the more
brilliant the colours appear. If we pass lac-
varnish over a shining white metal surface, as
the so-called foils are prepared, the splendor of
the colour is displayed by this internally re-
flected light as powerfully as in any prismatic
experiment ; nay, the force of the physical co-
lours is owing principally to the circumstance
that light is always acting with and behind
them .

584 .

Lichtenberg, who of necessity followed the

234 COMMUNICATION, ACTUAL.

received theory, owing to the time and circum-

stances in which he lived, was yet too good an

observer, and too acute not to explain and clas-

sify, after his fashion , what was evident to his
senses . He says , in the preface to Delaval, “ It

appears to me also, on other grounds, probable,

that our organ , in order to be impressed by a
colour, must at the same time be impressed by
all light (white) ."
585.

To procure white as a ground is the chief

business of the dyer. Every colour may be

easily communicated to colourless earths, espe-

cially to alum but the dyer has especially to
do with animal and vegetable products as the
ground of his operations .

586.

Everything living tends to colour- to local ,

specific colour, to effect, to opacity- pervading

the minutest atoms . Everything in which life
is extinct approximates to white (494) , to the
abstract, the general state, to clearness ,* to
transparence .
587.

How this is put in practice in technical opera-

tions remains to be adverted to in the chapter

on the privation of colour. With regard to the

Verklärung, literally clarification.

 COMMUNICATION, APPARENT. 235

communication of colour, we have especially to

bear in mind that animals and vegetables, in a
living state, produce colours, and hence their

substances , if deprived of colours , can the more

readily re-assume them .

XLVII .

COMMUNICATION, APPARENT.

588.

THE Communication of colours , real as well as

apparent, corresponds, as may easily be seen,
with their intermixture : we need not, therefore,

repeat what has been already sufficiently en

tered into .

589.

Yet we may here point out more circumstan

tially the importance of an apparent communi

cation which takes place by means of reflection .
This phenomenon is well known , but still it is
pregnant with inferences , and is of the greatest
importance both to the investigator of nature
and to the painter.

590.

Let a surface coloured with any one of the

positive colours be placed in the sun , and let its
236 COMMUNICATION , APPARENT.

reflection be thrown on other colourless objects .

This reflection is a kind of subdued light, a
half-light, a half- shadow, which, in a subdued

state, reflects the colours in question .

591 .

If this reflection acts on light surfaces, it is

so far overpowered that we can scarcely per
ceive the colour which accompanies it ; but if it
acts on shadowed portions, a sort of magical
union takes place with the oxiεp . Shadow is
the proper element of colour, and in this case

a subdued colour approaches it, lighting up,

tinging, and enlivening it. And thus arises an
appearance, as powerful as agreeable, which
may render the most pleasing service to the
painter who knows how to make use of it.
These are the types of the so-called reflexes,
which were only noticed late in the history of
art, and which have been too seldom employed
in their full variety.

592.

The schoolmen called these colours colores na

tionales and intentionales, and the history of the

doctrine of colours will generally show that the
old inquirers already observed the phenomena
well enough, and knew how to distinguish them
properly, although the whole method of treating
such subjects is very different from ours.
 237

XLVIII.

EXTRACTION .

593.

COLOUR may be extracted from substances,

whether they possess it naturally or by com-
munication , in various ways. We have thus the
power to remove it intentionally for a useful
purpose, but, on the other hand, it often flies
contrary to our wish.

594.

Not only are the elementary earths in their

natural state white, but vegetable and animal
substances can be reduced to a white state with-
out disturbing their texture. A pure white is

very desirable for various uses , as in the instance

of our preferring to use linen and cotton stuffs
uncoloured . In like manner some silk stuffs ,

paper, and other substances, are the more agree-

able the whiter they can be. Again, the chief
basis of all dyeing consists in white grounds .
For these reasons manufacturers , aided by acci-
dent and contrivance, have devoted themselves
assiduously to discover means of extracting

colour : infinite experiments have been made

in connexion with this object, and many im-
portant facts have been arrived at.
238 EXTRACTION.

595.

It is in accomplishing this entire extraction of

colour that the operation of bleaching consists,
which is very generally practised empirically or
methodically . We will here shortly state the
leading principles.

596 .

Light is considered as one of the first means

of extracting colour from substances, and not

only the sun-light, but the mere powerless day-

light : for as both lights -the direct light of the
sun , as well as the derived light of the sky-
kindle Bologna phosphorus , so both act on co-
loured surfaces . Whether the light attacks the
colour allied to it, and, as it were, kindles and
consumes it, thus reducing the definite quality
to a general state, or whether some other opera-
tion , unknown to us , takes place, it is clear that
light exercises a great power on coloured sur-
faces , and bleaches them more or less . Here,
however, the different colours exhibit a different
degree of durability ; yellow, especially if pre-
pared from certain materials, is , in this case,
the first to fly.

597 .

Not only light, but air, and especially water,

act strongly in destroying colour. It has been
even asserted that thread, well soaked and
 EXTRACTION. 239

spread on the grass at night, bleaches better

than that which is exposed , after soaking, to the
sun-light. Thus , in this case, water proves to

be a solving and conducting agent, removing the

accidental quality, and restoring the substance
to a general or colourless state .

598.

The extraction of colour is also effected by

re-agents . Spirits of wine has a peculiar tend-
ency to attract the juice which tinges plants,
and becomes coloured with it often in a very

permanent manner . Sulphuric acid is very effi-

cient in removing colour, especially from wool
and silk, and every one is acquainted with the
use of sulphur vapours in bleaching.

599 .

The strongest acids have been recommended

more recently as more expeditious agents in

bleaching.

600.

The alkaline re-agents produce the same

effects by contrary means-lixiviums alone, oils
and fat combined with lixiviums to soap, and
so forth.

601 .

Before we dismiss this subject, we observe

240 EXTRACTION.

that it may be well worth while to make certain

delicate experiments as to how far light and air

exhibit their action in the removal of colour. It

might be possible to expose coloured substances

to the light under glass bells , without air, or

filled with common or particular kinds of air.
The colours might be those of known fugacity,
and it might be observed whether any of the
volatilized colour attached itself to the glass or

was otherwise perceptible as a deposit or preci

pitate ; whether, again , in such a case, this ap
pearance would be perfectly like that which had
gradually ceased to be visible , or whether it had
suffered any change . Skilful experimentalists
might devise various contrivances with a view
to such researches.

602.

Having thus first considered the operations of

nature as subservient to our purposes, we add a
few observations on the modes in which they
act against us .

603.

The art of painting is so circumstanced that

the most beautiful results of mind and labour are

altered and destroyed in various ways by time.

Hence great pains have been always taken to

find durable pigments , and so to unite them
with each other and with their ground , that their
 EXTRACTION. 241

permanency might be further insured . The

technical history of the schools of painting

affords sufficient information on this point.

604.

We may here, too, mention a minor art, to

which , in relation to dyeing, we are much in

debted , namely, the weaving of tapestry. As
the manufacturers were enabled to imitate the

most delicate shades of pictures, and hence

often brought the most variously coloured ma
terials together, it was soon observed that the
colours were not all equally durable, but that
some faded from the tapestry more quickly than
others . Hence the most diligent efforts were
made to ensure an equal permanency to all the
colours and their gradations . This object was
especially promoted in France, under Colbert,
whose regulations to this effect constitute an

epoch in the history of dyeing. The gay dye

which only aimed at a transient beauty , was
practised by a particular guild . On the other
hand, great pains were taken to define the
technical processes which promised durability.
And thus , after considering the artificial ex

traction , the evanescence , and the perishable

nature of brilliant appearances of colour, we
are again returned to the desideratum of per

manency.

R
 242

XLIX.

NOMENCLATURE .

605 .

AFTER what has been adduced respecting the

origin, the increase, and the affinity of colours ,
we may be better enabled to judge what nomen
clature would be desirable in future, and what
might be retained of that hitherto in use.

606 .

The nomenclature of colours, like all other

modes of designation, but especially those em

ployed to distinguish the objects of sense, pro
ceeded in the first instance from particular to

general, and from general back again to . par

ticular terms . The name of the species became
a generic name to which the individual was
again referred .

607.

This method might have been followed in

consequence of the mutability and uncertainty
of ancient modes of expression , especially since,
in the early ages, more reliance may be sup
posed to have been placed on the vivid impres
sions of sense . The qualities of objects were

described indistinctly, because they were im

pressed clearly on every imagination .
 NOMENCLATURE . 243

608 .

The pure chromatic circle was limited, it is

true ; but, specific as it was, it appears to have
been applied to innumerable objects , while it
was circumscribed by qualifying characteristics .
If we take a glance at the copiousness of the
Greek and Roman terms, we shall perceive how
mutable the words were, and how easily each
was adapted to almost every point in the colo-
rific circle.- Note W.
609.

In modern ages terms for many new grada-

tions were introduced in consequence of the

various operations of dyeing . Even the colours

of fashion and their designations, represented an

endless series of specific hues . We shall , on occa-

sion, employ the chromatic terminology of modern
languages , whence it will appear that the aim
has gradually been to introduce more exact de-
finitions, and to individualise and arrest a fixed
and specific state by language equally distinct.

610.

With regard to the German terminology, it

has the advantage of possessing four mono-
syllabic names no longer to be traced to their

origin, viz ., yellow ( Gelb) , blue, red, green .

They represent the most general idea of colour
to the imagination , without reference to any very
specific modification .
R 2.
244 NOMENCLATURE .

611.

If we were to add two other qualifying terms

to each of these four, as thus- red -yellow, and

yellow- red , red -blue and blue-red , yellow-green

and green-yellow, blue-green and green - blue, *
we should express the gradations of the chro-
matic circle with sufficient distinctness ; and if

we were to add the designations of light and

dark, and again define, in some measure , the
degree of purity or its opposite by the mono-
syllables black, white, grey, brown , we should
have a tolerably sufficient range of expressions
to describe the ordinary appearances presented
to us, without troubling ourselves whether they
were produced dynamically or atomically .

612.

The specific and proper terms in use might,

however, still be conveniently employed , and we
have thus made use of the words orange and
violet. We have in like manner employed the

word " purpur" to designate a pure central red,

because the secretion of the murex or "purpura"

is to be carried to the highest point of culmina-

tion by the action of the sun-light on fine linen
saturated with the juice.

* This description is suffered to remain because it accounts for

the terminology employed throughout.-T.
 245

L.

MINERALS.

613.

THE Colours of minerals are all of a chemical

nature, and thus the modes in which they are

produced may be explained in a general way by
what has been said on the subject of chemical
colours .

614.

Among the external characteristics of mine-

rals, the description of their colours occupies
the first place ; and great pains have been taken,
in the spirit of modern times, to define and arrest
every such appearance exactly : by this means ,
however , new difficulties , it appears to as, have
been created, which occasion no little incon-
venience in practice .

615.

It is true, this precision , when we reflect how

it arose, carries with it its own excuse. The

painter has at all times been privileged in the

use of colours . The few specific hues, in them-
selves , admitted of no change ; but from these,
innumerable gradations were artificially pro-
duced which imitated the surface of natural

objects . It was , therefore, not to be wondered

246 MINERALS .

at that these gradations should also be adopted

as criterions, and that the artist should be in-

vited to produce tinted patterns with which the

objects of nature might be compared, and
according to which they were to receive their
designations.

616.

But, after all , the terminology of colours which

has been introduced in mineralogy , is open to

many objections . The terms , for instance, have

not been borrowed from the mineral kingdom ,

as was possible enough in most cases, but

from all kinds of visible objects . Too many

specific terms have been adopted ; and in seek-

ing to establish new definitions by combining
these, the nomenclators have not reflected that

they thus altogether efface the image from the

imagination, and the idea from the understand-

ing. Lastly, these individual designations of

colours , employed to a certain extent as ele-
mentary definitions, are not arranged in the best
manner as regards their respective derivation
from each other : hence, the scholar must learn
every single designation , and impress an almost
lifeless but positive language on his memory.
The further consideration of this would be too

foreign to our present subject. *

These remarks have reference to the German mineralogical

terminology.-T.
 247

LI.

PLANTS.

617 .

THE Colours of organic bodies in general may be

considered as a higher kind of chemical opera-
tion , for which reason the ancients employed
the word concoction , és, to designate the
process . All the elementary colours, as well as
the combined and secondary hues, appear on

the surface of organic productions , while on the

other hand, the interior, if not colourless, ap-

pears , strictly speaking , negative when brought

to the light. As we propose to communicate
our views respecting organic nature, to a certain
extent, in another place, we only insert here
what has been before connected with the doc-

trine of colours , while it may serve as an intro-

duction to the further consideration of the views
alluded to and first, of plants .

618 .

Seeds, bulbs , roots , and what is generally shut

out from the light, or immediately surrounded
by the earth, appear, for the most part, white .

619.

Plants reared from seed, in darkness , are

white, or approaching to yellow. Light, on the

248 PLANTS .

other hand, in acting on their colours, acts at

the same time on their form.

620.

Plants which grow in darkness make, it is

true, long shoots from joint to joint : but the
stems between two joints are thus longer than

they should be ; no side stems are produced,

and the metamorphosis of the plant does not
take place .

621 .

Light, on the other hand, places it at once in

an active state ; the plant appears green, and
the course of the metamorphosis proceeds unin
terruptedly to the period of reproduction .

622.

We know that the leaves of the stem are only

preparations and pre-significations of the in
struments of florification and fructification , and
accordingly we can already see colours in the
leaves of the stem which, as it were, announce
the flower from afar, as is the case in the ama
ranthus .

623 .

There are white flowers whose petals have

wrought or refined themselves to the greatest

purity ; there are coloured ones , in which the

 PLANTS . 249

elementary hues may be said to fluctuate to and

fro . There are some which, in tending to the
higher state, have only partially emancipated
themselves from the green of the plant.

624.

Flowers of the same genus, and even of the

same kind , are found of all colours . Roses , and
particularly mallows, for example, vary through
a great portion of the colorific circle from white

to yellow, then through red-yellow to bright

red, and from thence to the darkest hue it can
exhibit as it approaches blue.

625 .

Others already begin from a higher degree

in the scale, as, for example, the poppy, which
is yellow-red in the first instance, and which
afterwards approaches a violet hue.

626.

Yet the same colours in species , varieties, and

even in families and classes, if not constant , are

still predominant, especially the yellow colour :

blue is throughout rarer.

627.

A process somewhat similar takes place in

the juicy capsule of the fruit, for it increases in
colour from the green, through the yellowish
250 PLANTS .

and yellow, up to the highest red, the colour of

the rind thus indicating the degree of ripeness.
Some are coloured all round , some only on the

sunny side, in which last case the augmentation

of the yellow into red, ― the gradations crowd-
ing in and upon each other, - may be very well
observed .

628.

Many fruits, too , are coloured internally ;

pure red juices , especially, are common .

629.

The colour which is found superficially in the

flower and penetratingly in the fruit, spreads
itself through all the remaining parts, colouring

the roots and the juices of the stem, and this

with a very rich and powerful hue.

630.

So, again, the colour of the wood passes from

yellow through the different degrees of red up

to pure red and on to brown . Blue woods are
unknown to me ; and thus in this degree of or-
ganisation the active side exhibits itself power-

fully, although both principles appear balanced

in the general green of the plant .

631 .

We have seen above that the germ pushing

 PLANTS. 251

from the earth is generally white and yellowish,

but that by means of the action of light and air

it acquires a green colour. The same happens
with young leaves of trees, as may be seen , for
example, in the birch, the young leaves of which
are yellowish, and if boiled, yield a beautiful
yellow juice afterwards they become greener,
while the leaves of other trees become gradually
blue-green.

632.

Thus a yellow ingredient appears to belong

more essentially to leaves than a blue one ; for
this last vanishes in the autumn , and the yellow
of the leaf appears changed to a brown colour .
Still more remarkable , however, are the parti
cular cases where leaves in autumn again be
come pure yellow, and others increase to the
brightest red .

633.

Other plants, again , may, by artificial treat

ment be entirely converted to a colouring
matter, which is as fine, active, and infinitely
divisible as any other. Indigo and madder,
with which so much is effected , are examples :
lichens are also used for dyes ..

634 .

To this fact another stands immediately op

252 WORMS, INSECTS , FISHES .

posed ; we can, namely, extract the colouring

part of plants, and, as it were, exhibit it apart,
while the organisation does not on this account
appear to suffer at all. The colours of flowers

may be extracted by spirits of wine, and tinge

it ; the petals meanwhile becoming white .

635.

There are various modes of acting on flowers

and their juices by re-agents . This has been
done by Boyle in many experiments . Roses
are bleached by sulphur, and may be restored
to their first state by other acids ; roses are
turned green by the smoke of tobacco.

LII.

WORMS, INSECTS , FISHES.

636 .

WITH regard to creatures belonging to the lower

degrees of organisation , we may first observe
that worms, which live in the earth and remain
in darkness and cold moisture, are imperfectly
negatively coloured ; worms bred in warm mois-
ture and darkness are colourless ; light seems
expressly necessary to the definite exhibition of
colour.
 WORMS, INSECTS , FISHES . 253

637 .

Creatures which live in water, which, although

a very dense medium, suffers sufficient light
to pass through it, appear more or less coloured .

Zoophytes, which appear to animate the purest

calcareous earth, are mostly white ; yet we find
corals deepened into the most beautiful yellow-
red in other cells of worms this colour increases

nearly to bright red .

638.

The shells of the crustaceous tribe are beauti-

fully designed and coloured, yet it is to be re-

marked that neither land-snails nor the shells
of crustacea of fresh water, are adorned with
such bright colours as those of the sea.

639.

In examining shells, particularly such as are

spiral, we find that a series of animal organs,
similar to each other, must have moved in-
creasingly forward , and in turning on an axis
produced the shell in a series of chambers , divi-
sions , tubes, and prominences, according to a
plan for ever growing larger. We remark , how-
ever, that a tinging juice must have accompanied
the development of these organs, a juice which
inarked the surface of the shell, probably through
the immediate co-operation of the sea- water,
with coloured lines, points , spots, and shadings :
254 WORMS, INSECTS, FISHES .

this must have taken place at regular intervals ,

and thus left the indications of increasing growth
lastingly on the exterior ; meanwhile the inte
rior is generally found white or only faintly co
loured.

640.

That such a juice is to be found in shell - fish

is, besides, sufficiently proved by experience ; for
the creatures furnish it in its liquid and colour
ing state : the juice of the ink-fish is an ex
ample. But a much stronger is exhibited in the
red juice found in many shell - fish, which
was so famous in ancient times, and has been

employed with advantage by the moderns .

There is, it appears , in the entrails of many of
the crustaceous tribe a certain vessel which is

filled with a red juice ; this contains a very

strong and durable colouring substance, so much
so that the entire creature may be crushed and
boiled , and yet out of this broth a sufficiently
strong tinging liquid may be extracted . But
the little vessel filled with colour may be sepa

rated from the animal, by which means of course

a concentrated juice is gained .

641 .

This juice has the property that when ex

posed to light and air it appears first yellowish,
then greenish ; it then passes to blue, then to a
 WORMS, INSECTS , FISHES. 255

violet, gradually growing redder ; and lastly, by

the action of the sun, and especially if trans
ferred to cambric, it assumes a pure bright red
colour.

642.

Thus we should here have an augmentation ,

even to culmination, on the minus side, which
we cannot easily meet with in inorganic cases ;
indeed, we might almost call this example a
passage through the whole scale, and we are

persuaded that by due experiments the entire

revolution of the circle might really be effected ,
for there is no doubt that by acids duly em
ployed, the pure red may be pushed beyond the

culminating point towards scarlet.

643.

This juice appears on the one hand to be con

nected with the phenomena of reproduction ,
eggs being found, the embryos of future shell
fish, which contain a similar colouring principle.
On the other hand, in animals ranking higher
in the scale of being, the secretion appears to
bear some relation to the development of the
blood . The blood exhibits similar properties in
regard to colour ; in its thinnest state it appears
yellow ; thickened , as it is found in the veins,
it appears red ; while the arterial blood exhibits

a brighter red , probably owing to the oxydation

256 WORMS, INSECTS , FISHES.

which takes place by means of breathing. The

venous blood approaches more to violet, and by
this mutability denotes the tendency to that
augmentation and progression which are now
familiar to us.

644 .

Before we quit the element whence we de

rived the foregoing examples , we may add a few
observations on fishes, whose scaly surface is
coloured either altogether in stripes, or in spots ,
and still oftener exhibits a certain iridescent

appearance, indicating the affinity of the scales

with the coats of shell-fish, mother- of- pearl, and
even the pearl itself. At the same time it

should not be forgotten that warmer climates,

the influence of which extends to the watery
regions, produce , embellish, and enhance these
colours in fishes in a still greater degree.

645 .

In Otaheite, Forster observed fishes with

beautifully iridescent surfaces, and this effect
was especially apparent at the moment when

the fish died . We may here call to mind the

hues of the chameleon, and other similar ap
pearances ; for when similar facts are presented
together, we are better enabled to trace them.

646 .

Lastly, although not strictly in the same

 WORMS , INSECTS , FISHES . 257

class, the iridescent appearance of certain mo-

luscæ may be mentioned , as well as the phos-
phorescence which, in some marine creatures,
it is said becomes iridescent just before it
vanishes .

647.

We now turn our attention to those creatures

which belong to light, air and dry warmth , and

it is here that we first find ourselves in the

living region of colours. Here, in exquisitely

organised parts, the elementary colours present
themselves in their greatest purity and beauty.

They indicate, however, that the creatures they

adorn, are still low in the scale of organis-
ation, precisely because these colours can thus
appear, as it were, unwrought. Here , too ,

heat seems to contribute much to their develop-

ment.

648 .

We find insects which may be considered

altogether as concentrated colouring matter ;
among these, the cochineals especially are cele-
brated ; with regard to these we observe that
their mode of settling on vegetables, and even
nestling in them, at the same time produces
those excrescences which are so useful as mor-

dants in fixing colours .

258 WORMS, INSECTS, FISHES.

649.

But the power of colour, accompanied by

regular organisation , exhibits itself in the most

striking manner in those insects which require

a perfect metamorphosis for their development
-in scarabæi , and especially in butterflies .

650.

These last, which might be called true pro

ductions of light and air, often exhibit the most
beautiful colours, even in their chrysalis state,
indicating the future colours of the butterfly ; a

consideration which, if pursued further hereafter,

must undoubtedly afford a satisfactory insight
into many a secret of organised being.

651 .

If, again, we examine the wings of the but

terfly more accurately, and in its net-like web
discover the rudiments of an arm, and observe
further the mode in which this, as it were, flat

tened arm is covered with tender plumage and

constituted an organ of flying ; we believe we
recognise a law according to which the great
variety of tints is regulated . This will be a
subject for further investigation hereafter.

652.

That, again, heat generally has an influence

 BIRDS . 259

on the size of the creature , on the accomplish-

ment of the form, and on the greater beauty of

the colours , hardly needs to be remarked .

LIII.

BIRDS.

653 .

THE more we approach the higher organisations ,

the more it becomes necessary to limit ourselves
to a few passing observations ; for all the natural
conditions of such organised beings are the re-

sult of so many premises, that, without having

at least hinted at these, our remarks would only
appear daring, and at the same time insufficient .

654 .

We find in plants, that the consummate

flower and fruit are, as it were, rooted in the
stem, and that they are nourished by more per-
fect juices than the original roots first afforded ;
we remark, too, that parasitical plants which
derive their support from organised structures,
exhibit themselves especially endowed as to
their energies and qualities . We might in some
sense compare the feathers of birds with plants
of this description ; the feathers spring up as a
last structural result from the surface of a body
s 2
260 BIRDS .

which has yet much in reserve for the comple

tion of the external economy, and thus are very
richly endowed organs .

655 .

The quills not only grow proportionally to a

considerable size , but are throughout branched ,
by which means they properly become feathers,
and many of these feathered branches are again
subdivided ; thus , again , recalling the structure
of plants .

656.

The feathers are very different in shape and

size, but each still remains the same organ ,

forming and transforming itself according to

the constitution of the part of the body from
which it springs .

657.

With the form , the colour also becomes

changed, and a certain law regulates the general

order of hues as well as that particular dis
tribution by which a single feather becomes
party coloured. It is from this that all com

bination of variegated plumage arises, and

whence, at last, the eyes in the peacock's tail
are produced . It is a result similar to that which
we have already unfolded in treating of the
metamorphosis of plants, and which we shall
take an early opportunity to prove.
 BIRDS . 261

658.

Although time and circumstances compel us

here to pass by this organic law, yet we are
bound to refer to the chemical operations which
commonly exhibit themselves in the tinting of
feathers in a mode now sufficiently known to us .

659.

Plumage is of all colours , yet, on the whole,

yellow deepening to red is commoner than blue:

660.

The operation of light on the feathers and

their colours , is to be remarked in all cases .
Thus, for example, the feathers on the breast of
certain parrots, are strictly yellow ; the scale
like anterior portion , which is acted on by the
light, is deepened from yellow to red . The
breast of such a bird appears bright-red, but if
we blow into the feathers the yellow appears .

661 .

The exposed portion of the feathers is in all

cases very different from that which, in a
quiet state , is covered ; it is only the exposed
portion , for instance, in ravens , which exhibits

the iridescent appearance ; the covered portion

does not from which indication , the feathers of
the tail when ruffled together, may be at once

placed in the natural order again .

 262

LIV .

MAMMALIA AND HUMAN BEINGS.

662.

HERE the elementary colours begin to leave us

altogether. We are arrived at the highest de
gree of the scale , and shall not dwell on its
characteristics long.

663.

An animal of this class is distinguished

among the examples of organised being. Every

thing that exhibits itself about him is living.
Of the internal structure we do not speak, but
confine ourselves briefly to the surface. The
hairs are already distinguished from feathers ,
inasmuch as they belong more to the skin , in
asmuch as they are simple, thread-like, not
branched . They are however, like feathers ,
shorter, longer, softer, and firmer, colourless
or coloured, and all this in conformity to laws
which might be defined .

664.

White and black , yellow, yellow- red and

brown, alternate in various modifications , but
they never appear in such a state as to remind
us of the elementary hues . On the contrary ,
 MAMMALIA AND HUMAN BEINGS. 263

they are all broken colours subdued by organic

concoction, and thus denote , more or less, the
perfection of life in the being they belong to.

665.

One of the most important considerations con

nected with morphology, so far as it relates to
surfaces, is this, that even in quadrupeds the
spots of the skin have a relation with the parts
underneath them . Capriciously as nature here
appears, on a hasty examination, to operate, she
nevertheless consistently observes a secret law.
The development and application of this , it is
true, are reserved only for accurate and careful
investigation and sincere co -operation .

666 .

If in some animals portions appear variegated

with positive colours, this of itself shows how
far such creatures are removed from a perfect
organisation ; for, it may be said, the nobler a
creature is , the more all the mere material of

which he is composed, is disguised by being

wrought together ; the more essentially his sur
face corresponds with the internal organisation ,
the less can it exhibit the elementary colours .
Where all tends to make up a perfect whole,
any detached specific developments cannot take
place .
667 .

Of man we have little to say, for he is en

264 MAMMALIA AND HUMAN BEINGS .

tirely distinct from the general physiological

results of which we now treat . So much in this

case is in affinity with the internal structure,

that the surface can only be sparingly endowed .

668 .

When we consider that brutes are rather en

cumbered than advantageously provided with

intercutaneous muscles ; when we see that

much that is superfluous tends to the surface,

as, for instance, large ears and tails, as well as
hair, manes, tufts ; we see that nature, in such

cases, had much to give away and to lavish.

669.

On the contrary, the general surface of the

human form is smooth and clean , and thus in
the most perfect examples the beautiful forms
are apparent ; for it may be remarked in pass
ing, that a superfluity of hair on the chest, arms,
and lower limbs , rather indicates weakness than
strength . Poets only have sometimes been in
duced, probably by the example of the ferine
nature, so strong in other respects, to extol
similar attributes in their rough heroes .

670.

But we have here chiefly to speak of colour,

and observe that the colour of the human skin ,
in all its varieties, is never an elementary co
 MAMMALIA AND HUMAN BEINGS . 265

lour, but presents, by means of organic concoc

tion, a highly complicated result.- Note X.

671 .

That the colour of the skin and hair has rela

tion with the differences of character, is beyond

question ; and we are led to conjecture that the
circumstance of one or other organic system

predominating, produces the varieties we see.

A similar hypothesis may be applied to nations,

in which case it might perhaps be observed , that
certain colours correspond with certain confirm
ations, which has always been observed of the
negro physiognomy .

672.

Lastly, we might here consider the problem

atical question , whether all human forms and
hues are not equally beautiful , and whether

custom and self-conceit are not the causes why

one is preferred to another ? We venture, how
ever, after what has been adduced , to assert that
the white man, that is, he whose surface varies

from white to reddish, yellowish, brownish, in

short, whose surface appears most neutral in
hue and least inclines to any particular or
positive colour, is the most beautiful. On the

same principle a similar point of perfection in

human conformation may be defined hereafter,
when the question relates to form . We do not
266 PHYSICAL AND CHEMICAL EFFECTS OF

imagine that this long -disputed question is to be

thus, once for all, settled , for there are persons

enough who have reason to leave this significancy

of the exterior in doubt ; but we thus express a

conclusion, derived from observation and reflec

tion, such as might suggest itself to a mind
aiming at a satisfactory decision . We subjoin
a few observations connected with the elemen
tary chemical doctrine of colours .- Note Y.

LV .

PHYSICAL AND CHEMICAL EFFECTS OF THE TRANSMIS

SION OF LIGHT THROUGH COLOURED MEDIUMS .

673.

THE physical and chemical effects of colourless

light are known, so that it is unnecessary here
to describe them at length. Colourless light
exhibits itself under various conditions as ex

citing warmth, as imparting a luminous quality

to certain bodies, as promoting oxydation and
de-oxydation. In the modes and degrees of

these effects many varieties take place, but no

difference is found indicating a principle of
contrast such as we find in the transmission of

coloured light. We proceed briefly to advert to

this.
 LIGHT THROUGH COLOURED MEDIUMS . 267

674.

Let the temperature of a dark room be ob

served by means of a very sensible air-thermo
meter ; if the bulb is then brought to the direct
sun light as it shines into the room, nothing is
more natural than that the fluid should indicate

a much higher degree of warmth . If upon this

we interpose coloured glasses , it follows again
quite naturally that the degree of warmth must

be lowered ; first, because the operation of the

direct light is already somewhat impeded by
the glass , and again, more especially, because a
coloured glass , as a dark medium, admits less
light through it.

675.

But here a difference in the excitation of

warmth exhibits itself to the attentive observer,
according to the colour of the glass . The yel
low and the yellow- red glasses produce a higher
temperature than the blue and blue- red , the
difference being considerable .

676.

This experiment may be made with the pris

matic spectrum . The temperature of the room

being first remarked on the thermometer, the

blue coloured light is made to fall on the bulb,
when a somewhat higher degree of warmth is
exhibited, which still increases as the other co
268 PHYSICAL AND CHEMICAL EFFECTS OF

lours are gradually brought to act on the mer-

cury. If the experiment is made with the water-
prism, so that the white light can be retained in
the centre, this, refracted indeed , but not yet co-
loured light, is the warmest ; the other colours ,
stand in relation to each other as before.

677.

As we here merely describe, without under-

taking to deduce or explain this phenomenon ,
we only remark in passing, that the pure light is
by no means abruptly and entirely at an end
with the red division in the spectrum, but that
a refracted light is still to be observed deviating
from its course and, as it were , insinuating itself
beyond the prismatic image, so that on closer
examination it will hardly be found necessary

to take refuge in invisible rays and their refrac-

tion .
678.

The communication of light by means of co-

loured mediums exhibits the same difference .

The light communicates itself to Bologna phos-

phorus through blue and violet glasses, but by
no means through yellow and yellow- red glasses .
It has been even remarked that the phosphori
which have been rendered luminous under violet

and blue glasses, become sooner extinguished

when afterwards placed under yellow and yel-
low-red glasses than those which have been
 LIGHT THROUGH COLOURED MEDIUMS . 269

suffered to remain in a dark room without any

further influence.

679 .

These experiments , like the foregoing, may

also be made by means of the prismatic spec

trum , when the same results take place.

680 .

To ascertain the effect of coloured light on

oxydation and de-oxydation , the following means
may be employed :-Let moist, perfectly white
muriate of silver* be spread on a strip of paper ;
place it in the light, so that it may become to a
certain degree grey, and then cut it in three
portions . Of these, one may be preserved in a
book, as a specimen of this state ; let another
be placed under a yellow-red, and the third
under a blue-red glass . The last will become a
darker grey, and exhibit a de-oxydation ; the
other, under the yellow-red glass, will, on the
contrary, become a lighter grey, and thus ap
proach nearer to the original state of more per
fect oxydation . The change in both may be
ascertained by a comparison with the unaltered
specimen .

681 .

An excellent apparatus has been contrived to

* Now generally called chloride of silver : the term in the

original is Hornsilber. - T .
270 CHEMICAL EFFECT IN

perform these experiments with the prismatic

image. The results are analogous to those al
ready mentioned , and we shall hereafter give
the particulars, making use of the labours of an
accurate observer, who has been for some time

carefully prosecuting these experiments . *

LVI .

CHEMICAL EFFECT IN DIOPTRICAL ACHROMATISM .

682.

WE first invite our readers to turn to what has

been before observed on this subject (285 , 298),

to avoid unnecessary repetition here.

683.

We can thus give a glass the property of

producing much wider coloured edges without
refracting more strongly than before, that is ,
without displacing the object much more per
ceptibly.

684 .

This property is communicated to the glass

by means of metallic oxydes. Minium, melted
and thoroughly united with a pure glass , pro

* The individual alluded to was Seebeck : the result of his ex

periments was published in the second volume .-T.
 DIOPTRICAL ACHROMATISM. 271

duces this effect, and thus flint-glass (291 ) is

prepared with oxyde of lead . Experiments of

this kind have been carried farther, and the so
called butter of antimony, which, according to
a new preparation , may be exhibited as a pure
fluid, has been made use of in hollow lenses
and prisms , producing a very strong appearance
of colour with a very moderate refraction , and
presenting the effect which we have called hy
perchromatism in a very vivid manner.

685.

In common glass, the alkaline nature ob

viously preponderates , since it is chiefly com
posed of sand and alkaline salts ; hence a series
of experiments, éxhibiting the relation of per
fectly alkaline fluids to perfect acids , might lead
to useful results .

686.

For, could the maximum and minimum be

found, it would be a question whether a refract
ing medium could not be discovered, in which
the increasing and diminishing appearance of

colour, ( an effect almost independent of refrac

tion,) could not be done away with altogether,

while the displacement of the object would be

unaltered .

687.

How desirable, therefore, it would be with

272 GENERAL REFLECTIONS .

regard to this last point, as well as for the elu

cidation of the whole of this third division of
our work, and, indeed , for the elucidation of the

doctrine of colours generally , that those who are

occupied in chemical researches, with new views
ever opening to them, should take this subject
in hand, pursuing into more delicate combina

tions what we have only roughly hinted at, and

prosecuting their inquiries with reference to
science as a whole.
 273

PART IV .

GENERAL CHARACTERISTICS .

688 .

We have hitherto, in a manner forcibly, kept

phenomena asunder, which, partly from their
nature, partly in accordance with our mental
habits, have, as it were, constantly sought to be
reunited. We have exhibited them in three
divisions . We have considered colours , first, as
transient, the result of an action and re-action

in the eye itself ; next, as passing effects of

colourless , light- transmitting, transparent, or

opaque mediums on light ; especially on the

luminous image ; lastly, we arrived at the point
where we could securely pronounce them as
permanent, and actually inherent in bodies .

689.

In following this order we have as far as pos

sible endeavoured to define , to separate, and to
class the appearances . But now that we need
no longer be apprehensive of mixing or con
founding them , we may proceed, first, to state
the general nature of these appearances con
sidered abstractedly, as an independent circle
of facts, and, in the next place, to show how
this particular circle is connected with other

classes of analogous phenomena in nature.

T
 274

THE FACILITY WITH WHICH COLOUR APPEARS .

690.
We have observed that colour under many

conditions appears very easily. The suscep

tibility of the eye with regard to light, the
constant re-action of the retina against it, pro

duce instantaneously a slight iridescence .

Every subdued light may be considered as
coloured , nay, we ought to call any light coloured ,
inasmuch as it is seen . Colourless light, colour
less surfaces , are, in some sort, abstract ideas ;
in actual experience we can hardly be said to be
aware of them .- Note Z.
691 .

If light impinges on a colourless body, is re

flected from it or passes through it, colour im
mediately appears ; but it is necessary here to
remember what has been so often urged by us,
namely, that the leading conditions of refrac
tion, reflection, & c. , are not of themselves suffi

cient to produce the appearance . Sometimes ,

it is true, light acts with these merely as light,
but oftener as a defined , circumscribed appear

ance, as a luminous image. The semi-opacity

of the medium is often a necessary condition ;
while half, and double shadows , are required

for many coloured appearances. In all cases,

however, colour appears instantaneously. We
find , again, that by means of pressure, breathing
heat (432, 471 ), by various kinds of motion and
 THE FORCE OF COLOUR. 275

alteration on smooth clean surfaces (461 ) , as

well as on colourless fluids (470) , colour is im-
mediately produced .

692.

The slightest change has only to take place

in the component parts of bodies , whether by
immixture with other particles or other such
effects, and colour either makes its appearance
or becomes changed .

THE FORCE OF COLOUR.

693.

The physical colours, and especially those of

the prism, were formerly called " colores em-
phatici," on account of their extraordinary

beauty and force. Strictly speaking, however,

a high degree of effect may be ascribed to all
appearances of colour, assuming that they are
exhibited under the purest and most perfect
conditions .
694 .

The dark nature of colour, its full rich quality,

is what produces the grave, and at the same
time fascinating impression we sometimes ex-
perience, and as colour is to be considered a
condition of light, so it cannot dispense with
light as the co- operating cause of its appear-
ance, as its basis or ground ; as a power thus
displaying and manifesting colour.
T 2
 276

THE DEFINITE NATURE OF COLOUR.

695.

The existence and the relatively definite cha

racter of colour are one and the same thing.
Light displays itself and the face of nature , as
it were, with a general indifference, informing
us as to surrounding objects perhaps devoid of
interest or importance ; but colour is at all times
specific , characteristic , significant.

696.

Considered in a general point of view, colour

is determined towards one of two sides . It thus

presents a contrast which we call a polarity,

and which we may fitly designate by the ex
pressions plus and minus.

Plus . Minus.

Yellow. Blue.
Action . Negation . *
Light. Shadow .

Brightness . Darkness .
Force . Weakness .
Warmth . Coldness .

Proximity. Distance.

Repulsion Attraction .
Affinity with acids . Affinity with alkalis .

* Wirkung, Beraubung ; the last would be more literally ren

dered privation. The author has already frequently made use of
the terms active and passive as equivalent to plus and minus. -T.
 277

COMBINATION OF THE TWO PRINCIPLES .

697.

If these specific, contrasted principles are

combined, the respective qualities do not there
fore destroy each other : for if in this intermix
ture the ingredients are so perfectly balanced that
neither is to be distinctly recognised , the union
again acquires a specific character ; it appears
as a quality by itself in which we no longer
think of combination . This union we call green .

698 .

Thus, if two opposite phenomena springing

from the same source do not destroy each other
when combined , but in their . union present a
third appreciable and pleasing appearance, this
result at once indicates their harmonious rela

tion . The more perfect result yet remains to be

adverted to .

AUGMENTATION TO RED.

699.

Blue and yellow do not admit of increased

intensity without presently exhibiting a new
appearance in addition to their own . Each

colour, in its lightest state, is a dark ; if con

densed it must become darker, but this effect no

sooner takes place than the hue assumes an

appearance which we designate by the word
reddish.
278 AUGMENTATION TO RED.

700.

This appearance still increases, so that when

the highest degree of intensity is attained it
predominates over the original hue . A powerful
impression of light leaves the sensation of red
on the retina. In the prismatic yellow- red

which springs directly from the yellow, we

hardly recognise the yellow.

701 .

This deepening takes place again by means of

colourless semi-transparent mediums , and here
we see the effect in its utmost purity and ex-
tent. Transparent fluids , coloured with any
given hues, in a series of glass -vessels , exhibit
it very strikingly. The augmentation is unre-
mittingly rapid and constant ; it is universal ,

and obtains in physiological as well as in phy-

sical and chemical colours.

JUNCTION OF THE TWO AUGMENTED EXTREMES .

702.

As the extremes of the simple contrast pro-

duce a beautiful and agreeable appearance by
their union, so the deepened extremes on being
united , will present a still more fascinating
colour ; indeed, it might naturally be expected
that we should here find the acme of the whole

phenomenon .
 COMPLETENESS THE RESULT OF VARIETY . 279

703.

And such is the fact, for pure red appears ; a

colour to which, from its excellence, we have
appropriated the term " purpur."

704.

There are various modes in which pure red

may appear. By bringing together the violet

edge and yellow- red border in prismatic experi-

ments, by continued augmentation in chemical
operations, and by the organic contrast in phy-
siological effects .
705.

As a pigment it cannot be produced by inter-

mixture or union, but only by arresting the hue
in substances chemically acted on , at the high
culminating point. Hence the painter is jus-
tified in assuming that there are three primitive
colours from which he combines all the others.

The natural philosopher, on the other hand,

assumes only two elementary colours, from which
he, in like manner, developes and combines the
rest.

COMPLETENESS THE RESULT OF VARIETY IN COLOUR.

706 .

The various appearances of colour arrested in

* Wherever this word occurs incidentally it is translated pure

red, the English word purple being generally employed to denote
a colour similar to violet.-T.
280 HARMONY OF THE COMPLETE STATE .

their different degrees, and seen in juxtaposi

tion, produce a whole . This totality is harmony
to the eye .
707 .
The chromatic circle has been gradually pre

sented to us ; the various relations of its pro

gression are apparent to us. Two pure original
principles in contrast, are the foundation of the

whole ; an augmentation manifests itself by

means of which both approach a third state ;
hence there exists on both sides a lowest and

highest, a simplest and most qualified state.

Again, two combinations present themselves ;
first that of the simple primitive contrasts, then
that of the deepened contrasts.

HARMONY OF THE COMPLETE STATE.

703.

The whole ingredients of the chromatic scale,

seen in juxtaposition , produce an harmonious
impression on the eye. The difference between

the physical contrast and harmonious opposition

in all its extent should not be overlooked . The

first resides in the pure restricted original dual

ism , considered in its antagonizing elements ;
the other results from the the fully developed
effects of the complete state .

709.
"
Every single opposition in order to be har
monious must comprehend the whole. The
 EVANESCENCE OF COLOUR. 281

physiological experiments are sufficiently con

vincing on this point. A development of all the
possible contrasts of the chromatic scale will be

shortly given.*

FACILITY WITH WHICH COLOUR MAY BE MADE TO TEND

EITHER TO THE PLUS OR MINUS SIDE.

710.
We have already had occasion to take notice
of the mutability of colour in considering its so
called augmentation and progressive variations
round the whole circle ; but the hues even pass
and repass from one side to the other, rapidly
and of necessity .

711 .

Physiological colours are different in appear

ance as they happen to fall on a dark or on a
light ground. In physical colours the combina

tion of the objective and subjective experiments

is very remarkable. The epoptical colours , it
appears, are contrasted according as the light
shines through or upon them. To what extent
the chemical colours may be changed by fire
and alkalis, has been sufficiently shown in its

proper place.
EVANESCENCE OF COLOUR.

712.

All that has been adverted to as subsequent

No diagram or table of this kind was ever given by the au

thor.-T.
282 PERMANENCE OF COLOUR.

to the rapid excitation and definition of colour,

immixture , augmentation , combination, separa-
tion, not forgetting the law of compensatory

harmony, all takes place with the greatest

rapidity and facility ; but with equal quickness
colour again altogether disappears .

713 .

The physiological appearances are in no wise

to be arrested ; the physical last only as long as
the external condition lasts ; even the chemical
colours have great mutability, they may be
made to pass and repass from one side to the
other by means of opposite re-agents, and may
even be annihilated altogether.

PERMANENCE OF COLOUR.
714.

The chemical colours afford evidence of very

great duration. Colours fixed in glass by

fusion, and by nature in gems, defy all time and

re-action .

715.

The art of dyeing again fixes colour very

powerfully. The hues of pigments which might

otherwise be easily rendered mutable by re-
agents, may be communicated to substances in
the greatest permanency by means of mordants.
 283

PART V.

RELATION TO OTHER PURSUITS - RELATION TO

PHILOSOPHY.

716.

THE investigator of nature cannot be required

to be a philosopher, but it is expected that he
should so far have attained the habit of philo

sophizing, as to distinguish himself essentially

from the world , in order to associate himself
with it again in a higher sense. He should

form to himself a method in accordance with

observation, but he should take heed not to re

duce observation to mere notion , to substitute
words for this notion , and to use and deal with
these words as if they were things . He should

be acquainted with the labours of philosophers ,

in order to follow up the phenomena which have
been the subject of his observation , into the
philosophic region .

717.

It cannot be required that the philosopher

should be a naturalist, and yet his co-operation
in physical researches is as necessary as it is
desirable. He needs not an acquaintance with
details for this , but only a clear view of those
conclusions where insulated facts meet.
284 RELATION TO PHILOSOPHY.

718 .

We have before ( 175 ) alluded to this im

portant consideration , and repeat it here where
it is in its place. The worst that can happen to

physical science as well as to many other kinds

of knowledge is, that men should treat a se
condary phenomenon as a primordial one, and
(since it is impossible to derive the original fact
from the secondary state) , seek to explain what
is in reality the cause by an effect made to
usurp its place. Hence arises an endless con
fusion, a mere verbiage, a constant endeavour to
seek and to find subterfuges whenever truth
presents itself and threatens to be overpowering.

719.

While the observer, the investigator of nature,

is thus dissatisfied in finding that the appear

ances he sees still contradict a received theory,

the philosopher can calmly continue to operate
in his abstract department on a false result, for
no result is so false but that it can be made to

appear valid, as form without substance, by

some means or other.

720.

If, on the other hand, the investigator of na

ture can attain to the knowledge of that which

we have called a primordial phenomenon, he is
safe ; and the philosopher with him . The inves
 RELATION TO PHILOSOPHY. 285

tigator of nature is safe, since he is persuaded

that he has here arrived at the limits of his

science, that he finds himself at the height of

experimental research ; a height whence he can
look back upon the details of observation in all
its steps , and forwards into, if he cannot enter,
the regions of theory . The philosopher is safe,
for he receives from the experimentalist an
ultimate fact, which, in his hands , now becomes
an elementary one. He now justly pays little
attention to appearances which are understood
to be secondary, whether he already finds them.
scientifically arranged , or whether they present
themselves to his casual observation scattered
and confused . Should he even be inclined to

go over this experimental ground himself, and

not be averse to examination in detail , he does

this conveniently, instead of lingering too long

in the consideration of secondary and inter
mediate circumstances, or hastily passing them
over without becoming accurately acquainted
with them .

721 .

To place the doctrine of colours nearer, in this

sense, within the philosopher's reach, was the
author's wish ; and although the execution of
his purpose, from various causes, does not cor

respond with his intention, he will still keep

this object in view in an intended recapitula
286 RELATION TO MATHEMATICS .

tion, as well as in the polemical and historical

portions of his work ; for he will have to return
to the consideration of this point hereafter, on
an occasion where it will be necessary to speak
with less reserve .

RELATION TO MATHEMATICS .

722 .

It may be expected that the investigator of

nature, who proposes to treat the science of

natural philosophy in its entire range , should

be a mathematician . In the middle ages, ma
thematics was the chief organ by means of
which men hoped to master the secrets of nature ,
and even now, geometry in certain departments
of physics , is justly considered of first import
ance.

723.

The author can boast of no attainments of

this kind , and on this account confines himself

to departments of science which are indepen

dent of geometry ; departments which in mo
dern times have been opened up far and wide.

724.

It will be universally allowed that mathema

tics, one of the noblest auxiliaries which can

be employed by man , has, in one point of view,

been of the greatest use to the physical sciences ;
but that, by a false application of its methods ,
 RELATION TO MATHEMATICS. 287

it has, in many respects, been prejudicial to

them, is also not to be denied ; we find it here
and there reluctantly admitted .

725.

The theory of colours , in particular , has suf-

fered much, and its progress has been incalcu-
lably retarded by having been mixed up with:
optics generally, a science which cannot dis-
pense with mathematics ; whereas the theory of
colours , in strictness , may be investigated quite

independently of optics.

726 .

But besides this there was an additional evil.

A great mathematician was possessed with an

entirely false notion on the physical origin of
colours ; yet, owing to his great authority as a
geometer, the mistakes which he committed as
an experimentalist long became sanctioned in

the eyes of a world ever fettered in prejudices .

727 .

The author of the present inquiry has endea-

voured throughout to keep the theory of colours
distinct from the mathematics, although there
are evidently certain points where the assistance
of geometry would be desirable. Had not the
unprejudiced mathematicians, with whom he
has had, or still has, the good fortune to be ac-
288 RELATION TO MATHEMATICS .

quainted, been prevented by other occupations

from making common cause with him, his work
would not have wanted some merit in this re-

spect . But this very want may be in the end ad-

vantageous, since it may now become the object
of the enlightened mathematician to ascertain
where the doctrine of colours is in need of his

aid, and how he can contribute the means at

his command with a view to the complete eluci-

dation of this branch of physics .

728 .

In general it were to be wished that the Ger-

mans, who render such good service to science,

while they adopt all that is good from other

nations , could by degrees accustom themselves
to work in concert . We live, it must be con-

fessed, in an age, the habits of which are directly

opposed to such a wish. Every one seeks, not
only to be original in his views, but to be inde-
pendent of the labours of others, or at least to

persuade himself that he is so, even in the course

of his life and occupation . It is very often re-

marked that men who undoubtedly have accom-

plished much, quote themselves only, their own
writings, journals, and compendiums ; whereas
it would be far more advantageous for the indi-
vidual, and for the world, if many were devoted
to a common pursuit . The conduct of our
neighbours the French is, in this respect, worthy
 TECHNICAL OPERATIONS OF THE DYER. 289

of imitation ; we have a pleasing instance in

Cuvier's preface to his " Tableau Elémentaire
de l'Histoire Naturelle des Animaux ."

729.

He who has observed science and its pro

gress with an unprejudiced eye, might even ask

whether it is desirable that so many occupa

tions and aims , though allied to each other,

should be united in one person, and whether it
would not be more suitable for the limited

powers of the human mind to distinguish , for

example, the investigator and inventor, from
him who employs and applies the result of ex
periment ? Astronomers , who devote themselves
to the observation of the heavens and the disco

very or enumeration of stars, have in modern

times formed, to a certain extent, a distinct
class from those who calculate the orbits , con
sider the universe in its connexion, and more

accurately define its laws. The history of the

doctrine of colours will often lead us back to
these considerations .

RELATION TO THE TECHNICAL OPERATIONS OF

THE DYER.

730.

If in our labours we have gone out of the

province of the mathematician, we have, on the
other hand, endeavoured to meet the practical
U
290 TECHNICAL OPERATIONS OF THE DYER.

views of the dyer ; and although the chapter

which treats of colour in a chemical point of
view is not the most complete and circumstan-
tial, yet in that portion , as well as in our general
observations respecting colour, the dyer will find
his views assisted far more than by the theory
hitherto in vogue, which failed to afford him
any assistance.

731 .

It is curious, in this view, to take a glance

at the works containing directions on the art of
dyeing . As the Catholic , on entering his tem-
ple, sprinkles himself with holy water, and after

bending the knee, proceeds perhaps to converse

with his friends on his affairs , without any espe-

cial devotion ; so all the treatises on dyeing

begin with a respectful allusion to the accre-
dited theory , without afterwards exhibiting a
single trace of any principle deduced from this
theory, or showing that it has thrown light on
any part of the art, or that it offers any useful
hints in furtherance of practical methods .

732 .

On the other hand , there are men who, after

having become thoroughly and experimentally
acquainted with the nature of dyes, have not
been able to reconcile their observations with

the received theory ; who have , in short, disco-

 RELATION TO PHYSIOLOGY AND PATHOLOGY. 291

vered its weak points, and sought for a general

view more consonant to nature and experience.
When we come to the names of Castel and
Gülich, in our historical review, we shall have
occasion to enter into this more fully, and an
opportunity will then present itself to show that
an assiduous experience in taking advantage of
every accident may, in fact, be said almost to
exhaust the knowledge of the province to which
it is confined . The high and complete result is
then submitted to the theorist, who, if he ex

amines facts with accuracy , and reasons with

candour, will find such materials eminently
useful as a basis for his conclusions . -Note A A.

RELATION TO PHYSIOLOGY AND PATHOLOGY.

733 .

If the phenomena adduced in the chapter

where colours were considered in a physiological

and pathological view are for the most part

generally known , still some new views, mixed
up with them , will not be unacceptable to the
physiologist . We especially hope to have given
him cause to be satisfied by classing certain
phenomena which stood alone, under analogous
facts, and thus, in some measure, to have pre
pared the way for his further investigations .

734.

The appendix on pathological colours , again,

U 2
292 RELATION TO NATURAL HISTORY .

is admitted to be scanty and unconnected . We

reflect, however, that Germany can boast of
men who are not only highly experienced in
this department, but are likewise so distin
guished for general cultivation , that it can cost
them but little to revise this portion, to com

plete what has been sketched , and at the same

time to connect it with the higher facts of
organisation .

RELATION TO NATURAL HISTORY .

735 .

If we may at all hope that natural history

will gradually be modified by the principle of
deducing the ordinary appearances of nature
from higher phenomena , the author believes he
may have given some hints and introductory
views bearing on this object also . As colour,
in its infinite variety, exhibits itself on the sur
face of living beings, it becomes an important
part of the outward indications, by means of
which we can discover what passes underneath.

736 .

In one point of view it is certainly not to be

too much relied on , on account of its indefinite

and mutable nature ; yet even this mutability,

inasmuch as it exhibits itself as a constant qua

lity, again becomes a criterion of a mutable

vitality ; and the author wishes nothing more

 RELATION TO GENERAL PHYSICS . 293

than that time may be granted him to develop

the results of his observations on this subject
more fully ; here they would not be in their

place.

RELATION TO GENERAL PHYSICS .

737.

The state in which general physics now is ,

appears, again, particularly favourable to our
labours ; for natural philosophy, owing to inde-
fatigable and variously directed research, has
gradually attained such eminence, that it ap-
pears not impossible to refer a boundless empi-
ricism to one centre .

738 .

Without referring to subjects which are too

far removed from our own province, we observe
that the formulæ under which the elementary
appearances of nature are expressed , altogether
tend in this direction ; and it is easy to see that
through this correspondence of expression , a
correspondence in meaning will necessarily be
soon arrived at.

739.

True observers of nature, however they may

differ in opinion in other respects, will agree
that all which presents itself as appearance, all

that we meet with as phenomenon , must either

294 RELATION TO GENERAL PHYSICS .

indicate an original division which is capable

of union, or an original unity which admits of
division, and that the phenomenon will present
itself accordingly. To divide the united, to
unite the divided, is the life of nature ; this is

the eternal systole and diastole, the eternal col

lapsion and expansion , the inspiration and
expiration of the world in which we live and
move .

740.

It is hardly necessary to observe that what we

here express as number and restrict to dualism
is to be understood in a higher sense ; the ap

pearance of a third, a fourth order of facts pro

gressively developing themselves is to be simi
larly understood ; but actual observation should,
above all, be the basis of all these expressions .

741 .

Iron is known to us as a peculiar substance,

different from other substances in its ordinary
state we look upon it as a mere material remark
able only on account of its fitness for various
uses and applications . How little, however, is
necessary to do away with the comparative insig
nificancy of this substance. A two -fold power is

called forth ,* which , while it tends again to a

Eine Entzweyung geht vor ; literally, a division takes place.

According to some, the two magnetic powers are previously in
the bar, and are then separated at the ends.-T.
 RELATION TO GENERAL PHYSICS . 295

state of union, and, as it were , seeks itself, ac

quires a kind of magical relation with its like,
and propagates this double property , which is
in fact but a principle of reunion , throughout
all bodies of the same kind . We here first ob

serve the mere substance , iron ; we see the divi

sion that takes place in it propagate itself and
disappear, and again easily become re- excited .
This, according to our mode of thinking , is a
primordial phenomenon in immediate relation
with its idea, and which acknowledges nothing
earthly beyond it.

742 .

Electricity is again peculiarly characterised .

As a mere quality we are unacquainted with it ;
for us it is a nothing, a zero, a mere point, which,
however, dwells in all apparent existences, and
at the same time is the point of origin whence,
on the slightest stimulus , a double appearance
presents itself, an appearance which only mani
fests itself to vanish . The conditions under

which this manifestation is excited are infinitely

varied, according to the nature of particular

bodies . From the rudest mechanical friction of

very different substances with one another, to

the mere contiguity of two entirely similar bo

dies, the phenomenon is present and stirring,

nay, striking and powerful, and so decided and

specific, that when we employ the terms or for

296 RELATION TO GENERAL PHYSICS .

mulæ polarity , plus and minus, for north and

south , for glass and resin , we do so justifiably
and in conformity with nature.

743.

This phenomenon , although it especially af-

fects the surface , is yet by no means superficial.

It influences the tendency or determination of

material qualities, and connects itself in imme-
diate co-operation with the important double
phenomenon which takes place so universally
in chemistry, -oxydation , and de- oxydation.

744.
To introduce and include the appearances of
colour in this series, this circle of phenomena

was the object of our labours . What we have

not succeeded in others will accomplish. We
found a primordial vast contrast between light
and darkness , which may be more generally
expressed by light and its absence . We looked
for the intermediate state, and sought by means

of it to compose the visible world of light,

shade, and colour. In the prosecution of this
we employed various terms applicable to the
development of the phenomena , terms which
we adopted from the theories of magnetism, of
electricity , and of chemistry. It was necessary,
however, to extend this terminology , since we
found ourselves in an abstract region , and had
to express more complicated relations.
 RELATION TO GENERAL PHYSICS . 297

745 .

If electricity and galvanism , in their general

character, are distinguished as superior to the
more limited exhibition of magnetic phenomena,

it may be said that colour, although coming

under similar laws, is still superior ; for since
it addresses itself to the noble sense of vision ,

its perfections are more generally displayed .

Compare the varied effects which result from

the augmentation of yellow and blue to red,

from the combination of these two higher ex-
tremes to pure red, and the union of the two
inferior extremes to green. What a far more
varied scheme is apparent here than that in
which magnetism and electricity are compre-
hended . These last phenomena may be said
to be inferior again on another account ; for
though they penetrate and give life to the uni-
verse, they cannot address themselves to man

in a higher sense in order to his employing

them æsthetically . The general , simple, phy-
sical law must first be elevated and diversified
itself in order to be available for elevated uses .

746 .

If the reader, in this spirit, recalls what has

been stated by us throughout, generally and in
detail, with regard to colour, he will himself
pursue and unfold what has been here only
lightly hinted at. He will augur well for
298 RELATION TO THE THEORY OF MUSIC.

science, technical processes , and art, if it should

prove possible to rescue the attractive subject
of the doctrine of colours from the atomic re-
striction and isolation in which it has been

banished, in order to restore it to the general

dynamic flow of life and action which the pre-
sent age loves to recognise in nature . These

considerations will press upon us more strongly

when , in the historical portion , we shall have to

speak of many an enterprising and intelligent
man who failed to possess his contemporaries
with his convictions .

RELATION TO THE THEORY OF MUSIC.

747.

Before we proceed to the moral associations

of colour, and the aesthetic influences arising
from them , we have here to say a few words on
its relation to melody . That a certain relation
exists between the two, has been always felt ;
this is proved by the frequent comparisons we
meet with , sometimes as passing allusions,
sometimes as circumstantial parallels . The
error which writers have fallen into in trying to
establish this analogy we would thus define :

748 .

Colour and sound do not admit of being di-

rectly compared together in any way, but both

are referable to a higher formula , both are de-
 RELATION TO THE THEORY OF MUSIC . 299

rivable, although each for itself, from this higher

law. They are like two rivers which have their
source in one and the same mountain , but sub-
sequently pursue their way under totally dif-
ferent conditions in two totally different regions ,
so that throughout the whole course of both no
two points can be compared . Both are general,
elementary effects acting according to the gene-
ral law of separation and tendency to union , of
undulation and oscillation , yet acting thus in
wholly different provinces, in different modes,
on different elementary mediums, for different
senses .-Note B B.

749 .

Could some investigator rightly adopt the

method in which we have connected the doc-
trine of colours with natural philosophy gene-

rally, and happily supply what has escaped or

been missed by us, the theory of sound , we are
persuaded, might be perfectly connected with
general physics : at present it stands, as it were,
isolated within the circle of science.

750.

It is true it would be an undertaking of the

greatest difficulty to do away with the positive
character which we are now accustomed to at-

tribute to music - a character resulting from the

achievements of practical skill , from accidental ,
300 CONCLUDING OBSERVATIONS ON TERMINOLOGY.

mathematical , aesthetical influences - and to

substitute for all this a merely physical inquiry
tending to resolve the science into its first ele
ments . Yet considering the point at which
science and art are now arrived , considering the
many excellent preparatory investigations that
have been made relative to this subject, we may

perhaps still see it accomplished .

CONCLUDING OBSERVATIONS ON TERMINOLOGY.

751 .

We never sufficiently reflect that a language,

strictly speaking, can only be symbolical and
figurative, that it can never express things di
rectly, but only, as it were, reflectedly. This
is especially the case in speaking of qualities
which are only imperfectly presented to obser
vation, which might rather be called powers
than objects , and which are ever in movement
throughout nature . They are not to be arrested,
and yet we find it necessary to describe them ;
hence we look for all kinds of formulæ in order,
figuratively at least, to define them .

752.

Metaphysical formulæ have breadth as well

as depth, but on this very account they require
a corresponding import ; the danger here is
vagueness . Mathematical expressions may in
many cases be very conveniently and happily
 CONCLUDING OBSERVATIONS ON TERMINOLOGY. 301

employed, but there is always an inflexibility

in them, and we presently feel their inadequacy ;
for even in elementary cases we are very soon
conscious of an incommensurable idea ; they

are, besides, only intelligible to those who are

especially conversant in the sciences to which
such formulæ are appropriated . The terms of
the science of mechanics are more addressed

to the ordinary mind, but they are ordinary in

other senses, and always have something unpo-
lished ; they destroy the inward life to offer
from without an insufficient substitute for it.
The formulæ of the corpuscular theories are
nearly allied to the last ; through them the mu-
table becomes rigid, description and expression
uncouth while , again , moral terms, which un-
doubtedly can express nicer relations , have the

effect of mere symbols in the end , and are in

danger of being lost in a play of wit.

753.

If, however, a writer could use all these

modes of description and expression with per-
fect command , and thus give forth the result of
his observations on the phenomena of nature
in a diversified language ; if he could preserve
himself from predilections, still embodying a
lively meaning in as animated an expression ,
we might look for much instruction communi-

cated in the most agreeable of forms.

302 CONCLUDING OBSERVATIONS ON TERMINOLOGY.

754.

Yet, how difficult it is to avoid substituting

the sign for the thing ; how difficult to keep the
essential quality still living before us, and not to
kill it with the word. With all this , we are ex

posed in modern times to a still greater danger

by adopting expressions and terminologies from
all branches of knowledge and science to em
body our views of simple nature. Astronomy,
cosmology, geology, natural history, nay religion
and mysticism , are called in in aid ; and how
often do we not find a general idea and an ele
mentary state rather hidden and obscured than
elucidated and brought nearer to us by the em
ployment of terms , the application of which is
strictly specific and secondary . We are quite
aware of the necessity which led to the intro
duction and general adoption of such a language,
we also know that it has become in a certain

sense indispensable ; but it is only a moderate,

unpretending recourse to it, with an internal

conviction of its fitness, that can recommend it.

755 .

After all , the most desirable principle would

be that writers should borrow the expressions
employed to describe the details of a given pro
vince of investigation from the province itself ;
treating the simplest phenomenon as an ele
 CONCLUDING OBSERVATIONS ON TERMINOLOGY. 303

mentary formula, and deriving and developing

the more complicated designations from this .

756 .

The necessity and suitableness of such a con-

ventional language where the elementary sign

expresses the appearance itself, has been duly

appreciated by extending, for instance, the ap-
plication of the term polarity, which is borrowed

from the magnet to electricity, & c . The plus

and minus which may be substituted for this ,
have found as suitable an application to many

phenomena ; even the musician , probably with-

out troubling himself about these other depart-
ments, has been naturally led to express the
leading difference in the modes of melody by
major and minor.

757.

For ourselves we have long wished to intro-

duce the term polarity into the doctrine of
colours ; with what right and in what sense, the
present work may show. Perhaps we may here-
after find room to connect the elementary phe-
nomena together according to our mode, by a
similar use of symbolical terms, terms which
must at all times convey the directly corres-
ponding idea ; we shall thus render more ex-
plicit what has been here only alluded to gene-
rally, and perhaps too vaguely expressed .
 304

PART VI .

EFFECT OF COLOUR WITH REFERENCE TO MORAL

ASSOCIATIONS.

758 .

SINCE colour occupies so important a place in

the series of elementary phenomena, filling as it
does the limited circle assigned to it with fullest
variety, we shall not be surprised to find that
its effects are at all times decided and significant,

and that they are immediately associated with

the emotions of the mind . We shall not be

surprised to find that these appearances pre

sented singly, are specific, that in combination
they may produce an harmonious , characteristic ,
often even an inharmonious effect on the eye ,

by means of which they act on the mind ; pro

ducing this impression in their most general ele
mentary character, without relation to the nature

or form of the object on whose surface they are

apparent. Hence , colour considered as an ele
ment of art, may be made subservient to the
highest æsthetical ends .- Note C C.

759.

People experience a great delight in colour,

generally. The eye requires it as much as it
requires light. We have only to remember the
 REFERENCE TO MORAL ASSOCIATIONS. 305

refreshing sensation we experience , if on a

cloudy day the sun illumines a single portion of
the scene before us and displays its colours .
That healing powers were ascribed to coloured
gems, may have arisen from the experience of
this indefinable pleasure .

760.

The colours which we see on objects are not

qualities entirely strange to the eye ; the organ

is not thus merely habituated to the impres
sion ; no, it is always predisposed to produce
colour of itself, and experiences a sensation of
delight if something analogous to its own nature
is offered to it from without ; if its susceptibility
is distinctly determined towards a given state .

761 .

From some of our earlier observations we can

conclude, that general impressions produced by

single colours cannot be changed , that they act
specifically, and must produce definite, specific
states in the living organ.

762 ..

They likewise produce a corresponding in

fluence on the mind . Experience teaches us
that particular colours excite particular states
of feeling. It is related of a witty Frenchman ,
" Il prétendoit que son ton de conversation avec
X
306 REFERENCE TO MORAL ASSOCIATIONS .

Madame étoit changé depuis qu'elle avoit

changé en cramoisi le meuble de son cabinet,
qui étoit bleu. "
763.

In order to experience these influences com

pletely, the eye should be entirely surrounded
with one colour ; we should be in a room of one

colour, or look through a coloured glass . We

are then identified with the hue , it attunes the
eye and mind in mere unison with itself.

764 .

The colours on the plus side are yellow, red

yellow ( orange ) , yellow-red (minium , cinnabar) .
The feelings they excite are quick, lively, as
piring.
YELLOW .
765.

This is the colour nearest the light. It ap

pears on the slightest mitigation of light, whe
ther by semi- transparent mediums or faint
reflection from white surfaces . In prismatic

experiments it extends itself alone and widely

in the light space , and while the two poles re
main separated from each other, before it mixes

with blue to produce green it is to be seen in its

utmost purity and beauty . How the chemical
yellow developes itself in and upon the white,
has been circumstantially described in its proper
place.
 YELLOW . 307

766.

In its highest purity it always carries with it

the nature of brightness, and has a serene, gay,
softly exciting character.

767.

In this state, applied to dress, hangings, car

peting, & c ., it is agreeable . Gold in its per

fectly unmixed state, especially when the effect

of polish is superadded , gives us a new and high
idea of this colour ; in like manner, a strong

yellow, as it appears on satin , has a magnificent

and noble effect .

768 .

We find from experience, again , that yellow ex

cites a warm and agreeable impression . Hence
in painting it belongs to the illumined and em
phatic side .

769.

This impression of warmth may be experi

enced in a very lively manner if we look at a
landscape through a yellow glass, particularly
on a grey winter's day. The eye is gladdened ,
the heart expanded and cheered , a glow seems
at once to breathe towards us .

770.

If, however, this colour in its pure and bright

x 2
308 YELLOW .

state is agreeable and gladdening , and in its

utmost power is serene and noble, it is, on the

other hand, extremely liable to contamination ,

and produces a very disagreeable effect if it is
sullied, or in some degree tends to the minus

side . Thus, the colour of sulphur, which inclines

to green , has a something unpleasant in it.

771 .

When a yellow colour is communicated to dull

and coarse surfaces, such as common cloth , felt,
or the like, on which it does not appear with
full energy, the disagreeable effect alluded to is

apparent. By a slight and scarcely perceptible

change, the beautiful impression of fire and gold
is transformed into one not undeserving the

epithet foul ; and the colour of honour and joy

reversed to that of ignominy and aversion . To
this impression the yellow hats of bankrupts
and the yellow circles on the mantles of Jews,
may have owed their origin .

RED-YELLOW.

772.

As no colour can be considered as stationary,

so we can very easily augment yellow into red
dish by condensing or darkening it. The colour
increases in energy, and appears in red - yellow
more powerful and splendid.
 RED-YELLOW. 309

773.

All that we have said of yellow is applicable

here in a higher degree . The red -yellow gives
an impression of warmth and gladness, since it
represents the hue of the intenser glow of fire,
and of the milder radiance of the setting sun.

Hence it is agreeable around us, and again, as

clothing, in greater or less degrees is cheerful
and magnificent. A slight tendency to red im
mediately gives a new character to yellow, and
while the English and Germans content them
selves with bright pale yellow colours in leather,
the French, as Castel has remarked , prefer a
yellow enhanced to red ; indeed, in general,
everything in colour is agreeable to them which
belongs to the active side.

YELLOW-RED.

774.

As pure yellow passes very easily to red

yellow, so the deepening of this last to yellow
red is not to be arrested . The agreeable ,

cheerful sensation which red-yellow excites , in

creases to an intolerably powerful impression in
bright yellow-red .

775.

The active side is here in its highest energy,

and it is not to be wondered at that impetuous,

robust, uneducated men, should be especially

310 YELLOW-RED.

pleased with this colour. Among savage nations

the inclination for it has been universally re

marked, and when children , left to themselves,

begin to use tints, they never spare vermilion
and minium .

776 .

In looking steadfastly at a perfectly yellow

red surface, the colour seems actually to pene
trate the organ . It produces an extreme ex

citement, and still acts thus when somewhat

darkened . A yellow-red cloth disturbs and

enrages animals. I have known men of educa

tion to whom its effect was intolerable if they

chanced to see a person dressed in a scarlet
cloak on a grey, cloudy day.

777.

The colours on the minus side are blue, red

blue, and blue - red . They produce a restless ,

susceptible, anxious impression .

BLUE.

778.

As yellow is always accompanied with light,

so it may be said that blue still brings a prin
ciple of darkness with it.

779.

This colour has a peculiar and almost inde

 BLUE. 311

scribable effect on the eye. As a hue it is power

ful , but it is on the negative side, and in its

highest purity is, as it were, a stimulating
negation. Its appearance , then, is a kind of
contradiction between excitement and repose.

780.

As the upper sky and distant mountains

appear blue, so a blue surface seems to retire
from us.

781 .

But as we readily follow an agreeable object

that flies from us, so we love to contemplate
blue, not because it advances to us , but because
it draws us after it.

782.

Blue gives us an impression of cold , and thus,

again, reminds us of shade. We have before
spoken of its affinity with black.

783.

Rooms which are hung with pure blue, appear

in some degree larger, but at the same time
empty and cold.

784 .

The appearance of objects seen through a

blue glass is gloomy and melancholy .
 312 RED-BLUE.

785.

When blue partakes in some degree of the

plus side, the effect is not disagreeable. Sea
green is rather a pleasing colour.

RED-BLUE.

786 .

We found yellow very soon tending to the in

tense state, and we observe the same progres
sion in blue.

787.

Blue deepens very mildly into red, and thus

acquires a somewhat active character, although
it is on the passive side. Its exciting power is,
however, of a very different kind from that of
the red-yellow . It may be said to disturb rather
than enliven .

788.

As augmentation itself is not to be arrested ,

so we feel an inclination to follow the progress
of the colour, not, however, as in the case of the
red- yellow, to see it still increase in the active
•
sense, but to find a point to rest in.

789.

In a very attenuated state, this colour is

known to us under the name of lilac ; but even

in this degree it has a something lively without

gladness.
 313

BLUE-RED.

790.

This unquiet feeling increases as the hue pro-

gresses, and it may be safely assumed, that a
carpet of a perfectly pure deep blue-red would
be intolerable. On this account, when it is used
for dress, ribbons, or other ornaments, it is em-
ployed in a very attenuated and light state, and
thus displays its character as above defined , in
a peculiarly attractive manner.

791 .

As the higher dignitaries of the church have

appropriated this unquiet colour to themselves ,
we may venture to say that it unceasingly as-
pires to the cardinal's red through the restless
degrees of a still impatient progression.

RED.

792.

We are here to forget everything that borders

on yellow or blue. We are to imagine an ab-
solutely pure red , like fine carmine suffered to
dry on white porcelain . We have called this
colour " purpur" by way of distinction , although

we are quite aware that the purple of the an-

cients inclined more to blue.

793.

Whoever is acquainted with the prismatic

314 RED.

origin of red , will not think it paradoxical if we

assert that this colour partly actu, partly po
tentiâ, includes all the other colours.

794.

We have remarked a constant progress or

augmentation in yellow and blue, and seen what

impressions were produced by the various states ;
hence it may naturally be inferred that now, in
the junction of the deepened extremes, a feeling
of satisfaction must succeed ; and thus, in phy
sical phenomena, this highest of all appearances
of colour arises from the junction of two con
trasted extremes which have gradually prepared
themselves for a union.

795.

As a pigment, on the other hand, it presents

itself to us already formed, and is most perfect
as a hue in cochineal ; a substance which , how

ever, by chemical action may be made to tend

to the plus or the minus side, and may be con
sidered to have attained the central point in the
best carmine .

796.

The effect of this colour is as peculiar as its

nature . It conveys an impression of gravity

and dignity, and at the same time of grace and

attractiveness . The first in its dark deep state,
 RED. 315

the latter in its light attenuated tint ; and thus

the dignity of age and the amiableness of youth
may adorn itself with degrees of the same hue.

797 .

History relates many instances of the jealousy

of sovereigns with regard to the quality of red .
Surrounding accompaniments of this colour
have always a grave and magnificent effect .

798.

The red glass exhibits a bright landscape in

so dreadful a hue as to inspire sentiments of awe.

799 .

Kermes and cochineal, the two materials

chiefly employed in dyeing to produce this

colour , incline more or less to the plus or minus
state, and may be made to pass and repass the

culminating point by the action of acids and

alkalis : it is to be observed that the French

arrest their operations on the active side, as is

proved by the French scarlet, which inclines to
yellow. The Italians, on the other hand , remain
on the passive side, for their scarlet has a tinge
of blue.
800.

By means of a similar alkaline treatment, the

so-called crimson is produced ; a colour which
the French must be particularly prejudiced
316 GREEN.

against, since they employ the expressions

" Sot en cramoisi , méchant en cramoisi, " to
mark the extreme of the silly and the repre
hensible.

GREEN.

801 .

If yellow and blue , which we consider as the

most fundamental and simple colours , are united
as they first appear, in the first state of their
action, the colour which we call green is the
result.
802.

The eye experiences a distinctly grateful im

pression from this colour. If the two elementary
colours are mixed in perfect equality so that
neither predominates , the eye and the mind re
pose on the result of this junction as upon a
simple colour. The beholder has neither the
wish nor the power to imagine a state beyond
it. Hence for rooms to live in constantly, the
green colour is most generally selected .

COMPLETENESS AND HARMONY.

803.

We have hitherto assumed, for the sake of

clearer explanation , that the eye can be com

pelled to assimilate or identify itself with a
single colour ; but this can only be possible for
an instant .
 COMPLETENESS AND HARMONY. 317

804.

For when we find ourselves surrounded by a

given colour which excites its corresponding
sensation on the eye, and compels us by its pre
sence to remain in a state identical with it, this
state is soon found to be forced, and the organ
unwillingly remains in it.

805.

When the eye sees a colour it is immediately

excited, and it is its nature , spontaneously and
of necessity, at once to produce another, which
with the original colour comprehends the whole
chromatic scale . A single colour excites , by a
specific sensation, the tendency to universality.

806 .

To experience this completeness, to satisfy

itself, the eye seeks for a colourless space next

every hue in order to produce the complemental

hue upon it.

807.

In this resides the fundamental law of all

harmony of colours , of which every one may

convince himself by making himself accurately
acquainted with the experiments which we have
described in the chapter on the physiological
colours .
318 COMPLETENESS AND HARMONY.

808.

If, again, the entire scale is presented to the

eye externally, the impression is gladdening,
since the result of its own operation is pre-

sented to it in reality. We turn our attention

therefore, in the first place, to this harmonious

juxtaposition.

809.

As a very simple means of comprehending

the principle of this , the reader has only to
imagine a moveable diametrical index in the
colorific circle . * The index , as it revolves round
the whole circle, indicates at its two extremes

the complemental colours, which , after all , may

be reduced to three contrasts .

810.

Yellow demands Red- blue,

Blue 99 Red-yellow,
Red Green ,
and contrariwise.

811 .

In proportion as one end of the supposed in-

dex deviates from the central intensity of the
colours , arranged as they are in the natural
order, so the opposite end changes its place in
the contrasted gradation , and by such a simple

* Plate 1 , fig. 3.
 COMPLETENESS AND HARMONY. 319

contrivance the complemental colours may be

indicated at any given point . A chromatic

circle might be made for this purpose, not con-

fined, like our own , to the leading colours , but
exhibiting them with their transitions in an un-
broken series . This would not be without its

use, for we are here considering a very import-

ant point which deserves all our attention .*

812 .

We before stated that the eye could be in

some degree pathologically affected by being
long confined to a single colour ; that, again ,
definite moral impressions were thus produced ,
at one time lively and aspiring, at another sus-
ceptible and anxious- now exalted to grand
associations, now reduced to ordinary ones . We
now observe that the demand for completeness ,
which is inherent in the organ, frees us from

this restraint ; the eye relieves itself by pro-

ducing the opposite of the single colour forced

upon it, and thus attains the entire impression

which is so satisfactory to it.

813.

Simple, therefore, as these strictly harmo-

nious contrasts are, as presented to us in the.
narrow circle, the hint is important, that nature
tends to emancipate the sense from confined

* See Note C.
320 COMPLETENESS AND HARMONY.

impressions by suggesting and producing the

whole, and that in this instance we have a na-
tural phenomenon immediately applicable to
æsthetic purposes .

814.

While, therefore, we may assert that the chro-

matic scale, as given by us, produces an agree-

able impression by its ingredient hues , we may

here remark that those have been mistaken who
have hitherto adduced the rainbow as an exam-

ple of the entire scale ; for the chief colour,

pure red, is deficient in it, and cannot be pro-

duced, since in this phenomenon , as well as in

the ordinary prismatic series, the yellow- red
and blue-red cannot attain to a union .

815 .

Nature perhaps exhibits no general pheno-

menon where the scale is in complete combi-
nation. By artificial experiments such an

appearance may be produced in its perfect

splendour. The mode, however, in which the
entire series is connected in a circle , is rendered

most intelligible by tints on paper, till after

much experience and practice, aided by due
susceptibility of the organ, we become penetrated
with the idea of this harmony, and feel it present
in our minds .
 321

CHARACTERISTIC COMBINATIONS .

816 .

Besides these pure, harmonious , self-deve

loped combinations, which always carry the
conditions of completeness with them, there are
others which may be arbitrarily produced , and
which may be most easily described by observ
ing that they are to be found in the colorific
circle, not by diameters, but by chords , in such
a manner that an intermediate colour is passed
over.

817.

We call these combinations characteristic be

cause they have all a certain significancy and

tend to excite a definite impression ; an impres

sion , however, which does not altogether satisfy,

inasmuch as every characteristic quality of ne
cessity presents itself only as a part of a whole,
with which it has a relation , but into which it
cannot be resolved .

818.

As we are acquainted with the impressions

produced by the colours singly as well as in
their harmonious relations , we may at once con

clude that the character of the arbitrary combi

nations will be very different from each other as
regards their significancy . We proceed to re
view them separately.
Y
322 YELLOW AND RED- BLUE AND RED .

YELLOW AND BLUE.

819.

This is the simplest of such combinations .

It may be said that it contains too little, for
since every trace of red is wanting in it, it is
defective as compared with the whole scale. In
this view it may be called poor, and as the two
contrasting elements are in their lowest state ,
may be said to be ordinary ; yet it is recom
mended by its proximity to green- in short, by
containing the ingredients of an ultimate state.

YELLOW AND RED.

820.

This is a somewhat preponderating combina

tion, but it has a serene and magnificent effect.
The two extremes of the active side are seen

together without conveying any idea of pro

gression from one to the other. As the result
of their combination in pigments is yellow-red ,
so they in some degree represent this colour.

BLUE ANd red.

821 .

The two ends of the passive side with the

excess of the upper end of the active side .
The effect of this juxtaposition approaches that
of the blue-red produced by their union .
 323

YELLOW-RED AND BLUE-RED.

822.

These, when placed together, as the deepened

extremes of both sides, have something exciting,
elevated they give us a presentiment of red,
which in physical experiments is produced by
their union .

823.

These four combinations have also the com-

mon quality of producing the intermediate co-

lour of our colorific circle by their union , a

union which actually takes place if they are

opposed to each other in small quantities and

seen from a distance. A surface covered with

narrow blue and yellow stripes appears green

at a certain distance .

824 .

If, again, the eye sees blue and yellow next

each other, it finds itself in a peculiar disposi-
tion to produce green without accomplishing it,
while it neither experiences a satisfactory sen-
sation in contemplating the detached colours,
nor an impression of completeness in the two .

825.

Thus it will be seen that it was not without

reason we called these combinations character-
istic ; the more so, since the character of each
Y2
324 COMBINATIONS NON-CHARACTERISTIC.

combination must have a relation to that of the

single colours of which it consists .

COMBINATIONS NON -CHARACTERISTIC .

826.

We now turn our attention to the last kind of

combinations . These are easily found in the

circle ; they are indicated by shorter chords , for
in this case we do not pass over an entire inter-
mediate colour, but only the transition from one
to the other.

827.

These combinations may justly be called non-

characteristic , inasmuch as the colours are too

nearly alike for their impression to be signifi-

cant. Yet most of these recommend themselves

to a certain degree, since they indicate a pro-

gressive state, though its relations can hardly
be appreciable .

828 .

Thus yellow and yellow-red, yellow- red and

red , blue and blue- red , blue-red and red, repre-
sent the nearest degrees of augmentation and
culmination, and in certain relations as to quan-

tity may produce no unpleasant effect.

829.

The juxtaposition of yellow and green has

 RELATION TO LIGHT AND DARK . 325

always something ordinary, but in a cheerful

sense ; blue and green , on the other hand, is

ordinary in a repulsive sense. Our good fore

fathers called these last fool's colours .

RELATION OF THE COMBINATIONS TO LIGHT

AND DARK.

830..

These combinations may be very much varied

by making both colours light or both dark , or
one light and the other dark ; in which modifi
cations , however, all that has been found true

in a general sense is applicable to each parti

cular case . With regard to the infinite variety

thus produced, we merely observe :

831 .

The colours of the active side placed next to

black gain in energy, those of the passive side
lose. The active conjoined with white and

brightness lose in strength, the passive gain in

cheerfulness . Red and green with black appear
dark and grave ; with white they appear gay.

832.

To this we may add that all colours may be

more or less broken or neutralised , may to a
certain degree be rendered nameless, and thus
combined partly together and partly with pure
colours ; but although the relations may thus
326 CONSIDERATIONS DERIVED FROM THE

be varied to infinity, still all that is applicable

with regard to the pure colours will be appli-
cable in these cases.

CONSIDERATIONS DERIVED FROM THE EVIDENCE

OF EXPERIENCE AND HISTORY .

833.

The principles of the harmony of colours

having been thus far defined, it may not be
irrelevant to review what has been adduced in

connexion with experience and historical ex-

amples.

834 .

The principles in question have been derived

from the constitution of our nature and the
constant relations which are found to obtain in

chromatic phenomena . In experience we find

much that is in conformity with these principles ,
and much that is opposed to them.

835.

Men in a state of nature , uncivilised nations,

children, have a great fondness for colours in
their utmost brightness , and especially for yel-
low-red : they are also pleased with the motley.
By this expression we understand the juxtapo-
sition of vivid colours without an harmonious

balance ; but if this balance is observed , through

instinct or accident, an agreeable effect may be
produced. I remember a Hessian officer, re-
 EVIDENCE OF EXPERIENCE AND HISTORY. 327

turned from America, who had painted his face

with the positive colours , in the manner of the
Indians ; a kind of completeness or due balance
was thus produced , the effect of which was not
disagreeable .

836.

The inhabitants of the south of Europe make

use of very brilliant colours for their dresses .
The circumstance of their procuring silk stuffs
at a cheap rate is favourable to this propen
sity. The women , especially, with their bright
coloured bodices and ribbons , are always in

harmony with the scenery, since they cannot

possibly surpass the splendour of the sky and
landscape .

837.

The history of dyeing teaches us that certain

technical conveniences and advantages have had
great influence on the costume of nations. We
find that the Germans wear blue very generally

because it is a permanent colour in cloth ; so in

many districts all the country people wear green
twill, because that material takes a green dye
well. If a traveller were to pay attention to
these circumstances, he might collect some
amusing and curious facts .

838 .

Colours, as connected with particular frames

328 CONSIDERATIONS DERIVED FROM THE

of mind, are again a consequence of peculiar

character and circumstances. Lively nations ,
the French for instance , love intense colours ,
especially on the active side ; sedate nations ,
like the English and Germans , wear straw
coloured or leather-coloured yellow accom
panied with dark blue . Nations aiming at
dignity of appearance, the Spaniards and Ita
lians for instance, suffer the red colour of their
mantles to incline to the passive side .

839.

In dress we associate the character of the

colour with the character of the person . We

may thus observe the relation of colours singly ,

and in combination, to the colour of the com
plexion , age, and station .

840.

The female sex in youth is attached to rose

colour and sea-green, in age to violet and dark

green . The fair- haired prefer violet, as opposed

to light yellow, the brunettes , blue, as opposed
to yellow- red, and all on good grounds. The
Roman emperors were extremely jealous with
regard to their purple. The robe of the Chinese
Emperor is orange embroidered with red ; his

attendants and the ministers of religion wear

citron -yellow.
 EVIDENCE OF EXPERIENCE AND HISTORY . 329

841 .

People of refinement have a disinclination to

colours. This may be owing partly to weakness
of sight, partly to the uncertainty of taste,
which readily takes refuge in absolute negation .
Women now appear almost universally in white
and men in black.

842.

An observation, very generally applicable,

may not be out of place here, namely, that

man, desirous as he is of being distinguished , is
quite as willing to be lost among his fellows .

843.

Black was intended to remind the Venetian

noblemen of republican equality .

844.

To what degree the cloudy sky of northern

climates may have gradually banished colour
may also admit of explanation .

845 .

The scale of positive colours is obviously soon

exhausted ; on the other hand, the neutral , sub
dued , so - called fashionable colours present infi
nitely varying degrees and shades, most of
which are not unpleasing .
330 ESTHETIC INFLUENCE.

846.

It is also to be remarked that ladies , in wear-

ing positive colours, are in danger of making a

complexion which may not be very bright still
less so, and thus to preserve a due balance with
such brilliant accompaniments, they are induced
to heighten their complexions artificially.

847 .

An amusing inquiry might be made which

would lead to a critique of uniforms, liveries,

cockades , and other distinctions , according to
hinted at.
the principles above hinted at. It might be
observed , generally, that such dresses and in-
signia should not be composed of harmonious
colours . Uniforms should be characteristic and

dignified ; liveries might be ordinary and strik-

ing to the eye. Examples both good and bad
would not be wanting, since the scale of colours
usually employed for such purposes is limited ,
and its varieties have been often enough tried . *

ESTHETIC INFLUENCE .

848 .

From the moral associations connected with

the appearance of colours, single or combined ,

their æsthetic influence may now be deduced

* Some early Italian writers, Sicillo, Occolti , Rinaldi, and

others, have treated this subject in connexion with the supposed
signification of colours .-T.
 CHIARO-SCURO. 331

for the artist. We shall touch the most essential

points to be attended to after first considering

the general condition of pictorial representa
tion, light and shade, with which the appearance
of colour is immediately connected .

CHIARO-SCURO .

849.

We apply the term chiaro- scuro (Helldunkel)

to the appearance of material objects when the
mere effect produced on them by light and
shade is considered .-Note D D.

850.

In a narrower sense a mass of shadow lighted

by reflexes is often thus designated ; but we
here use the expression in its first and more
general sense .

851 .

The separation of light and dark from all ap

pearance of colour is possible and necessary.
The artist will solve the mystery of imitation
sooner by first considering light and dark inde
pendently of colour, and making himself ac
quainted with it in its whole extent.

852.

Chiaro- scuro exhibits the substance as sub

stance, inasmuch as light and shade inform us

as to degrees of density.
 332 CHIARO-SCURO .

853 .
We have here to consider the highest light,
the middle tint, and the shadow, and in the last
the shadow of the object itself, the shadow it
casts on other objects, and the illumined shadow
or reflexion .

854.

The globe is well adapted for the general ex

emplification of the nature of chiaro- scuro, but
it is not altogether sufficient . The softened

unity of such complete rotundity tends to the

vapoury, and in order to serve as a principle for
effects of art, it should be composed of plane
surfaces, so as to define the gradations more .

855.
The Italians call this manner " il piazzoso ; "

in German it might be called " das Flächen

hafte."* If, therefore, the sphere is a perfect

example of natural chiaro- scuro, a polygon

would exhibit the artist-like treatment in which

all kinds of lights , half-lights, shadows, and

reflexions, would be appreciable . —Note E E.

856.

The bunch of grapes is recognised as a good

example of a picturesque completeness in chiaro
scuro, the more so as it is fitted, from its form ,
to represent a principal group ; but it is only

* The English technical expressions " flat " and " square"
have an association of mannerism. -T.
 CHIARO-SCURO . 333

available for the master who can see in it what

he has the power of producing.

857.

In order to make the first idea intelligible to

the beginner, (for it is difficult to consider it
abstractedly even in a polygon, ) we may take
a cube, the three sides of which that are seen
represent the light, the middle tint, and the
shadow in distinct order .

858.

To proceed again to the chiaro - scuro of a

more complicated figure, we might select the

example of an open book, which presents a
greater diversity .

859.

We find the antique statues of the best time

treated very much with reference to these effects.
The parts intended to receive the light are
wrought with simplicity, the portion originally
in shade is , on the other hand, in more distinct
surfaces to make them susceptible of a variety
of reflexions ; here the example of the polygon
will be remembered .- Note F F.

860.

The pictures of Herculaneum and the Aldo

brandini marriage are examples of antique
painting in the same style.
334 TENDENCY TO COLOUR.

861 .

Modern examples may be found in single

figures by Raphael, in entire works by Cor
reggio, and also by the Flemish masters, espe
cially Rubens .

TENDENCY TO COLOUR.

862.

A picture in black and white seldom makes

its appearance ; some works of Polidoro are

examples of this kind of art. Such works, in

asmuch as they can attain form and keeping ,
are estimable, but they have little attraction
for the eye, since their very existence supposes
a violent abstraction .

863.

If the artist abandons himself to his feeling,

colour presently announces itself. Black no

sooner inclines to blue than the eye demands

yellow, which the artist instinctively modifies,
and introduces partly pure in the light, partly
reddened and subdued as brown, in the reflexes ,

thus enlivening the whole.- Note G G.

864 .

All kinds of camayeu, or colour on similar

colour, end in the introduction either of a com
plemental contrast, or some variety of hue.
Thus, Polidoro in his black and white frescoes
 TENDENCY TO COLOUR. 335

sometimes introduced a yellow vase, or some

thing of the kind .

865.

In general it may be observed that men have

at all times instinctively striven after colour in
the practice of the art. We need only observe
daily, how soon amateurs proceed from colour
less to coloured materials . Paolo Uccello

painted coloured landscapes to colourless figures .

-Note H H.

866.

Even the sculpture of the ancients could not

be exempt from the influence of this propensity.
The Egyptians painted their bas - reliefs ; statues
had eyes of coloured stones. Porphyry dra
peries were added to marble heads and extremi
ties, and variegated stalactites were used for the
pedestals of busts . The Jesuits did not fail to
compose the statue of their S. Luigi , in Rome,
in this manner, and the most modern sculpture
distinguishes the flesh from the drapery by
staining the latter.

KEEPING .

867 .

If linear perspective displays the gradation of

objects in their apparent size as affected by dis
tance, aërial perspective shows us their grada
336 KEEPING.

tion in greater or less distinctness , as affected

by the same cause.
868 .

Although from the nature of the organ of

sight, we cannot see distant objects so distinctly

as nearer ones , yet aërial perspective is grounded
strictly on the important fact that all mediums

called transparent are in some degree dim .

869.

The atmosphere is thus always, more or less ,

semi-transparent. This quality is remarkable
in southern climates, even when the barometer

is high, the weather dry, and the sky cloudless ,

for a very pronounced gradation is observable
between objects but little removed from each
other.
870.

The appearance on a large scale is known to

every one ; the painter, however, sees or be

lieves he sees , the gradation in the slightest

varieties of distance . He exemplifies it practi

cally by making a distinction , for instance, in

the features of a face according to their relative

position as regards the plane of the picture.

The direction of the light is attended to in like
manner. This is considered to produce a gra

dation from side to side, while keeping has re

ference to depth, to the comparative distinctness

of near and distant things.

1
 337

COLOURING .

871 .

In proceeding to consider this subject, we

assume that the painter is generally acquainted
with our sketch of the theory of colours, and
that he has made himself well acquainted with
certain chapters and rubrics which especially
concern him . He will thus be enabled to make

use of theory as well as practice in recognising

the principles of effect in nature, and in em
ploying the means of art.

COLOUR IN GENERAL NATURE .

872.

The first indication of colour announces itself

in nature together with the gradations of aerial

perspective ; for aerial perspective is intimately

connected with the doctrine of semi - transparent

mediums. We see the sky, distant objects and

even comparatively near shadows, blue. At the
same moment, the illuminating and illuminated

objects appear yellow, gradually deepening to

red. In many cases the physiological sugges
tion of contrasts comes into the account, and

an entirely colourless landscape, by means of

these assisting and counteracting tendencies ,
appears to our eyes completely coloured .
Z
 338

COLOUR OF PARTICULAR OBJECTS .

873.

Local colours are composed of the general

elementary colours ; but these are determined

or specified according to the properties of sub

stances and surfaces on which they appear :
this specification is infinite.

874.

Thus , there is at once a great difference be

tween silk and wool similarly dyed . Every
kind of preparation and texture produces corre
sponding modifications . Roughness , smooth
ness , polish, all are to be considered .

875 .

It is therefore one of the pernicious prejudices

of art that the skilful painter must never attend
to the material of draperies , but always repre
sent, as it were, only abstract folds . Is not all
characteristic variety thus done away with, and
is the portrait of Leo X. less excellent because
velvet, satin , and moreen, are imitated in their
relative effect ?

876 .

In the productions of nature, colours appear

more or less modified, specified , even indivi

dualised this may be readily observed in mine

 COLOUR OF PARTICULAR OBJECTS. 339

rals and plants, in the feathers of birds and the

skins of beasts .
877.

The chief art of the painter is always to imi

tate the actual appearance of the definite hue ,

doing away with the recollection of the ele

mentary ingredients of colour. This difficulty

is in no instance greater than in the imitation
of the surface of the human figure .

878 .

The colour of flesh, as a whole, belongs to the

active side, yet the bluish of the passive side

mingles with it. The colour is altogether re
moved from the elementary state and neutralised
by organisation.
879.

To bring the colouring of general nature into

harmony with the colouring of a given object,
will perhaps be more attainable for the judicious
artist after the consideration of what has been

pointed out in the foregoing theory. For the

most fancifully beautiful and varied appear
ances may still be made true to the principles
of nature .

CHARACTERISTIC COLOURING .

880.

The combination of coloured objects , as well

as the colour of their ground, should depend on
z 2
340 CHARACTERISTIC COLOURING .

considerations which the artist pre- establishes

for himself. Here a reference to the effect of

colours singly or combined , on the feelings , is

especially necessary. On this account the

painter should possess himself with the idea of

the general dualism , as well as of particular

contrasts, not forgetting what has been adverted

to with regard to the qualities of colours .

881 .

The characteristic in colour may be compre-

hended under three leading rubrics , which we

here define as the powerful , the soft, and the
splendid .

882.

The first is produced by the preponderance of

the active side , the second by that of the passive
side, and the third by completeness , by the ex-
hibition of the whole chromatic scale in due
balance .

883 .

The powerful impression is attained by yellow,

yellow-red, and red , which last colour is to be
arrested on the plus side . But little violet and
blue, still less green , are admissible . The soft
effect is produced by blue, violet, and red, which
in this case is arrested on the minus side ; a
moderate addition of yellow and yellow-red , but
much green may be admitted .
 HARMONIOUS COLOURING . 341

884.

If it is proposed to produce both these effects

in their full significancy, the complemental

colours may be excluded to a minimum, and

only so much of them may be suffered to appear

as is indispensable to convey an impression of

completeness.

HARMONIOUS COLOURING.

885.

Although the two characteristic divisions as

above defined may in some sense be also called

harmonious , the harmonious effect, properly so
called , only takes place when all the colours are
exhibited together in due balance .

886.

In this way the splendid as well as the agree

able may be produced ; both of these, however,
have of necessity a certain generalised effect,
and in this sense may be considered the reverse
of the characteristic .

887.

This is the reason why the colouring of most

modern painters is without character, for, while
they follow their general instinctive feeling only,
the last result of such a tendency must be mere

completeness ; this , they more or less attain ,

but thus at the same time neglect the charac
342 HARMONIOUS COLOURING.

teristic impression which the subject might

demand .

888.

But if the principles before alluded to are

kept in view, it must be apparent that a distinct
style of colour may be adopted on safe grounds
for every subject. The application requires, it
is true, infinite modifications , which can only
succeed in the hands of genius.

GENUINE TONE.

889.

If the word tone, or rather tune, is to be still

borrowed in future from music, and applied to

colouring, it might be used in a better sense

than heretofore .

890.

For it would not be unreasonable to compare

a painting of powerful effect, with a piece of

music in a sharp key ; a painting of soft effect
with a piece of music in a flat key, while other
equivalents might be found for the modifications
of these two leading modes .

FALSE TONE.

891 .

The word tone has been hitherto understood

to mean a veil of a particular colour spread over

 FALSE TONE . 343

the whole picture ; it was generally yellow, for

the painter instinctively pushed the effect to
wards the powerful side.

892.

If we look at a picture through a yellow glass

it will appear in this tone. It is worth while to

make this experiment again and again , in order

to observe what takes place in such an opera

tion . It is a sort of artificial light, deepening,

and at the same time darkening the plus side,

and neutralising the minus side.

893.

This spurious tone is produced instinctively

through uncertainty as to the means of attain

ing a genuine effect ; so that instead of com

pleteness, monotony is the result.

WEAK COLOURING .

894 .

It is owing to the same uncertainty that the

colours are sometimes so much broken as to

have the effect of a grey camayeu, the handling

being at the same time as delicate as possible .

895.

The harmonious contrasts are often found to

be very happily felt in such pictures, but with

out spirit, owing to a dread of the motley.

 344

THE MOTLEY.

896.

A picture may easily become party- coloured

or motley, when the colours are placed next each
other in their full force , as it were only mechani
cally and according to uncertain impressions.

897.

If, on the other hand, weak colours are com

bined, even although they may be dissonant,
the effect , as a matter of course , is not striking .
The uncertainty of the artist is communicated
to the spectator, who , on his side , can neither

praise nor censure.

898.

It is also important to observe that the colours

may be disposed rightly in themselves, but that
a work may still appear motley, if they are
falsely arranged in relation to light and shade.

899.

This may the more easily occur as light and

shade are already defined in the drawing, and
are, as it were, comprehended in it, while the

colour still remains open to selection.

DREAD OF THEORY.

900.

A dread of, nay, a decided aversion for all

 ULTIMATE AIM-GROUNDS . 345

theoretical views respecting colour and every-

thing belonging to it, has been hitherto found to

exist among painters ; a prejudice for which ,

after all , they were not to be blamed ; for what
has been hitherto called theory was groundless ,
vacillating, and akin to empiricism . We hope

that our labours may tend to diminish this pre-

judice, and stimulate the artist practically to
prove and embody the principles that have been
explained.

ULTIMATE AIM.

901 .

But without a comprehensive view of the

whole of our theory, the ultimate object will not
be attained . Let the artist penetrate himself
with all that we have stated . It is only by

means of harmonious relations in light and

shade, in keeping, in true and characteristic
colouring, that a picture can be considered com-
plete, in the sense we have now learnt to attach
to the term .

GROUNDS .

902.

It was the practice of the earlier artists to

paint on light grounds . This ground consisted
of gypsum, and was thickly spread on linen or
panel , and then levigated . After the outline
was drawn, the subject was washed in with a
346 GROUNDS .

blackish or brownish colour. Pictures prepared

I
in this manner for colouring are still in exist-
ence, by Leonardo da Vinci, and Fra Bar-
tolomeo ; there are also several by Guido.-
Note I I.
903.

When the artist proceeded to colour, and had

to represent white draperies , he sometimes suf-
fered the ground to remain untouched. Titian
did this latterly when he had attained the
greatest certainty in practice, and could accom-
plish much with little labour. The whitish

ground was left as a middle tint, the shadows

painted in, and the high lights touched on.-

Note K K.
904.

In the process of colouring, the preparation

merely washed as it were underneath, was
always effective . A drapery, for example, was
painted with a transparent colour, the white
ground shone through it and gave the colour
life , so the parts previously prepared for sha-
dows exhibited the colour subdued, without
being mixed or sullied .

905.

This method had many advantages ; for the

painter had a light ground for the light portions
of his work and a dark ground for the shadowed

portions . The whole picture was prepared ; the

 GROUNDS . 347

artist could work with thin colours in the sha

dows, and had always an internal light to give

value to his tints . In our own time painting in
water colours depends on the same principles.

906.

Indeed a light ground is now generally em

ployed in oil-painting, because middle tints
are thus found to be more transparent, and are

in some degree enlivened by a bright ground ;

the shadows , again , do not so easily become
black .

907 .

It was the practice for a time to paint on

dark grounds. Tintoret probably introduced
them . Titian's best pictures are not painted on
a dark ground.

908 .

The ground in question was red-brown, and

when the subject was drawn upon it, the
strongest shadows were laid in ; the colours of

the lights impasted very thickly in the bright

parts , and scumbled towards the shadows, so
that the dark ground appeared through the thin
colour as a middle tint. Effect was attained in

finishing by frequently going over the bright

parts and touching on the high lights.
348 GROUNDS .

909.

If this method especially recommended itself

in practice on account of the rapidity it allowed
of, yet it had pernicious consequences. The
strong ground increased and became darker,
and the light colours losing their brightness by
degrees, gave the shadowed portions more and
more preponderance . The middle tints became
darker and darker, and the shadows at last quite
obscure. The strongly impasted lights alone
remained bright, and we now see only light

spots on the painting . The pictures of the

Bolognese school , and of Caravaggio, afford
sufficient examples of these results .

910.

We may here in conclusion observe, that

glazing derives its effect from treating the pre
pared colour underneath as a light ground. By
this operation colours may have the effect of
being mixed to the eye, may be enhanced , and
may acquire what is called tone ; but they thus
necessarily become darker.

PIGMENTS .

911 .

We receive these from the hands of the che

mist and the investigator of nature . Much has

been recorded respecting colouring substances ,
 PIGMENTS. 349

which is familiar to all by means of the press .

But such directions require to be revised from

time to time . The master meanwhile communi

cates his experience in these matters to his

scholar, and artists generally to each other.

912 .

Those pigments which according to their

nature are the most permanent, are naturally
much sought after, but the mode of employing
them also contributes much to the duration of a

picture . The fewest possible colouring mate

rials are to be employed, and the simplest me
thods of using them cannot be sufficiently re
commended .

913.

For from the multitude of pigments colour

ing has suffered much. Every pigment has its

peculiar nature as regards its effect on the eye ;

besides this it has its peculiar quality, requiring

a corresponding technical method in its appli

cation . The former circumstance is a reason

why harmony is more difficult of attainment

with many materials than with few, the latter,

why chemical action and re- action may take
place among the colouring substances .

914.

We may refer, besides, to some false ten

350 PIGMENTS .

dencies which the artists suffer themselves to

be led away with . Painters are always looking

for new colouring substances, and believe when
such a substance is discovered that they have
made an advance in the art. They have a great

curiosity to know the practical methods of the

old masters , and lose much time in the search.
Towards the end of the last century we were

thus long tormented with wax-painting. Others

turn their attention to the discovery of new
methods, through which nothing new is accom

plished ; for, after all, it is the feeling of the

artist only that informs every kind of technical
process .

ALLEGORICAL, SYMBOLICAL, MYSTICAL APPLICATION

OF COLOUR.

915 .

It has been circumstantially shown above,

that every colour produces a distinct impression
on the mind, and thus addresses at once the eye
and feelings . Hence it follows that colour may
be employed for certain moral and æsthetic ends.

916.

Such an application , coinciding entirely with

nature, might be called symbolical , since the
colour would be employed in conformity with
its effect, and would at once express its mean
ing. If, for example , pure red were assumed to
 ALLEGORICAL APPLICATION OF COLOUR. 351

designate majesty, there can be no doubt that

this would be admitted to be a just and expres

sive symbol . All this has been already suffi

ciently entered into .

917 .

Another application is nearly allied to this ;

it might be called the allegorical applica
tion . In this there is more of accident and

caprice, inasmuch as the meaning of the sign

must be first communicated to us before we

know what it is to signify ; what idea, for in

stance, is attached to the green colour, which
has been appropriated to hope ?

918.

That, lastly, colour may have a mystical al

lusion, may be readily surmised , for since every
diagram in which the variety of colours may be
represented points to those primordial relations
which belong both to nature and the organ of

vision, there can be no doubt that these may be

made use of as a language, in cases where it is
proposed to express similar primordial relations
which do not present themselves to the senses
The ma
in so powerful and varied a manner.
thematician extols the value and applicability

of the triangle ; the triangle is revered by the

mystic ; much admits of being expressed in it
by diagrams, and, among other things, the law
352 ALLEGORICAL APPLICATION OF COLOUR.

of the phenomena of colours ; in this case, in-

deed, we presently arrive at the ancient myste-
rious hexagon .

919 .

When the distinction of yellow and blue is

duly comprehended , and especially the augmen-
tation into red , by means of which the opposite

qualities tend towards each other and become

united in a third ; then , certainly, an especially

mysterious interpretation will suggest itself,

since a spiritual meaning may be connected
with these facts ; and when we find the two se-

parate principles producing green on the one

hand and red in their intenser state, we can

hardly refrain from thinking in the first case on

the earthly, in the last on the heavenly , genera-
tion of the Elohim.-Note L L.

920.

But we shall do better not to expose our-

selves, in conclusion , to the suspicion of enthu-

siasm ; since, if our doctrine of colours finds

favour, applications and allusions , allegorical,

symbolical , and mystical, will not fail to be
made, in conformity with the spirit of the age .

CONCLUDING OBSERVATIONS .

In reviewing this labour, which has occupied

me long, and which at last I give but as a
 CONCLUDING OBSERVATIONS . 353

sketch, I am reminded of a wish once expressed

by a careful writer, who observed that he would
gladly see his works printed at once as he con-
ceived them, in order then to go to the task with
a fresh eye ; since everything defective presents
itself to us more obviously in print than even in
the cleanest manuscript. This feeling may be

imagined to be stronger in my case, since I had

not even an opportunity of going through a fair
transcript of my work before its publication ,
these pages having been put together at a time
when a quiet, collected state of mind was out of
the question . *

Some of the explanations I was desirous of

giving are to be found in the introduction , but
in the portion of my work to be devoted to the
history of the doctrine of colours , I hope to give
a more detailed account of my investigations
and the vicissitudes they underwent. One in-
quiry, however, may not be out of place here ;
the consideration , namely, of the question , what
can a man accomplish who cannot devote his

whole life to scientific pursuits ? what can he

perform as a temporary guest on an estate not
his own, for the advantage of the proprietor ?
When we consider art in its higher character,
we might wish that masters only had to do with

* Towards the close of 1806, when Weimar was occupied by

Napoleon after the battle of Jena.-T.
2 A
354 CONCLUDING OBSERVATIONS .

it, that scholars should be trained by the se

verest study, that amateurs might feel them

selves happy in reverentially approaching its

precincts . For a work of art should be the

effusion of genius, the artist should evoke its

substance and form from his inmost being, treat

his materials with sovereign command , and

make use of external influences only to accom
plish his powers .
But if the professor in this case has many
reasons for respecting the dilettante , the man of
science has every motive to be still more indul
gent, since the amateur here is capable of con
tributing what may be satisfactory and useful .
The sciences depend much more on experiment
than art, and for mere experiment many a vo
tary is qualified . Scientific results are arrived
at by many means, and cannot dispense with
many hands , many heads. Science may be
communicated, the treasure may be inherited ,
and what is acquired by one may be appropri
ated by many. Hence no one perhaps ought
to be reluctant to offer his contributions . How
much do we not owe to accident, to mere prac

tice, to momentary observation . All who are

endowed only with habits of attention, women,

children, are capable of communicating striking

and true remarks .

In science it cannot therefore be required ,

that he who endeavours to furnish something in
 CONCLUDING OBSERVATIONS . 355

its aid should devote his whole life to it , should

survey and investigate it in all its extent ; for
this, in most cases , would be a severe condition
even for the initiated. But if we look through
the history of science in general , especially the
history of physics , we shall find that many im-
portant acquisitions have been made by single
inquirers, in single departments , and very often
by unprofessional observers.
To whatever direction a man may be deter-
mined by inclination or accident, whatever
class of phenomena especially strike him, excite
his interest, fix his attention , and occupy him,
the result will still be for the advantage of
science for every new relation that comes to
light, every new mode of investigation , even the
imperfect attempt, even error itself is available ;
it may stimulate other observers and is never
without its use as influencing future inquiry.
With this feeling the author himself may look

back without regret on his endeavours . From

this consideration he can derive some encou-

ragement for the prosecution of the remainder

of his task ; and although not satisfied with the
result of his efforts , yet re- assured by the sin-
cerity of his intentions, he ventures to recom-
mend his past and future labours to the interest
of his contemporaries and posterity.

Multi pertransibunt et augebitur scientia.

2A2
I
 NOTES .

NOTE A.- Par. 18.

LEONARDO DA VINCI observes that " a light object relieved

on a dark ground appears magnified ;" and again, " Objects
seen at a distance appear out of proportion ; this is because
the light parts transmit their rays to the eye more powerfully
than the dark. A woman's white head-dress once appeared
to me much wider than her shoulders, owing to their being
dressed in black." * " It is now generally admitted that the
excitation produced by light is propagated on the retina a
little beyond the outline of the image. Professor Plateau,
of Ghent, has devoted a very interesting special memoir to
the description and explanation of phenomena of this nature.
See his Mémoire sur l'Irradiation, ' published in the 11th
vol . of the Transactions of the Royal Academy of Sciences
at Brussels." - S. F.

NOTE B.- Par. 23.

" The duration of ocular spectra produced by strongly

exciting the retina, may be conveniently measured by
minutes and seconds ; but to ascertain the duration of more
evanescent phenomena, recourse must be had to other
means. The Chevalier d'Arcy (Mem . de l'Acad . des Sc.

" Trattato della Pittura, Roma, 1817," p. 143-223 . This edition, pub-
lished from a Vatican MS., contains many observations not included in
former editions.
A few notes (marked with inverted commas and with the signature S. F.)
have been kindly furnished by a scientific friend.
358 NOTES .

1765, ) endeavoured to ascertain the duration of the impres

sion produced by a glowing coal in the following manner.
He attached it to the circumference of a wheel , the velocity
of which was gradually increased until the apparent trace of
the object formed a complete circle, and then measured the
duration of a revolution , which was obviously that of the
impression. To ascertain the duration of a revolution it is
sufficient merely to know the number of revolutions described
in a given time. Recently more refined experiments of the
same kind have been made by Professors Plateau and
Wheatstone."- S. F.

NOTE C.- Par. 50.

Every treatise on the harmonious combination of colours

contains the diagram of the chromatic circle more or less
elaborately constructed. These diagrams, if intended to
exhibit the contrasts produced by the action and re-action of
the retina, have one common defect. The opposite colours
are made equal in intensity ; whereas the complemental
colour pictured on the retina is always less vivid, and always
darker or lighter than the original colour . This variety un
doubtedly accords more with harmonious effects in painting.
The opposition of two pure hues of equal intensity, dif
fering only in the abstract quality of colour, would imme
diately be pronounced crude and inharmonious. It would
not, however, be strictly correct to say that such a contrast
is too violent ; on the contrary, it appears the contrast is not
carried far enough, for though differing in colour, the two
hues may be exactly similar in purity and intensity. Com
plete contrast, on the other hand, supposes dissimilarity in
all respects .
In addition to the mere difference of hue, the eye, it
seems, requires difference in the lightness or darkness of the
hue. The spectrum of a colour relieved as a dark on a
light ground, is a light colour on a dark ground , and vice
versa. Thus, if we look at a bright red wafer on the whitest
 NOTES . 359

surface, the complemental image will be still lighter than

the white surface ; if the same wafer is placed on a black
surface, the complemental image will be still darker. The
colour of both these spectra may be called greenish, but it
is evident that a colour must be scarcely appreciable as such,
if it is lighter than white and darker than black. It is,
however, to be remarked , that the white surface round the
light greenish image seems tinged with a reddish hue, and
the black surface round the dark image becomes slightly
illuminated with the same colour, thus in both cases assist
ing to render the image apparent (58) .
The difficulty or impossibility of describing degrees of
colour in words, has also had a tendency to mislead, by con
veying the idea of more positive hues than the physiological
contrast warrants. Thus, supposing scarlet to be relieved
as a dark, the complemental colour is so light in degree and
so faint in colour, that it should be called a pearly grey ;
whereas the theorists, looking at the quality of colour ab
stractedly, would call it a green- blue, and the diagram
would falsely present such a hue equal in intensity to scarlet,
or as nearly equal as possible.
Even the difference of mass which good taste requires
may be suggested by the physiological phenomena, for unless
the complemental image is suffered to fall on a surface pre
cisely as near to the eye as that on which the original colour
was displayed, it appears larger or smaller than the original
object (22) , and this in a rapidly increasing proportion.
Lastly, the shape itself soon becomes changed (26) .
That vivid colour demands the comparative absence of
colour, either on a lighter or darker scale, as its contrast,
may be inferred again from the fact that bright colourless
objects produce strongly coloured spectra. In darkness,
the spectrum which is first white, or nearly white, is fol
lowed by red in light, the spectrum which is first black, is
followed by green (39-44) . All colour, as the author ob
serves (259) , is to be considered as half-light, inasmuch as it
 360 NOTES .

is in every case lighter than black and darker than white.

Hence no contrast of colour with colour, or even of colour
with black or white , can be so great (as regards lightness or
darkness) as the contrast of black and white, or light and
dark abstractedly. This distinction between the differences
of degree and the differences of kind is important, since a
just application of contrast in colour may be counteracted
by an undue difference in lightness or darkness. The mere
contrast of colour is happily employed in some of Guido's
lighter pictures, but if intense darks had been opposed to his
delicate carnations, their comparative whiteness would have
been unpleasantly apparent. On the other hand, the flesh
colour in Giorgione, Sebastian del Piombo (his best imi
tator), and Titian, was sometimes so extremely glowing* that
the deepest colours, and black, were indispensable accom
paniments. The manner of Titian as distinguished from
his imitation of Giorgione, is golden rather than fiery, and
his biographers are quite correct in saying that he was fond
of opposing red (lake) and blue to his flesh . The cor
respondence of these contrasts with the physiological phe
nomena will be immediately apparent, while the occasional
practice of Rubens in opposing bright red to a still cooler
flesh-colour, will be seen to be equally consistent.
The effect of white drapery (the comparative absence of
colour) in enhancing the glow of Titian's flesh- colour, has
been frequently pointed out : the shadows of white thus
opposed to flesh, often present, again, the physiological con
trast, however delicately, according to the hue of the carna

" Ardito veramente alquanto, sanguigno, e quasi fiammeggiante."

-Zanetti della Pittura Veneziana, Ven. 1771 , p . 90. Warm as the flesh
colour of the colourists is, it still never approaches a positive hue, if we except
some examples in frescoes and other works intended to be seen at a great
distance. Zanetti, speaking of a fresco by Giorgione, now almost obliterated,
compares the colour to " un vivo raggio di cocente sole."-Varie Pitture a
fresco dei Principali Maestri Veneziani. Ven. 1760.
+ Ridolfi.
Zanetti , l. ii.
 NOTES . 361

tion. The lights, on the other hand, are not, and probably
never were, quite white, but from the first, partook of the
quality of depth, a quality assumed by the colourists to per
vade every part of a picture more or less.*
It was before observed that the description of colours in
words may often convey ideas of too positive a nature, and it
may be remarked generally that the colours employed by
the great masters are, in their ultimate effect, more or less
subdued or broken. The physiological contrasts are, how
ever, still applicable in the most comparatively neutral
scale.
Again, the works of the colourists show that these oppo
sitions are not confined to large masses (except perhaps in
works to be seen only at a great distance) ; on the contrary,
they are more or less apparent in every part, and when at
last the direct and intentional operations of the artist may
have been insufficient to produce them in their minuter
degrees , the accidental results of glazing and other methods
may be said to extend the contrasts to infinity. In such
productions, where every smallest portion is an epitome of
the whole, the eye still appreciates the fascinating effect of
contrast, and the work is pronounced to be true and com
plete, in the best sense of the words .
The Venetian method of scumbling and glazing exhibits
these minuter contrasts within each other, and is thus gene
rally considered more refined than the system of breaking
the colours , since it ensures a fuller gradation of hues , and
produces another class of contrasts, those, namely, which re
sult from degrees of transparence and opacity. In some of
the Flemish and Dutch masters, and sometimes in Reynolds,
the two methods are combined in great perfection .

* Two great authorities, divided by more than three centuries, Leon Bat
tista Alberti and Reynolds, have recommended this subdued treatment of
white. " It is to be remembered ," says the first, " that no surface should be
made so white that it cannot be made more so. In white dresses again, it
is necessary to stop far short of the last degree of whiteness."-Della Pittura,
1. ii., compare with Reynolds, vol . i , dis . 8 .
362 NOTES .

The chromatic diagram does not appear to be older than

the last century. It is one of those happy adaptations of
exacter principles to the objects of taste which might have
been expected from Leonardo da Vinci. That its true
principle was duly felt is abundantly evident from the works
of the colourists, as well as from the general observations
of early writers.* The more practical directions occasion
ally to be met with in the treatises of Leon Battista Alberti,
Leonardo da Vinci and others, are conformable to the
same system. Some Italian works, not written by painters,
which pretend to describe this harmony, are, however, very
imperfect. A passage in Lodovico Dolce's Dialogue on
Colours is perhaps the only one worth quoting. " He, "
says that writer, " who wishes to combine colours that are
agreeable to the eye, will put grey next dusky orange ; yel
low-green next rose-colour ; blue next orange ; dark purple,
black, next dark-green ; white next black, and white next
flesh-colour." The Dialogue on Painting, by the same
author, has the reputation of containing some of Titian's
precepts : if the above passage may be traced to the same
source, it must be confessed that it is almost the only one of
the kind in the treatise from which it is taken.

NOTE D.- Par. 66.

In some of these cases there can be no doubt that Goethe

* Vasari observes, " L'unione nella pittura è una discordanza di colori

diversi accordati insième. ” —Vol . i . c. 18. This observation is repeated by
various writers on art in nearly the same words, and at last appears in San
drart : " Concordia, potissimum picturæ decus , in discordiâ consistit, et quasi
litigio colorum ."- P. i. c . 5. The source, perhaps, is Aristotle : he observes,
"We are delighted with harmony, because it is the union of contrary princi
ples having a ratio to each other." - Problem.
+ See " Occolti Trattato de' Colori." Parma, 1568.
" Volendo l'uomo accoppiare insième colori che all'occhio dilettino
porrà insième il berrettino col leonato ; il verde-giallo con l'incarnato e rosso ;
il turchino con l'arangi ; il morello col verde oscuro ; il nero col bianco ; il
bianco con l'incarnato ."-Dialogo di M. Lodovico Dolce nel quale si ragiona
della qualità, diversità, e proprietà de' colori. Venezia, 1565 .
 NOTES. 363

attributes the contrast too exclusively to the physiological

cause, without making sufficient allowance for the actual
difference in the colour of the lights. The purely physical
nature of some coloured shadows was pointed out by Pohl
mann ; and Dr. Eckermann took some pains to convince
Goethe of the necessity of making such a distinction.
-Goethe at first adhered to his extreme view, but some time
afterwards confessed to Dr. Eckermann, that in the case of
the blue shadows of snow (74) , the reflection of the sky
was undoubtedly to be taken into the account. " Both
causes may, however, operate together," he observed, " and
the contrast which a warm yellow light demands may
heighten the effect of the blue." This was all his opponent
contended . *
With a few such exceptions, the general theory of Goethe
with regard to coloured shadows is undoubtedly correct ;
the experiments with two candles (68 ) , and with coloured
glass and fluids ( 80) , as well as the observations on the
shadows of snow ( 75) , are conclusive, for in all these cases
only one light is actually changed in colour, while the other
still assumes the complemental hue. " Coloured shadows,"
Dr. J. Müller observes, " are usually ascribed to the phy
siological influence of contrast ; the complementary colour
presented by the shadow being regarded as the effect of
internal causes acting on that part of the retina , and not of
the impression of coloured rays from without. This expla
nation is the one adopted by Rumford, Goethe, Grotthuss,
Brandes, Tourtual, Pohlmann, and most authors who have
studied the subject ."†
In the Historical Part the author gives an account of a
scarce French work, " Observations sur les Ombres Colo
rées, " Paris, 1782. The writer concludes that " the colour

* Eckermann's " Gespräche mit Goethe,” vol . ii . p. 76 and 280.

" Elements of Physiology," by J. Müller, M.D. , translated from the Ger
man by William Baly, M.D. London, 1839.
Anonymous, having only given the initials H. F. T.
364 NOTES .

of shadows is as much owing to the light that causes them

as to that which (more faintly) illumines them."

NOTE E.- Par. 69.

This opinion of the author is frequently repeated (201 ,

312, 591 ) , and as it seems at first sight to be at variance
with a received principle of art, it may be as well at once to
examine it.
In order to see the general proposition in its true point
of view, it will be necessary to forget the arbitrary distinc
tions of light and shade, and to consider all such modifica
tions between highest brightness and absolute darkness only
as so many lesser degrees of light.* The author, indeed,
by the word shadow, always understands a lesser light.
The received notion , as stated by Du Fresnoy, † is much
too positive and unconditional, and is only true when we
understand the " displaying" light to comprehend certain
degrees of half or reflected light, and the " destroying"
shade to mean the intensest degree of obscurity.
There are degrees of brightness which destroy colour as
well as degrees of darkness. In general, colour resides in
a mitigated light, but a very little observation shows us that
different colours require different degrees of light to display
them. Leonardo da Vinci frequently inculcates the general
principle above alluded to, but he as frequently qualifies it ;
for he not only remarks that the highest light may be com

* Leonardo da Vinci observes : " L'ombra è diminuzione di luce, tenebre è

privazione di luce." And again : " Sempre il minor lume è ombra del lume
maggiore." -Trattato della Pittura, pp. 274-299.
N. B. The same edition before described has been consulted throughout.
" Lux varium vivumque dabit, nullum umbra colorem."
De Arte Graphicâ .
" Know first that light displays and shade destroys
Refulgent nature's variegated dies ." -MASON's Translation .
A Spanish writer, Diego de Carvalho e Sampayo, quoted by Goethe (“ Far
benlehre," vol. ii .) , has a similar observation . This destroying effect of light
is striking in climates where the sun is powerful , and was not likely to escape
the notice of a Spaniard.
 NOTES. 365

parative privation of colour, but observes, with great truth,

that some hues are best displayed in their fully illumined
parts, some in their reflections, and some in their half
lights ; and again, that every colour is most beautiful when
lit by reflections from its own surface, or from a hue similar
to its own.*
The Venetians went further than Leonardo in this view
and practice ; and he seems to allude to them when he cri
ticises certain painters, who, in aiming at clearness and
fulness of colour, neglected what, in his eyes, was of supe
rior importance, namely, gradation and force of chiaro
scuro.+
That increase of colour supposes increase of darkness, as
so often stated by Goethe, may be granted without difficulty.
To what extent, on the other hand, increase of darkness, or
rather diminution of light, is accompanied by increase of
colour, is a question which has been variously answered by
various schools. Examples of the total negation of the
principle are not wanting, nor are they confined to the in
fancy of the art. Instances, again, of the opposite tendency
are frequent in Venetian and early Flemish pictures resem
bling the augmenting richness of gems or of stained glass :‡

* Trattato, pp. 103 , 121 , 123 , 324, &c.

Ib. pp. 85, 134.
Absolute opacity, to judge from the older specimens of stained glass,
seems to have been considered inadmissible. The window was to admit light,
however modified and varied, in the form prescribed by the architect, and
that form was to be preserved. This has been unfortunately lost sight of in
some modern glass-painting, which, by excluding the light in large masses,
and adopting the opacity of pictures (the reverse of the influence above al
luded to) , has interfered with the architectural symmetry in a manner far
from desirable. On the other hand, if we suppose painting at any period to
have aimed at the imitation of stained glass, such an imitation must of neces
sity have led to extreme force ; for the painter sets out by substituting a mere
white ground for the real light of the sky, and would thus be compelled to
subdue every tone accordingly. In such an imitation his colour would soon
deepen to its intensest state ; indeed, considerable portions of the darker hues
would be lost in obscurity. The early Flemish pictures seldom err on the side
of a gay superabundance of colour ; on the contrary, they are generally re
366 NOTES .

indeed, it is not impossible that the increase of colour in

shade, which is so remarkable in the pictures alluded to,
may have been originally suggested by the rich and fasci-
nating effect of stained glass ; and the Venetians, in this as
in many other respects, may have improved on a hint bor-
rowed from the early German painters, many of whom
painted on glass. *
At all events, the principle of still increasing in colour in
certain hues seems to have been adopted in Flanders and in
Venice at an early period ; † while Giorgione, in carrying
the style to the most daring extent, still recommended it by
corresponding grandeur of treatment in other respects .
The same general tendency, except that the technical
methods are less transparent, is, however, very striking in
some of the painters of the school of Umbria, the instruc-
tors or early companions of Raphael. The influence of

markable for comparatively cool lights , for extreme depth, and a certain sub-
dued splendour, qualities which would necessarily result from the imitation or
influence in question.
* See Langlois, " Peinture sur Verre." Rouen, 1832 ; Descamps, " La Vie
des Peintres Flamands ;" and Gessert, " Geschichte der Glasmalerei." Stut-
gard, 1839. The antiquity of the glass manufactory of Murano (Venice) is also
not to be forgotten. Vasari objects to the Venetian glass, because it was darker
in colour than that of Flanders, France, and England ; but this very quality
was more likely to have an advantageous influence on the style of the early oil-
painters. The use of stained glass was, however, at no period very general in
Italy.
+ Zanetti, " Della Pittura Veneziana," marks the progress of the early Ve-
netian painters by the gradual use of the warm outline. There are some
mosaics in St. Mark's which have the effect of flesh-colour, but on examina-
tion, the only red colour used is found to be in the outlines and markings.
Many ofthe drawings of the old masters, heightened with red in the shadows,
have the same effect. In these drawings the artists judiciously avoided co-
louring the lips and cheeks much, for this would only have betrayed the want
of general colour, as is observable when statues are so treated.
Andrea di Luigi , called L'Ingegno, and Niccolo di Fuligno, are cited as
the most prominent examples. See Rumohr, " Italienische Forschungen."
Perugino himself occasionally adopted a very glowing colour.
The early Italian schools which adhered most to the Byzantine types appear
to have been also the most remarkable for depth, or rather darkness, of colour.
This fidelity to customary representation was sometimes, as in the schools of
 NOTES . 367

se ofcle these examples, as well as that of Fra Bartolommeo, in

es alinde Florence, is distinctly to be traced in the works of the great
richand artist just named, but neither is so marked as the effect of
lans.E his emulation of a Venetian painter at a later period . The
on a glowing colour, sometimes bordering on exaggeration , which
any of Raphael adopted in Rome, is undoubtedly to be attri-
buted to the rivalry of Sebastian del Piombo. This painter,
in colar the best of Giorgione's imitators, arrived in Rome, invited
ndersal: by Agostini Chigi , in 1511 , and the most powerful of Ra-
in cam phael's frescoes, the Heliodorus and Mass of Bolsena, as
well as some portraits in the same style, were painted in the
mended
two following years. In the hands of some of Raphael's
spects
etechna scholars, again, this extreme warmth was occasionally car-
ried to excess, particularly by Pierino del Vaga, with whom
striking
it often degenerated into redness. The representative of
he instr
fluenced the glowing manner in Florence was Fra Bartolommeo, and,
in the same quality, considered abstractedly, some painters
of the school of Ferrara were second to none.
Licitatio In another Note (par. 177) some further considerations

L
Umbria, and to a certain extent in those of Siena and Bologna, the result of
ice is a religious veneration for the ancient examples ; in others, as in Venice, the
was decis circumstance of frequent intercourse with the Levant is also to be taken into
the account. The Greek pictures of the Madonna, not to mention other repre-
sentations, were extremely dark, in exaggerated conformity, it is supposed,
general'a with the tradition respecting her real complexion (see D'Agincourt, vol . iv.
p. 1) ; a belief which obtained so late as Lomazzo's time, for, speaking of the
Madonna, he observes, " Leggesi però che fu alquanto bruna." Giotto, who
with the independence of genius betrayed a certain contempt for these tradi-
tions, failed perhaps to unite improvement with novelty when he substituted a
pale white flesh-colour for the traditional brown. Some specimens of his
hadows works, still existing at Padua, present a remarkable contrast in this respect
dedor with the earliest productions of the Venetian and Paduan artists. His works
at Florence differ as widely from those of the earlier painters of Tuscany.
This peculiarity was inherited by his imitators, and at one time almost charac-
red# terised the Florentine school. Leon Battista Alberti was not perhaps the
first who objected to it (" Vorrei io che dai pittori fosse comperato il color
bianco assai più caro che le preziosissime gemme." -Della Pittura, l. ii.)
The attachment of Fra Bartolommeo to the grave character of the Christian
olour. types is exemplified in his deep colouring, as well as in other respects.
368 NOTES .

are offered, which may partly explain the prevalence of this

style in the beginning of the sixteenth century ; here we
merely add, that the conditions under which the appearance
itself is most apparent in nature are perhaps more obvious
in Venice than elsewhere.. The colour of general nature
may be observed in all places with almost equal conve-
nience, but with regard to an important quality in living
nature, namely, the colour of flesh, perhaps there are no
circumstances in which its effects at different distances can
be so conveniently compared as when the observer and the
observed gradually approach and glide past each other on
so smooth an element and in so undisturbed a manner as
on the canals and in the gondolas of Venice ; * the com-
plexions, from the peculiar mellow carnations of the Italian
women to the sun-burnt features and limbs of the mariners,
presenting at the same time the fullest variety in another
sense.
At a certain distance the colour being always assumed
to be unimpaired by interposed atmosphere- the reflections
appear kindled to intenser warmth ; the fiery glow of Gior-
gione is strikingly apparent ; the colour is seen in its largest
relation ; the macchia, † an expression so emphatically used
by Italian writers, appears in all its quantity, and the re-
flections being the focus of warmth, the hue seems to
deepen in shade.
A nearer view gives the detail of cooler tints more per-
ceptibly, and the forms are at the same time more distinct.
Hence Lanzi is quite correct when, in distinguishing the
style of Titian from that of Giorgione, he says that Titian's

* Holland might be excepted, and in Holland similar causes may have

had a similar influence.
+ Local colour ; literally, the blot.
Zanetti ventures to single out the picture of Tobit and the Angel in S.
Marziale as the first example of Titian's own manner, and in which a direct
imitation of Giorgione is no longer apparent. In this picture the lights are
cool and the blood-tint very effective.
 NOTES . 369

was at once more defined and less fiery.* In a still nearer

observation the eye detects the minute lights which Leo-
nardo da Vinci says are incompatible with effects such as
those we have described ,† and which, accordingly, we never
find in Giorgione and Titian. This large impression of
colour, which seems to require the condition of comparative
distance for its full effect, was most fitly employed by the
same great artists in works painted in the open air or for
large altar -pieces. Their celebrated frescoes on the exterior
of the Fondaco de' Tedeschi at Venice, to judge from their
faint remains and the descriptions of earlier writers, were
remarkable for extreme warmth in the shadows. The old
frescoes in the open air throughout Friuli have often the
same character, and , owing to the fulness of effect which this
treatment ensures, are conspicuous at a very great distance .‡
In assuming that the Venetian painters may have ac-
quired a taste for this breadth§ of colour under the circum-
stances above alluded to, it is moreover to be remembered
that the time for this agreeable study was the evening ;
when the sun had already set behind the hills of Bassano ;
when the light was glowing but diffused ; when shadows

* " Meno sfumato , men focoso ." -Storia Pittorica.

" La prima cosa che de' colori si perde nelle distanze è il lustro, loro mi-
nima parte."-Trattato, p . 213 ; and elsewhere, " I lumi principali in picciol
luogo son quelli che in picciola distanza sono i primi che si perdono all' occhio."
-p. 128.
A colossal St. Christopher, the usual subject, is frequently seen occupying
the whole height of the external wall of a church. We have here an example
of the influence of religion, such as it was, even on the style of colouring and
practical methods of the art. The mere sight of the image of St. Christopher,
the type of strength, was considered sufficient to reinvigorate those who were
exhausted by the labours of husbandry. The following is a specimen of the
inscriptions inculcating this belief :-
Christophori Sancti speciem quicumque tuetur,
Illo namque die nullo languore tenetur."
Hence the practice of painting the figure on the outside of churches, hence its
colossal size, and hence the powerful qualities in colour above described. See
Maniago, " Storia delle Belle Arti Friulane."
§ The authority of Fuseli sufficiently warrants the application of the term
breadth to colour ; he speaks of Titian's " breadth of local tint."
2 B
370 NOTES.

were soft- conditions all agreeing with the character of

their colouring :* above all, when the hour invited the
fairer portion of the population to betake themselves in
their gondolas to the lagunes. The scene of this " prome
nade" was to the north of Venice, the quarter in which
Titian at one time lived. A letter exists written by Fran
cesco Priscianese, giving an account of his supping with
the great painter in company with Jacopo Nardi , Pietro
Aretino, the sculptor Sansovino, and others. The writer
speaks of the beauty of the garden, where the table was
prepared, looking over the lagunes towards Murano, " which
part of the sea, " he continues, 66 as soon as the sun was
down, was covered with a thousand gondolas, graced with
beautiful women, and enlivened by the harmony of voices
and instruments, which lasted till midnight, forming a
pleasing accompaniment to our cheerful repast."t
To return to Goethe : perhaps the foregoing remarks may
warrant the conclusion that his idea of colour in shadow is
not irreconcileable with the occasional practice of the best
painters. The highest examples of the style thus defined
are, or were, to be found in the works of Giorgione‡ and
Titian, and hence the style itself, though “ within that circle"

* Zanetti quotes an opinion of the painters of his time to the same effect :—
" Teneano essi (alcuni maestri) per cosa certa, che in molte opere Tiziano
volesse fingere il lume-quale si vede nell' inclinarsi del sole verso la sera.
Gli orizzonti assai luminosi dietro le montagne, le ombre incerte e più le car
nagioni brunette e rosseggianti delle figure, gl'induceano a creder questo.”—
Lib. ii. Leonardo da Vinci observes, " Quel corpo che si troverà in mediocre
lume fia in lui poca differenza da' lumi all' ombre . E questo accade sul far
della sera- e queste opere sono dolci ed hacci grazia ogni qualità di volto,"
&c. p. 336. Elsewhere, " Le ombre fatte dal sole od altri lumi particolari
sono senza grazia. "-p. 357 ; see also p . 247.
See " Francesco Priscianese De' Primi Principii della Lingua Latina,"
Venice , 1550. The letter is at the end of the work. It is quoted in Ticozzi's
"Vite de' Pittori Vecelli," Milan, 1817.
The works of Giorgione are extremely rare. The pictures best calculated
to give an idea of the glowing manner for which he is celebrated, are the
somewhat early works and several of the altar-pieces of Titian, the best
specimens of Palma Vecchio, and the portraits of Sebastian del Piombo.
 NOTES . 371

few dare walk," is to be considered the grandest and most

perfect. Its possible defects or abuse are not to be dis
sembled in addition to the danger of exaggeration * it is
seldom united with the plenitude of light and shade, or
with roundness ; yet, where fine examples of both modes of
treatment may be compared, the charm of colour has per
haps the advantage . The difficulty of uniting qualities so
different in their nature, is proved by the very rare instances
in which it has been accomplished . Tintoret in endeavour
ing to add chiaro-scuro to Venetian colour, in almost every
instance fell short of the glowing richness of Titian .‡

* Zanetti and Lodovico Dolce mention Lorenzo Lotto as an instance of the

excess of Giorgione's style. Titian himself sometimes overstepped the mark,
as his biographers confess, and as appears, among other instances, from the
head of St. Peter in the picture (now in the Vatican) in which the celebrated
St. Sebastian is introduced . Raphael was criticised by some cardinals for a
similar defect. See " Castiglione, Il Cortigiano," 1. ii.
In the same paragraph to which the present observations refer, the authority
ofKircher is quoted ; his treatise, " Ars magna lucis et umbra," was published
in Rome in 1646. In a portrait of Nicholas Poussin, engraved by Clouet, the
painter is represented holding a book, which, from the title and the circum
stance of Poussin having lived in Rome in Kircher's time, Goethe supposes to
be the work in question . The abuse of the principle above alluded to, is per
haps exemplified in the red half-tints observable in some of Poussin's figures.
The augmentation of colour in subdued light was still more directly taught
by Lomazzo. He composes the half-tints of flesh merely by diminishing the
quantity of white, the proportions of the other colours employed (for he enters
into minute details) remaining unaltered. See his " Trattato della arte della
Pittura," Milan, 1584, p . 301 .
In the Dresden Gallery, a picture attributed to Titian-at all events a
lucid Venetian picture- hangs next the St. George of Correggio. After
looking at the latter, the Venetian work appears glassy and unsubstantial, but
on reversing the order of comparison, the Correggio may be said to suffer more,
and for a moment its fine transitions of light and shade seem changed to
heaviness.
The finest works of Tintoret -the Crucifixion and the Miracolo del Servo
(considered here merely with reference to their colour, ) may be said to
combine the excellences of Titian and Giacomo Bassan, on a grand scale ; the
sparkling clearness of the latter is one of the prominent characteristics of
these pictures. Tintoret is reported to have once said that a union of his own
knowledge of form with Bassan's colour would be the perfection of painting.
See " Verci Notizie de' Pittori di Bassano ;" Ven. 1775 , p . 61 .
2 B 2
372 NOTES .

Giacomo Bassan and his imitators, even in their dark effects,

still had the principle of the gem in view their light, in
certain hues, is the minimum of colour, their lower tones are
rich, their darks intense, and all is sparkling.* Of the great
painters who, beginning, on the other hand, with chiaro
scuro, sought to combine with it the full richness of colour,
Correggio, in the opinion of many, approached perfection
nearest ; but we may perhaps conclude with greater justice
that the desired excellence was more completely attained by
Rembrandt than by any of the Italians.

NOTE F.- Par. 83.

The author, in these instances, seems to be anticipating

his subsequent explanations on the effect of semi- transparent
mediums. For an explanation of the general view contained
in these paragraphs respecting the gradual increase of co
lour from high light, see the last Note.
The anonymous French work before alluded to , among
other interesting examples, contains a chapter on shadows
cast by the upper light of the sky and coloured by the
setting sun. The effect of this remarkable combination is,
that the light on a wall is most coloured immediately under
a projecting roof, and becomes comparatively neutralised in
proportion to its distance from the edge of the darkest shade .

NOTE G.Par. 98.

" The simplest case of the phenomenon, which Goethe

calls a subjective halo , and one which at once explains its
cause, is the following. Regard a red wafer on a sheet of
white paper, keeping the eye stedfastly fixed on a point at

* That this last quality, the characteristic of Bassan's best pictures, was
held in high estimation by Paul Veronese, is not only evident from that
painter's own works, but from the circumstance of his preferring to place his
sons with Bassan rather than with any other painter. (See “ Boschini Carta del
Navegar," p. 280. ) The Baptism of Sta. Lucilla, in Boschini's time con
sidered the finest of Giacomo's works, is still in the church of S. Valentino, at
Bassano, and may be considered the type of the lucid and sparkling manner.
 NOTES. 373

its center . When the retina is fatigued, withdraw the head

a little from the paper, and a green halo will appear to sur-
round the wafer. By this slight increase of distance the
image of the wafer itself on the retina becomes smaller, and
the ocular spectrum which before coincided with the direct
image, being now relatively larger, is seen as a surrounding
ring." -S. F. Goethe mentions cases of this kind, but does
not class them with subjective halos. See Par. 30 .

NOTE H.- Par. 113 .

66
Cases of this kind are by no means uncommon . Several
interesting ones are related in Sir John Herschell's article on
Light in the Encyclopædia Metropolitana. Careful inves-
tigation has, however, shown that this defect of vision arises
in most, if not in all cases, from an inability to perceive the
red, not the blue rays . The terms are so confounded by the
individuals thus affected, that the comparison of colours in
their presence is the only criterion .” — S. F.

NOTE I.- Par. 135.

The author more than once admits that this chapter on

" Pathological Colours" is very incomplete, and expresses a
wish (Par. 734) that some medical physiologists would in-
vestigate the subject further. This was afterwards in a
great degree accomplished by Dr. Johannes Müller, in his
memoir " Uber die Phantastischen Gesichtserscheinungen. "
Coblentz, 1826. Similar phenomena have been also in-
vestigated with great labour and success by Purkinje . For
a collection of extraordinary facts of the kind recorded by
these writers, the reader may consult Scott's Letters on
Demonology and Witchcraft. * The instances adduced by
Müller and others are, however, intended to prove the in-
herent capacity of the organ of vision to produce light and
colours . In some maladies of the eye, the patient , it seems,

See also a curious passage on the beatific vision of the monks of Mount
Athos, in Gibbon, chap. 63 .
374 NOTES .

suffers the constant presence of light without external light.

The exciting principle in this case is thus proved to be
within , and the conclusion of the physiologists is that ex
ternal light is only one of the causes which produce lumin
ous and coloured impressions. That this view was antici
pated by Newton may be gathered from the concluding
" query" in the third book of his Optics.

NOTE K.-Par. 140.

66 Catoptrical
colours. The colours included under this
head are principally those of fibres and grooved surfaces ;
they can be produced artificially by cutting parallel grooves
on a surface of metal from 2000 to 10,000 in the inch. See
'Brewster's Optics, ' p. 120. The colours called by Goethe
paroptical, correspond with those produced by the diffraction
or inflection of light in the received theory.- See Brewster,
<
p . 95. The phenomena included under the title Epop
tical Colours, ' are generally known as the colours of thin
plates. They vary with the thickness of the film, and the
colour seen by reflection always differs from that seen by
transmission. The laws of these phenomena have been
thoroughly investigated . See Nobili , and Brewster, p . 100. ”
-S . F.
The colours produced by the transmission of polarised
light through chrystalised mediums, were described by
Goethe, in his mode, subsequently to the publication of his
general theory, under the name of Entoptic Colours. See
note to Par. 485 .
NOTE L.- Par. 150 .

We have in this and the next paragraph the outline of

Goethe's system . The examples that follow seem to es
tablish the doctrine here laid down, but there are many
cases which it appears cannot be explained on such prin
ciples : hence, philosophers generally prefer the theory of
absorption, according to which it appears that certain
mediums “ have the property of absorbing some of the com
 NOTES. 375

ponent rays of white light, while they allow the passage of

others. " *
Whether all the facts adduced by Goethe-for instance,
that recorded in Par. 172, are to be explained by this doc
trine, we leave to the investigators of nature to determine.
Dr. Eckermann, in conversing with Goethe, thus described
the two leading phenomena ( 156, 158) as seen by him in the
Alps . " At a distance of eighteen or twenty miles at mid
day in bright sunshine, the snow appeared yellow or even
reddish, while the dark parts of the mountain, free from
snow, were of the most decided blue. The appearances
did not surprise me, for I could have predicted that the
mass of the interposed medium would give a deep yellow
tone to the white snow, but I was pleased to witness the
effect, since it so entirely contradicted the erroneous views of
some philosophers, who assert that the air has a blue-tinging
quality. The observation, said Goethe, is of importance,
and contradicts the error you allude to completely."
The same writer has some observatious to the same effect
on the colour of the Rhone at Geneva. A circumstance of
an amusing nature which he relates in confirmation of
Goethe's theory, deserves to be inserted . " Here (at
Strasburg) , passing by a shop, I saw a little glass bust of
Napoleon, which, relieved as it was against the dark in

* See " Muller's Elements of Physiology," translated from the German by

William Baly, M.D. " The laws of absorption," it has been observed ,
" have not been studied with so much success as those of other phenomena of
physical optics, but some excellent observations on the subject will be found
in Herschell's Treatise on Light in the Encyclopædia Metropolitana , § III.”
" Eckermann's Gespräche mit Goethe," vol. ii . p. 280. Leonardo da Vinci
had made precisely the same observation. " A distant mountain will appear
of a more beautiful blue in proportion as it is dark in colour. The illumined
air, interposed between the eye and the dark mass, being thinner towards the
summit of the mountain, will exhibit the darkness as a deeper blue and vice
versû.”—Trattato della Pittura, p. 143. Elsewhere " The air which in
tervenes between the eye and dark mountains becomes blue ; but it does not
become blue in (before) the light part, and much less in (before) the portion
that is covered with snow ."-p. 244.
376 NOTES .

terior of the room, exhibited every gradation of blue, from

milky light blue to deep violet. I foresaw that the bust
seen from within the shop with the light behind it, would
present every degree of yellow, and I could not resist walk-
ing in and addressing the owner, though perfectly unknown
to me. My first glance was directed to the bust, in which,
to my great joy, I saw at once the most brilliant colours of
the warmer kind, from the palest yellow to dark ruby red.
I eagerly asked if I might be allowed to purchase the bust ;
the owner replied that he had only lately brought it with
him from Paris, from a similar attachment to the emperor
to that which I appeared to feel, but, as my ardour seemed
far to surpass his, I deserved to possess it. So invaluable
did this treasure seem in my eyes, that I could not help
looking at the good man with wonder as he put the bust into
my hands for a few franks. I sent it, together with a curious
medal which I had bought in Milan, as a present to Goethe,
and when at Frankfort received the following letter from
him." The letter, which Dr. Eckermann gives entire, thus
concludes " When you return to Weimar you shall see
the bust in bright sunshine, and while the transparent
countenance exhibits a quiet blue,* the thick mass of the
breast and epaulettes glows with every gradation of warmth,
from the most powerful ruby-red downwards ; and as the
granite statue of Memnon uttered harmonious sounds, so the
dim glass image displays itself in the pomp of colours. The
hero is victorious still in supporting the Farbenlehre. ” †
One effect of Goethe's theory has been to invite the at-
tention of scientific men to facts and appearances which
had before been unnoticed or unexplained . To the above
cases may be added the very common , but very important,
fact in painting, that a light warm colour, passed in a semi-

* This supposes either that the inass was considerably thicker, or that there
was a dark ground behind the head, and a light ground behind the rest of the
figure.
+ " Eckermann's Gespräche mit Goethe," vol . ii . p. 242 .
 NOTES . 377

transparent state over a dark one, produces a cold, bluish

hue, while the operation reversed, produces extreme warmtb.
On the judicious application of both these effects, but espe
cially of the latter, the richness and brilliancy of the best
coloured pictures greatly depends. The principle is to be
recognised in the productions of schools apparently oppo
site in their methods. Thus the practice of leaving the
ground, through which a light colour is apparent, as a
means of ensuring warmth and depth, is very common
among the Dutch and Flemish painters. The Italians,
again, who preferred a solid under-painting, speak of in
ternal light as the most fascinating quality in colour. When
the ground is entirely covered by solid painting, as in the
works of some colourists, the warmest tints in shadows and
reflections have been found necessary to represent it . This
was the practice of Rembrandt frequently, and of Reynolds
universally, but the glow of their general colour is still
owing to its being repeatedly or ultimately enriched on the
above principle. Lastly, the works of those masters who
were accustomed to paint on dark grounds are often heavy
and opaque ; and even where this influence of the ground
was overcome, the effects of time must be constantly dimi
nishing the warmth of their colouring as the surface be
comes rubbed and the dark ground more apparent through
it. The practice of painting on dark grounds was intended
by the Carracci to compel the students of their school to aim
at the direct imitation of the model, and to acquire the use
of the brush ; for the dark ground could only be overcome
by very solid painting. The result answered their expecta
tions as far as dexterity of pencil was concerned, but the
method was fatal to brilliancy of colour. An intelligent
writer of the seventeenth century* relates that Guido adopted
his extremely light style from seeing the rapid change in
some works of the Carracci soon after they were done It

* Scanelli, " Microcosmo della Pittura," Cesena, 1657 , p . 114.

378 NOTES .

is important, however, to remark, that Guido's remedy was

external rather than internal brilliancy ; and it is evident
that so powerless a brightness as white paint can only ac
quire the splendour of light by great contrast, and, above
all, by being seen through external darkness . The secret
of Van Eyck and his contemporaries is always assumed to
consist in the vehicle (varnish or oils) he employed ; but a
far more important condition of the splendour of colour in
the works of those masters was the careful preservation of
internal light by painting thinly, but ultimately with great
force, on white grounds . In some of the early Flemish
pictures in the Royal Gallery at Munich, it may be ob
served, that wherever an alteration was made by the painter,
so that a light colour is painted over a dark one, the colour
is as opaque as in any of the more modern pictures which
are generally contrasted with such works. No quality in
the vehicle could prevent this opacity under such circum
stances ; and on the other hand, provided the internal
splendour is by any means preserved , the vehicle is compara.
tively unimportant.
It matters not (say the authorities on these points) whe
ther the effect in question is attained by painting thinly
over the ground, in the manner of the early Flemish painters
and sometimes of Rubens, or by painting a solid light pre
paration to be afterwards toned to richness in the manner of
the Venetians. Among the mechanical causes of the clear
ness of colours superposed on a light preparation may be
mentioned that of careful grinding. All writers on art who
have descended to practical details have insisted on this.
From the appearance of some Venetian pictures it may be
conjectured that the colours of the solid under- painting
were sometimes less perfectly ground than the scumbling
colours (the light having to pass through the one and to be
reflected from the other) . The Flemish painters appear to
have used carefully-ground pigments universally. This is
very evident in Flemish copies from Raphael, which, though
 NOTES. 379

equally impasted with the originals , are to be detected , among

other indications, by the finely-ground colours employed.

NOTE M.- Par. 177.

Without entering further into the scientific merits or de-

merits of this chapter on the " First Class of Dioptrical
Colours," it is to be observed that several of the examples
correspond with the observations of Leonardo da Vinci,
and again with those of a much older authority, namely,
Aristotle. Goethe himself admits, and it has been remarked
by others, that his theory, in many respects, closely resem-
bles that of Aristotle : indeed he confesses * that at one
time he had an intention of merely paraphrasing that philo-
sopher's Treatise on Colours .†
We have already remarked (Note on par. 150) that
Goethe's notion with regard to the production of warm
colours, by the interposition of dark transparent mediums
before a light ground, agrees with the practice of the best
schools in colouring ; and it is not impossible that the same
reasons which may make this part of the doctrine generally
acceptable to artists now, may have recommended the very
similar theory of Aristotle to the painters of the fifteenth
and sixteenth centuries : at all events, it appears that the
ancient theory was known to those painters,
It is unnecessary to dwell on the fact that the doctrines
of Aristotle were enthusiastically embraced and generally
inculcated at the period in question ; but it has not been

"Geschichte der Farbenlehre," in the " Nachgelassene Werke." Cotta,

1833.
The treatise in question is ascribed by Goethe to Theophrastus, but it is
included in most editions of Aristotle, and even attributed to him in those
which contain the works of both philosophers ; for instance, in the Aldine
Princeps edition, 1496. Calcagnini says, the treatise is made up of two sepa-
rate works on the subject, both by Aristotle.
His authority seems to have been equally great on subjects connected
with the phenomena of vision : the Italian translator of a Latin treatise, by
Portius, on the structure and colours of the eye, thus opens his dedication to
the Cardinal Ercole Gonzaga, of Mantua :-" Grande anzi quasi infinito è
380 NOTES .

observed that the Italian writers who translated, para-

phrased, and commented on Aristotle's Treatise on Colours
in particular, were in several instances the personal friends
of distinguished painters. Celio Calcagnini* had the highest
admiration for Raphael ; Lodovico Dolcef was the eulogist
of Titian ; Portius, whose amicable relations with the Flo-
rentine painters may be inferred from various circumstances,
lectured at Florence on the Aristotelian doctrines early in
the sixteenth century. The Italian translations were later,
but still prove that these studies were undertaken with re-
ference to the arts, for one of them is dedicated to the
painter Cigoli .§

l'obligo che ha il mondo con quel più divino che umano spirito di Aristo-
tile."
In a letter to Ziegler the mathematician, Calcagnini speaks of Raphael
as "the first of painters in the theory as well as in the practice of his art."
This expression may, however, have had reference to a remarkable circum-
stance mentioned in the same letter, namely, that Raphael entertained the
learned Fabius of Ravenna as a constant guest, and employed him to translate
Vitruvius into Italian. This MS. translation, with marginal notes, written
by Raphael, is now in the library at Munich. "'Passavant, Rafael von Urbino."
+ Lodovico Dolce's Treatise on Colours ( 1565) is in the form of a dialogue,
like his " Aretino ." The abridged theory of Aristotle is followed by a trans-
lation of the Treatise of Antonius Thylesius on Colours ; this is adapted to the
same colloquial form, and the author is not acknowledged : the book ends
with an absurd catalogue of emblems. The " Somma della Filosofia d'Aris-
totile," published earlier by the same author, is a very careless performance.
A Latin translation of Aristotle's Treatise on Colours, with comments by
Simon Portius, was first published , according to Goethe, at Naples in 1537.
In a later Florentine edition, 1548, dedicated to Cosmo I., Portius alludes to
his having lectured at an earlier period in Florence on the doctrines of Aris-
totle, at which time he translated the treatise in question. Another Latin
translation, with notes, was published later in the same century at Padua—
" Emanuele Marguino Interprete :" but byfar the clearest view of the Aristo-
telian theory is to be found in the treatise of Antonio Vidi Scarmiglione of
Fuligno (" De Coloribus," Marpurgi, 1591 ) . It is dedicated to the Emperor
Rudolph II. Of all the paraphrases of the ancient doctrine this comes nearest
to the system of Goethe ; but neither this nor any other of the works alluded
to throughout this Note are mentioned by the author in his History of the
Doctrine of Colours, except that of Portius.
An earlier Italian translation appeared in Rome, 1535. See " Argelatus
Biblioteca degli Volgarizzatori."
 NOTES. 381

The writers on art, from Leon Battista Alberti to Bor-

ghini, without mentioning later authorities, either tacitly
coincide with the Aristotelian doctrine, or openly profess
to explain it. It is true this is not always done in the
clearest manner, and some of these writers might say with
Lodovico Dolce , " I speak of colours, not as a painter, for
that would be the province of the divine Titian ."
Leonardo da Vinci in his writings, as in everything else,
appears as an original genius. He now and then alludes
generally to opinions of " philosophers," but he quotes no
authority ancient or modern. Nevertheless, a passage on
the nature of colours, particularly where he speaks of the
colours of the elements, appears to be copied from Leon
Battista Alberti,* and from the mode in which some of
Leonardo's propositions are stated, it has been supposed †
that he had been accustomed at Florence to the form of the
Aristotelian philosophy. At all events, some of the most
important of his observations respecting light and colours,
have a great analogy with those contained in the treatise in
question. The following examples will be sufficient to
prove this coincidence ; the corresponding passages in
Goethe are indicated, as usual, by the numbers of the para-
graphs ; the references to Leonardo's treatise are given at
the bottom of the page.

ARISTOTLE .

" A vivid and brilliant red appears when the weak rays of
the sun are tempered by subdued and shadowy white."-
154.
LEONARDO .
" The air which is between the sun and the earth at sun-

"Della Pittura e della Statua," Lib. 1 , p. 16 , Milan edition, 1804. Com-

pare with the " Trattato della Pittura," p. 141. Other points of resemblance
are to be met with. The notion of certain colours appropriated to the four
elements, occurs in Aristotle, and is indeed attributed to older writers.
See the notes to the Roman edition of the " Trattato della Pittura."
382 NOTES.

rise or sun- set, always invests what is beyond it more than

any other (higher) portion of the air : this is because it is
whiter."""*

A bright object loses its whiteness in proportion to its

distance from the eye much more when it is illuminated by
the sun, for it partakes of the colour of the sun mingled with
the colour (tempered by the mass ) of the air interposed be
tween the eye and the brightness . †

ARISTOTLE .

" If light is overspread with much obscurity, a red colour

appears ; if the light is brilliant and vivid, this red changes
to a flame- colour. " - 150 , 160 .

LEONARDO .
66
This (the effect of transparent colours on various
grounds) is evident in smoke, which is blue when seen
against black, but when it is opposed to the (light) blue
sky, it appears brownish and reddening. " §

ARISTOTLE.

"White surfaces as a ground for colours, have the effect

of making the pigments appear in greater splendour.”
594, 902.

* Page
237.
+ Page 301
In the Treatise De Igne, by Theophrastus, we find the same notion thus
pressed : " Brightness (rò vxov) seen through a dark coloured medium
(dià TỸ μídavos) appears red ; as the sun seen through smoke or soot : hence
the coal is redder than the flame." Scarmiglione, from whom Kircher seems
to have copied, observes :-" Itaque color realis est lux opaca ; licet id e
plurimis apparentiis colligere. Luna enim in magnâ solis eclipsi rubra con
spicitur, quia tenebris lux præpeditur ac veluti tegitur. " -De Coloribus.
§ Page 122.
Tà även : translated flores by Calcagnini and the rest, by Goethe, die
Blüthe, the bloom. That the word sometimes signified pigments is sufficiently
apparent from the following passage of Suidas (quoted by Emeric David, " Dis
cours Historiques sur la Peinture Moderne'' ) ἄνθεσι κεκοσμημέναι, οιον ψιμμύθιον
 NOTES . 383

LEONARDO.

" To exhibit colours in their beauty, the whitest ground

should be prepared. I speak of colours that are (more or
less) transparent ."*
ARISTOTLE .
66
The air near us appears colourless ; but when seen in
depth, owing to its thinness it appears blue ; † for where the
light is deficient (beyond it) , the air is affected by the dark
ness and appears blue : in a very accumulated state, how
ever, it appears, as is the case with water, quite white .”
155, 158.
LEONARDO .

" The blue of the atmosphere is owing to the mass of

illuminated air interposed between the darkness above and
the earth . The air in itself has no colour, but assumes
qualities according to the nature of the objects which are
beyond it . The blue of the atmosphere will be the more
intense in proportion to the degree of darkness beyond it :"
elsewhere " if the air had not darkness beyond it, it would
be white. "‡
ARISTOTLE.

" We see no colour in its pure state, but every hue is

variously intermingled with others : even when it is unin
fluenced by other colours, the effect of light and shade
modifies it in various ways, so that it undergoes alterations
and appears unlike itself. Thus, bodies seen in shade or in

Qúncı xai rois ópolis . Variis pigmentis ornatæ, ut cerussâ, fuco, et aliis similibus.
(Suid. in voc. ' Eğnvdroμiva..) A panel prepared for painting, with a white
ground consolidated with wax, and perhaps mastic, was found in Herculaneum.
* Page 114.
† Ἐν βάθει δὲ θεωρουμένου ἐγγυτάτω φαίνεται τῷ χρώματι κυανοειδὴς διὰ τὴν
ἀραιότητα. " But when seen in depth, it appears (even) in its nearest colour,
blue, owing to its thinness." The Latin interpretations vary very much
throughout. The point which is chiefly important is however plain enough,
viz. that darkness seen through-a light medium is blue.
Page 136-430 .
384 NOTES.

light, in more pronounced or softer sun-shine, with their

surfaces inclined this way or that, with every change exhibit
a different colour."
LEONARDO.
"No substance will ever exhibit its own hue unless the
light which illumines it is entirely similar in colour. It very
rarely happens that the shadows of opaque bodies are really
similar (in colour ) to the illumined parts. The surface
of every substance partakes of as many hues as are reflected
from surrounding objects ."*
ARISTOTLE .

" So , again, with regard to the light of fire, of the moon,

or of lamps, each has a different colour, which is variously
combined with differently coloured objects."

LEONARDO .

" We can scarcely ever say that the surface of illumined

bodies exhibits the real colour of those bodies. Take a

white band and place it in the dark, and let it receive light
by means of three apertures from the sun, from fire, and
from the sky the white band will be tricoloured ." †

ARISTOTLE .
66
When the light falls on any object and assumes (for
example) a red or green tint, it is again reflected on other
substances, thus undergoing a new change But this effect,
though it really takes place, is not appreciable by the eye :
though the light thus reflected to the eye is composed of a
variety of colours, the principal of these only are dis-
tinguishable . "
LEONARDO.

"No colour reflected on the surface of another colour,

tinges that surface with its own colour (merely), but will be

* Page 121 , 306 , 326 , 387. + Page 366.

 NOTES . 385

mixed with various other reflections impinging on the same

surface " but such effects, he observes elsewhere, " are
""**
scarcely, if at all, distinguishable in a very diffused light . "

ARISTOTLE .
66
Thus, all combinations of colours are owing to three
causes ; the light, the medium through which the light
appears, such as water or air, and lastly the local colour
from which the light happens to be reflected ."

LEONARDO.
66
All illumined objects partake of the colour of the light
they receive .
" Every opaque surface partakes of the colour of the
intervening transparent medium, according to the density of
such medium and the distance between the eye and the
object.
" The medium is of two kinds ; either it has a surface,
like water, & c. , or it is without a common surface, like the
air."t
In the observations on trees and plants more points of
resemblance might be quoted ; the passages corresponding
with Goethe's views are much more numerous.
It is remarkable that Leonardo, in opposition, it seems to
some authorities, agrees with Aristotle in reckoning black
and white as colours, placing them at the beginning and end
of the scale.§ Like Aristotle, again, he frequently makes
use of the term black, for obscurity ; he even goes further,

* Page 104, 369.

† Page 236, 260, 328.
‡ " De' semplici colori il primo è il bianco : benchè i filosofi non accettano
nè il bianco nè il nero nel numero de' colori ." -p. 125 , 141 . Elsewhere,
however, he sometimes adopts the received opinion.
§ Leon Battista Alberti, in like manner observes :-" Affermano (i filosofi)
che le spezie de' colori sono sette, cioè, che il bianco ed il nero sono i duoi
estremi, infra i quali ve n'è uno nel mezzo (rosso) e che infra ciascuno di
questi duoi estremi e quel del mezzo, da ogni parte ve ne sono due altri." An
absurd statement of Lomazzo, p. 190 , is copied verbatim from Lodovico Dolce
2 c
386 NOTES .

for he seems to consider that blue may be produced by the

actual mixture of black and white, provided they are pure.
The ancient author, however, explains himself on this point
as follows- " We must not attempt to make our observa
tions on these effects by mixing colours as painters mix them ,
but by remarking the appearances as produced by the rays
of light mingling with each other."+
When we consider that Leonardo's Treatise professes to
embrace the subject of imitation in painting, and that Aris
totle's briefly examines the physical nature and appearance
of colours, it must be admitted that the latter sustains the
above comparison with advantage ; and it is somewhat ex
traordinary that observations indicating so refined a know
ledge of nature, as regards the picturesque, should not have
been taken into the account, for such appears to be the
fact, in the various opinions and conjectures that have been
expressed from time to time on the painting of the Greeks.
The treatise in question must have been written when
Apelles painted, or immediately before ; and as a proof

( Somma della Filos . d'Arist.) ; but elsewhere , p. 306 , Lomazzo agrees with
Alberti . Aristotle seems to have misled the two first, for after saying there
are seven colours, he appears only to mention six : he says " There are seven
colours, if brown is to be considered equivalent to black, which seems reason
able. Yellow, again, may be said to be a modification of white. Between
these we find red, purple, green, and blue."-De Sensu et Sensili. Perhaps
it is in accordance with this passage that Leonardo da Vinci reckons eight
colours.-Trattato, p. 126 .
* Page 122, 142 , 237.
On the authority of this explanation the word μíλav has sometimes been
translated in the foregoing extracts obscurity, darkness.
Raffaello Borghini, in his attempt to describe the doctrine of Aristotle with
a view to painting, observes " There are two principles which concur in the
production of colour, namely, light and transparence." But he soon loses this
clue to the best part of the ancient theory, and when he has to speak of the
derivation of colours from white and black, he evidently understands it in a
mere atomic sense, and adds-" I shall not at present pursue the opinion of
Aristotle, who assumes black and white as principal colours, and considers all
the rest as intermediate between them."-Il Riposo, 1. ii. Accordingly, like
Lodovico Dolce, he proceeds to a subject where he was more at home, namely,
the symbolical meaning of colours.
 NOTES . 387

that Aristotle's remarks on the effect of semi-transparent

mediums were not lost on the artists of his time, the follow
ing passage from Pliny is subjoined, for, though it is well
known, it acquires additional interest from the foregoing
extracts.
" He (Apelles) passed a dark colour over his pictures
when finished, so thin that it increased the splendour of the
tints, while it protected the surface from dust and dirt : it
could only be seen on looking into the picture. The effect
of this operation, judiciously managed, was to prevent the
colours from being too glaring, and to give the spectator the
impression of looking through a transparent crystal. At
the same time it seemed almost imperceptibly to add a
certain dignity of tone to colours that were too florid."
" This," says Reynolds, " is a true and artist -like descrip
tion of glazing or scumbling, such as was practised by
Titian and the rest of the Venetian painters."
The account of Pliny has, in this instance, internal evi
dence of truth, but it is fully confirmed by the following
passage in Aristotle :-" Another mode in which the effect
of colours is exhibited is when they appear through each
other, as painters employ them when they glaze (¿ñaλɛi
POVTes)* a (dark) colour over a lighter one ; just as the sun,
which is in itself white, assumes a red colour when seen
through darkness and smoke. This operation also ensures
a variety of colours, for there will be a certain ratio between
those which are on the surface and those which are in
depth." -De Sensu et Sensili.
Aristotle's notion respecting the derivation of colours
from white and black may perhaps be illustrated by the
following opinion on the very similar theory of Goethe.
" Goethe and Seebeck regard colour as resulting from
the mixture of white and black, and ascribe to the different

* This word is only strictly applied to unctuous substances, and may confirm
the views of those writers who have conjectured that asphaltum was a chief
ingredient in the atramentum of the ancients.
2 c2
 388 NOTES .

colours a quality of darkness (oxisgov ) , by the different de

grees of which they are distinguished, passing from white to
black through the gradations of yellow, orange, red , violet,
and blue, while green appears to be intermediate again be-
tween yellow and blue . This remark, though it has no
influence in weakening the theory of colours proposed by
Newton, is certainly correct, having been confirmed experi-
mentally by the researches of Herschell, who ascertained
the relative intensity of the different coloured rays by illu-
minating objects under the microscope by their means, &c.
" Another certain proof of the difference in brightness of
the different coloured rays is afforded by the phenomena of
ocular spectra. If, after gazing at the sun, the eyes are
closed so as to exclude the light, the image of the sun ap-
pears at first as a luminous or white spectrum upon a dark
ground, but it gradually passes through the series of colours
to black, that is to say, until it can no longer be distin-
guished from the dark field of vision ; and the colours
which it assumes are successively those intermediate be-
tween white and black in the order of their illuminating
power or brightness, namely, yellow, orange, red , violet,
and blue. If, on the other hand, after looking for some
time at the sun we turn our eyes towards a white surface,
the image of the sun is seen at first as a black spectrum
upon the white surface, and gradually passes through the
different colours from the darkest to the lightest, and at
last becomes white, so that it can no longer be distinguished
from the white surface "*-See par. 40, 44 .
It is not impossible that Aristotle's enumeration of the
colours may have been derived from, or confirmed by, this
very experiment. Speaking of the after-image of colours
he says, " The impression not only exists in the sensorium
in the act of perceiving, but remains when the organ is at
rest. Thus if we look long and intently on any object,

" Elements of Physiology," by J. Muller, M.D., translated from the Ger-

man by William Baly, M.D. London, 1839.
 NOTES . 389

when we change the direction of the eyes a responding

colour follows . If we look at the sun, or any other very
bright object, and afterwards shut our eyes, we shall, as if
in ordinary vision, first see a colour of the same kind ; this
will presently be changed to a red colour, then to purple,
and so on till it ends in black and disappears."— De Insom-
niis.

NOTE N.Par. 246.

66
The appearance of white in the centre, according to
the Newtonian theory, arises from each line of rays forming
its own spectrum. These spectra, superposing each other
on all the middle part, leave uncorrected (unneutralised)
colours only at the two edges. " - S. F. *

NOTE O.-- Par. 252.

These experiments with grey objects, which exhibit dif-

ferent colours as they are on dark or light grounds, were
suggested, Goethe tells us, by an observation of Antonius
Lucas, of Lüttich, one of Newton's opponents, and, in the
opinion of the author, one of the few who made any well-
founded objections. Lucas remarks, that the sun acts
merely as a circumscribed image in the prismatic experi-
ments, and that if the same sun had a lighter background
than itself, the colours of the prism would be reversed .
Thus in Goethe's experimenis, when the grey disk is on a
dark ground, it is edged with blue on being magnified ;
when on a light ground it is edged with yellow. Goethe
acknowledges that Lucas had in some measure anticipated
his own theory.- Vol . ii. p. 440.

NOTE P.- Par. 284.

The earnestness and pertinacity with which Goethe in-

* This was objected to Goethe when his " Beyträge zur Optik" first ap-
peared ; he answered the objection by a coloured diagram in the plates to the
"Farbenlehre :" in this he undertakes to show that the assumed gradual
"correction" of the colours would produce results different from the actual
appearance in nature.
390 NOTES .

sisted that the different colours are not subject to different

degrees of refrangibility are at least calculated to prove that
he was himself convinced on the subject, and, however ex-
traordinary it may seem, his conviction appears to have been
the result of infinite experiments and the fullest ocular evi-
dence . He returns to the question in the controversial
division of his work, in the historical part, and again in the
description of the plates. In the first he endeavours to
show that Newton's experiment with the blue and red paper
depends entirely on the colours being so contrived as to
appear elongated or curtailed by the prismatic borders.
" If," he says, " we take a light- blue instead of a dark one,
the illusion (in the latter case) is at once evident. Accord-
ing to the Newtonian theory the yellow-red (red) is the
least refrangible colour, the violet the most refrangible .
Why, then, does Newton place a blue paper instead of a
violet next the red ? If the fact were as he states it, the
difference in the refrangibility of the yellow-red and violet
would be greater than in the case of the yellow- red and
blue. But here comes in the circumstance that a violet
paper conceals the prismatic borders less than a dark- blue
paper, as every observer may now easily convince himself,"
& c. -Polemischer Theil, par. 45. Desaguliers, in repeat-
ing the experiment, confessed that if the ground of the
colours was not black, the effect did not take place so well.
Goethe adds, " not only not so well, but not at all . "- His-
torischer Theil, p. 459. Lucas of Lüttich, one of Newton's
first opponents, denied that two differently- coloured silks are
different in distinctness when seen in the microscope.
Another experiment proposed by him, to show the un-
soundness of the doctrine of various refrangibility, was the
following :-Let a tin plate painted with the prismatic co-
lours in stripes be placed in an empty cubical vessel, so
that from the spectator's point of view the colours may be
just hidden by the rim . On pouring water into this vessel ,
all the colours become visible in the same degree ; whereas,
it was contended , if the Newtonian doctrine were true, some
 NOTES . 391

colours would be apparent before others.- Historischer

Theil, p. 434.
Such are the arguments and experiments adduced by
Goethe on this subject ; they have all probably been an
swered. In his analysis of Newton's celebrated Experi
mentum Crucis, he shows again that by reversing the pris
matic colours (refracting a dark instead of a light object) ,
the colours that are the most refrangible in Newton's expe
riment become the least so, and vice versá.
Without reference to this objection, it is now admitted
that " the difference of colour is not a test of difference of
refrangibility, and the conclusion deduced by Newton is no
longer admissible as a general truth, that to the same de
gree of refrangibility ever belongs the same colour, and to
the same colour ever belongs the same degree of refrangi
bility. " -Brewster's Optics, p. 72.

NOTE Q.- Par . 387.

With the exception of two very inconclusive letters to

Sulpice Boisserée, and some incidental observations in the
conclusion of the historical portion under the head of en
toptic colours, Goethe never returned to the rainbow.
Among the plates he gave the diagram of Antonius de Do
minis. An interesting chapter on halos, parhelia, and
paraselena, will be found in Brewster's Optics, p . 270.

NOTE R.- Par. 478.

The most complete exhibition of the colouring or mant

ling of metals was attained by the late Cav. Nobili, pro
fessor of physical science in Florence. The general mode
in which these colours are produced is thus explained by
him :*
66
A point of platinum is placed vertically at the distance
of about half a line above a lamina of the same metal laid

* See " Memorie ed Osservazioni, edite et inedite del Cav. Professor No

bili," Firenze, 1834.
392 NOTES .

horizontally at the bottom of a vessel of glass or porcelain.

Into this vessel a solution of acetate of lead is poured so as
to cover not only the lamina of platinum, but two or three
lines of the point as well . Lastly, the point is put in com
munication with the negative pole of a battery, and the
lamina with the positive pole. At the moment in which
the circuit is completed a series of coloured rings is pro
duced on the lamina under the point similar to those ob
served by Newton in lenses pressed together."
The scale of colours thus produced corresponds very
nearly with that observed by Newton and others in thin
plates and films, but it is fuller, for it extends to forty-four
tints. The following list, as given by Nobili , is divided
by him into four series to agree with those of Newton : the
numbers in brackets are those of Newton's scale . The
Italian terms are untranslated , because the colours in some
cases present very delicate transitions . *

First Series.
1. Biondo argentino (4) . † 6. Fulvo acceso.
2. Biondo . 7. Rosso di rame (6) .
3. Biondo d'oro. 8. Ocria.
4. Biondo acceso (5) . 9. Ocria violacea.
5. Fulvo . 10. Rosso violaceo (7).

Second Series.
11. Violetto (8 ) . 20. Giallo acceso.
12. Indaco ( 10). 21. Giallo - rancio.
13. Blu carico . 22. Rancio ( 13) .
14. Blu . 23. Rancio-rossiccio.
15. Blu chiaro ( 11 ) . 24. Rancio-rosso.
16. Celeste. 25. Rosso-rancio.
17. Celeste-giallognolo. 26. Lacca-rancia ( 14 ) .
18. Giallo chiarissimo ( 12) . 27. Lacca.
19. Giallo. 28. Lacca accesa ( 15) .

* The colours in some of the compound terms are in a manner mutually

neutralising ; such terms might, no doubt, be amended.
† The three first numbers in Newton's scale are black, blue, and white.
 NOTES . 393

Third Series.

29. Lacca-purpurea ( 16). 34. Verde-giallo (20) .

30. Lacca-turchiniccia (17). 35. Verde-rancio.
31. Porpora- verdognola ( 18) . 36. Rancio-verde (21 ) .
32. Verde ( 19) . 37. Rancio-roseo.
33. Verde giallognolo. 38. Lacca-rosea (22).

Fourth Series.

39. Lacca-violacea (24). 43. Verde-giallo rossiccio

40. Violaceo-verdognolo (25 ). (28) .
41. Verde (26) . 44. Lacca-rosea (30) .
42. Verde-giallo (27) .

"These tints, " Professor Nobili observes, " are disposed

according to the order of the thin mantlings which occasion
them ; the colour of the thinnest film is numbered 1 ; then
follow in order those produced by a gradual thickening of
the medium. I cannot deceive myself in this arrangement,
for the thin films which produce the colours are all applied
with the same electro-chemical process. The battery, the
solution, the distances, &c., are always the same ; the only
difference is the time the effect is suffered to last. This
is a mere instant for the colour of No. 1 , a little longer for
No. 2, and so on, increasing for the succeeding numbers .
Other criterions, however, are not wanting to ascertain the
place to which each tint belongs. "
The scale differs from that of Newton, inasmuch as there
is no blue in Nobili's first series and no green in the se-
cond : green only appears in the third and fourth series.
" The first series, " says the Professor, " is remarkable for
the fire and metallic appearance of its tints, the second for
clearness and brilliancy, the third and fourth for force and
richness." The fourth, he observes, has the qualities of
the third in a somewhat lesser degree, but the two greens
are very nearly alike.
It is to be observed, that red and green are the principal
394 NOTES .

ingredients in the third and fourth series, blue and yellow

in the second and first.

NOTE S. - Par. 485 .

A chapter on entoptic colours, contained in the supple-

ment to Goethe's works, was translated with the intention
of inserting it among the notes, but on the whole it was
thought most advisable to omit it. Like many other parts
of the " Doctrine of Colours " it might have served as a
specimen of what may be achieved by accurate observation
unassisted by a mathematical foundation. The whole
theory of the polarization of light has, however, been so
fully investigated since Goethe's time, that the chapter in
question would probably have been found to contain very
little to interest scientific readers, for whom it seems chiefly
to have been intended . One observation occurs in it which
indeed has more reference to the arts ; in order to make
this intelligible, the leading experiment must be first de-
scribed, and for this purpose the following extracts may
serve .

3. *

" The experiment, in its simplest form, is to be made as

follows :-let a tolerably thick piece of plate-glass be cut
into several squares of an inch and a half ; let these be
heated to a red heat and then suddenly cooled . The
squares of glass which do not split in this operation are now
fit to produce the entoptic colours.

4.

" In our mode of exhibiting the phenomenon, the ob-

server is, above all, to betake himself, with his apparatus
to the open air. All dark rooms , all small apertures (fora-

* The numbers, as usual, indicate the corresponding paragraphs in the

original.
 "
1

NOTES. 395

mina exigua) , * are again to be given up. A pure, cloud

less sky is the source whence we are to derive a satisfactory
insight into these appearances.

5.

" The atmosphere being clear, let the observer lay the
squares above described on a black surface, so placing them
that two sides may be parallel with the plane of vision.
When the sun is low, let him hold the squares so as to re
flect to the eye that portion of the sky opposite to the sun,
and he will then perceive four dark points in the four cor
ners of a light space . If, after this, he turn towards the
quarters of the sky at right angles with that where his first
observation was made, he will see four bright points on a
dark ground : between the two regions the figures appear
to fluctuate.

6.

"From this simple reflection we now proceed to another,

which, but little more complicated, exhibits the appearance
much more distinctly. A solid cube of glass, or in its stead
a cube composed of several plates, is placed on a black
mirror, or held a little inclined above it , at sun-rise or sun
set. The reflection of the sky being now suffered to fall
through the cube on the mirror, the appearance above de
scribed will appear more distinctly. The reflection of the
sky opposite to the sun presents four dark points on a light W
ground ; the two lateral portions of the sky present the
contrary appearance, namely, four light points on a dark
ground. The space not occupied by the corner points ap
pears in the first case as a white cross, in the other as a
1
black cross, expressions hereafter employed in describing
the phenomena. Before sun-rise or after sun- set, in a very

* In the historical part, Goethe has to speak of so many followers of New

ton who begin their statements with " Si per foramen exiguum," that the
term is a sort of by-word with him.
 396 NOTES.

subdued light, the white cross appears on the side of the

sun also. *
"We thus conclude that the direct reflection of the sun
produces a light figure, which we call a white cross ; the
oblique reflection gives a dark figure, which we call a black
cross . If we make the experiment all round the sky, we
shall find that a fluctuation takes place in the intermediate
regions."
We pass over a variety of observations on the modes of
exhibiting this phenomenon, the natural transparent sub-
stances which exhibit it best, and the detail of the colours
seen within them, and proceed to an instance where the
author was enabled to distinguish the " direct" from the
"oblique" reflection by means of the entoptic apparatus,
in a painter's study.

40.
66
' An excellent artist, unfortunately too soon taken from
us, Ferdinand Jagemann, who, with other qualifications, had
a fine eye for light and shade, colour and keeping, had built
himself a painting-room for large as well as small works .
The single high window was to the north, facing the most
open sky, and it was thought that all necessary requisites
had been sufficiently attended to .
" But after our friend had worked for some time, it ap-
peared to him, in painting portraits, that the faces he copied
were not equally well lighted at all hours of the day, and
yet his sitters always occupied the same place, and the se-
renity of the atmosphere was unaltered .
“ The variations of the favourable and unfavourable light
had their periods during the day. Early in the morning
the light appeared most unpleasantly grey and unsatisfac-

At mid-day on the 24th of June the author observed the white cross re-
flected from every part of the horizon. At a certain distance from the sun,
corresponding, he supposes, with the extent of halos, the black cross appeared.
Whence the term entoptic.
 NOTES . 397

¿. tory ; it became better, till at last, about an hour before

noon, the objects had acquired a totally different appear
is ance. Everything presented itself to the eye of the artist
སྨིཾ in its greatest perfection, as he would most wish to transfer
[12 it to canvas. In the afternoon this beautiful appearance
vanished-the light became worse, even in the brightest
day, without any change having taken place in the atmo
sphere.
66
DAS 'As soon as I heard of this circumstance, I at once con

Fax nected it in my own mind with the phenomena which I had

been so long observing, and hastened to prove, by a phy
sical experiment, what a clear-sighted artist had discovered
Exa entirely of himself, to his own surprise and astonishment.
66
" I had the second* entoptic apparatus brought to the
spot, and the effect on this was what might be conjectured
from the above statement. At mid-day, when the artist
saw his model best lighted, the north, direct reflection gave
the white cross ; in the morning and evening, on the other
*7
hand, when the unfavourable oblique light was so unplea
0
sant to him, the cube showed the black cross ; in the inter
mediate hours the state of transition was apparent. "
The author proceeds to recal to his memory instances
De where works of art had struck him by the beauty of their
appearance owing to the light coming from the quarter op
posite the sun, in " direct reflection , " and adds, " Since these
decided effects are thus traceable to their cause, the friends
2192 of art, in looking at and exhibiting pictures, may enhance
#
the enjoyment to themselves and others by attending to a
132B fortunate reflection."

lehe Before described : the author describes several others more or less com
plicated, and suggests a portable one. "Such plates, which need only be an
inch and a quarter square, placed on each other to form a cube, might be set
in a brass case, open above and below. At one end of this case a black mir
ror with a hinge, acting like a cover, might be fastened . We recommend
this simple apparatus, with which the principal and original experiment may
be readily made. With this we could, in the longest days, better define the
THEW circle round the sun where the black cross appears," &c.
398 NOTES.

NOTE T.- Par. 496.

"Since Goethe wrote, all the earths have been decom

posed, and have been shown to be metallic bases united
with oxygen ; but this does not invalidate his statement . ”
S. F.

NOTE U.- Par. 502.

The cold nature of black and its affinity to blue are

assumed by the author throughout ; if the quality is opaque,
and consequently greyish, such an affinity is obvious , but
in many fine pictures, intense black seems to be considered
as the last effect of heat, and in accompanying crimson and
orange may be said rather to present a difference of degree
than a difference of kind. In looking at the great picture
of the globe, we find this last result produced in climates
where the sun has greatest power, as we find it the imme
diate effect of fire. The light parts of black animals are
often of a mellow colour ; the spots and stripes on skins
and shells are generally surrounded by a warm hue, and
are brown before they are absolutely black. In combus
tion, the blackness which announces the complete ignition,
is preceded always by the same mellow, orange colour .
The representation of this process was probably intended
by the Greeks in the black and subdued orange of their
vases : indeed, the very colours may have been first pro
duced in the kiln. But without supposing that they were
retained merely from this accident, the fact that the combi
nation itself is extremely harmonious, would be sufficient
to account for its adoption . Many of the remarks of
Aristotle* and Theophrastus† on the production of black,
are derived from the observation of the action of fire, and
on one occasion, the former distinctly alludes to the terra
cotta kiln. That the above opinion as to the nature of
black was prevalent in the sixteenth century, may be in

* De Coloribus." + " De Igne."

 NOTES. 399

ferred from Lomazzo, who observes,-" Quanto all' origine

e generazione de' colori, la frigidità è la madre della bian-
""*
chezza : il calore è padre del nero .' The positive cold-
ness of black may be said to begin when it approaches
grey. When Leonardo da Vinci says that black is most
beautiful in shade, he probably means to define its most
intense and transparent state, when it is furthest removed
from grey .

NOTE V.- Par. 555.

The nature of vehicles or liquid mediums to combine

with the substance of colours, has been frequently discussed
by modern writers on art, and may perhaps be said to have
received as much attention as it deserves. Reynolds smiles
at the notion of our not having materials equal to those of
former times, and indeed, although the methods of indivi-
duals will always differ, there seems no reason to suppose
that any great technical secret has been lost. In these in-
quiries, however, which relate merely to the mechanical
causes of bright and durable colouring, the skill of the
painter in the adequate employment of the higher resources
of his art is, as if by common consent, left out of the account,
and without departing from this mode of considering the
question, we would merely repeat a conviction before ex-
pressed, viz. that the preservation of internal brightness, a
quality compatible with various methods, has had more to
do with the splendour and durability of finely coloured pic-
tures than any vehicle. The observations that follow are
therefore merely intended to show how far the older written
authorities on this subject agree with the results of modern
investigation, without at all assuming that the old methods,
if known, need be implicitly followed .
On a careful examination of the earlier pictures, it is said

* "Trattato," &c . p. 191 , the rest of the passage, it must be admitted,

abounds with absurdities.
400 NOTES .

that a resinous substance appears to have been mingled with

the colours together with the oil ; that the fracture of the
indurated pigment is shining, and that the surface resists the
ordinary solvents. * This admixture of resinous solutions or
varnishes with the solid colours is not alluded to, as far as
we have seen, by any of the writers on Italian practice, but
as the method corresponds with that now prevalent in
England, the above hypothesis is not likely to be objected to
for the present .
Various local circumstances and relations might seem to
warrant the supposition that the Venetian painters used
resinous substances. An important branch of commerce
between the mountains of Friuli and Venice still consists in
the turpentine or fir-resin .† Similar substances produced
from various trees, and known under the common name of
balsams, were imported from the East through Venice, for
general use, before the American balsams§ in some degree
superseded them ; and a Venetian painter, Marco Boschini,
in his description of the Archipelago , does not omit to speak
of the abundance of mastic produced in the island of Scio.
The testimonies, direct or indirect, against the employ-

* See " Marcucci Saggio Analitico-chimico sopra i colori," &c . Rome, 1816 ,
and "Taylor's Translation of Merimée on Oil-painting," London , 1839. The
last-named work contains much useful information.
Italian writers of the 16th century speak of three kinds. Cardanus says,
that of the abies was esteemed most, that of the larix next, and that of the
picea least. The resin extracted by incision from the last (the pinus abies
Linnæi) is known by the name of Burgundy pitch ; when extracted by fire it
is black. The three varieties occur in Italian treatises on art, under the
names of oglio di abezzo, trementina and pece Greca.
The concrete balsam benzoe, called by the Italians beluzino, and bel-
zoino, is sometimes spoken of as a varnish.
§ Marcucci supposes that balsam of copaiba was mixed with the pigments
by the (later) Venetians.
"L'Archipelago con tutte le Isole," Ven. 1658. The incidental notices
of the remains of antiquity in this work would be curious and important if
they could be relied on. In describing the island of Samos, for instance, the
author asserts that the temple of Juno was in tolerable preservation, and that
the statue was still there.
 NOTES. 401

mingle ment of any such substances by the Venetian painters, in the

cture solid part of their work, seem, notwithstanding, very con-
e resists2 clusive ; we begin with the writer just named . In his prin-
solutans cipal composition, a poem * describing the practice and the
10. 25 ra productions of the Venetian painters, Boschini speaks of
certain colours which they shunned, and adds : — In like
evaler a manner (they avoided) shining liquids and varnishes, which
objected: I should rather call lackers ; for the surface of flesh, if
natural and unadorned, assuredly does not shine, nature
Gt seemT speaks as to this plainly. " After alluding to the possible
ers alteration of this natural appearance by means of cosmetics,
he continues : " Foreign artists set such great store by these
varnishes, that a shining surface seems to them the only de-
proda sirable quality in art. What trash it is they prize ! fir- resin ,
Gable ! mastic, and sandarach, and larch-resin (not to say treacle),
nice.i stuff fit to polish boots. If those great painters of ours

deta had to represent armour, a gold vase, a mirror, or anything

of the kind, they made it shine with (simple) colours. "§
Bosch
This writer so frequently alludes to the Flemish painters,
osped
of whose great reputation he sometimes seems jealous, that
the above strong expression of opinion may have been
mplar
pointed at them. On the other hand it is to be observed
that the term forestieri, strangers, does not necessarily mean
9. To transalpine foreigners , but includes those Italians who were

* "La Carta del Navegar Pitoresco," Ven . 1660. It is in the Venetian

ofthe dialect.
sahes Inveriadure (invetriature) , literally the glazing applied to earthenware.
"O de che strazze se fan cavedal !
2%

D'ogio d'avezzo, mastici e sandraca ;

E trementina (per no'dir triaca)
Robe, che ilustrerave ogni stival ."-p. 338.
The alliteration of the words trementina and triaca is of course lost in a
geats translation.
§ "I li ha fati straluser co' i colori." Boschini was at least constant in his
tices opinion. In the second edition of his " Ricche Minere della Pittura Venez-
ntif iana," which appeared fourteen years after the publication of his poem, he
the repeats that the Venetian painters avoided some colours in flesh " e similmente
bat i lustri e le vernici."
2 D
 402 NOTES .

not of the Venetian state. * The directions given by

Raphael Borghini , † and after him by Armenini ,‡ respect
ing the use and preparation of varnishes made from the very
materials in question, may thus have been comprehended in
the censure, especially as some of these recipes were copied
and republished in Venice by Bisagno, § in 1642—that is,
only six years before Boschini's poem appeared.
Ridolfi's Lives of the Venetian Painters|| ( 1648) may be
mentioned with the two last. His only observation respect
ing the vehicle is, that Giovanni Bellini, after introducing
himself by an artifice into the painting-room of Antonello
da Messina, saw that painter dip his brush from time to
time in linseed oil. This story, related about two hun
dred years after the supposed event, is certainly not to be
adduced as very striking evidence in any way.¶
Among the next writers, in order of time prior to Bisagno,
may be mentioned Canepario** ( 1619 ) . His work, " De
Atramentis" contains a variety of recipes for different pur
poses one chapter, De atramentis diversicoloribus, has a
more direct reference to painting. His observations under
this head are by no means confined to the preparation of
transparent colours, but he says little on the subject of
* Thus, in the introduction to the " Ricche Minere," Boschini calls the
Milanese, Florentine, Lombard , and Bolognese painters, forestieri.
"Il Riposo," Firenze , 1584.
" De' Veri Precetti della Pittura," Ravenna, 1587 .
§ "Trattato della Pittura fondato nell' autorità di molti eccellenti in questa
professione." Venezia, 1642. Bisagno remarks in his preface, that the books
on art were few, and that painters were in the habit of keeping them secret.
He acknowledges that he has availed himself of the labours of others, but
without mentioning his sources : some passages are copied from Lomazzo.
He, however, lays claim to some original observations, and says he had seen
much and discoursed with many excellent painters.
" Le Meraviglie dell' Arte," Venezia, 1648.
¶It has been conjectured by some that this story proved the immixture of
varnishes with the colours, and that the oil was only used to dilute them.
The epitaph on Antonello da Messina which existed in Vasari's time, alludes
to his having mixed the colours with oil.
** 66'Petri Mariæ Caneparii De Atramentis cujuscumque generis," Venet.
1619. It was republished at Rotterdam in 1718.
 NOTES . 403

varnishes. After describing a mode of preserving white of

egg, he says, 66 Others are accustomed to mix colours in
liquid varnish and linseed, or nut-oil ; for a liquid and oily
varnish binds the (different layers of ) colours better toge-
ther, and thus forms a very fit glazing material. "* On the
subject of oils he observes, that linseed oil was in great re-
quest among painters ; who, however, were of opinion that
nut-oil excelled it " in giving brilliancy to pictures, in pre-
serving them better, and in rendering the colours more
vivid ."†
Lomazzo (a Milanese) says nothing on the subject of
vehicles in his principal work, but in his " Idea del Tempio
della Pittura, " he speaks of grinding the colours " in nut-
oil, and spike-oil, and other things," the " and" here evidently
means or, and by " other things" we are perhaps to under-
stand other oils, poppy oil, drying oils, &c.
The directions of Raphael Borghini and Vasari § cannot
certainly be considered conclusive as to the practice of the
Venetians, but they are very clear on the subject of varnish.
These writers may be considered the earliest Italian autho-
rities who have entered much into practical methods. In
the few observations on the subject of vehicles in Leonardo
da Vinci's treatise, "there is nothing," as M. Merimée ob-
serves, " to show that he was in the habit of mixing varnish
with his colours." Cennini says but little on the subject
*"Ita quod magis ex hiis evadit atramentum picturæ summopere idoneum ."
Thus, ifatramentum is to be understood , as usual, to mean a glazing colour, the
passage can only refer to the immixture of varnish with the transparent colours
applied last in order.
In a passage that follows respecting the mode of extracting nut-oil,
Caneparius appears to mistranslate Galen, c. 7-" De Simplicium Medica-
mentorum facultatibus." The observations of Galen on this subject, and on
the drying property of linseed, may have given the first hint to the inventors of
oil-painting. The custom of dating the origin of this art from Van Eyck is
like that of dating the commencement of modern painting from Cimabue.
The improver is often assumed to be the inventor.
Milan, 1590.
The particulars here alluded to are to be found in the first edition of
Vasari (1550) as well as the second. -v. i. c. 21 , &c.
2D2
404 NOTES .

of oil - painting ; Leon Battista Alberti is theoretical rather

than practical, and the published extracts of Lorenzo Ghi-
berti's MS . chiefly relate to sculpture.
Borghini and Vasari agree in recommending nut-oil in
preference to linseed-oil ; both recommend adding varnish
to the colours in painting on walls in oil , " because the
work does not then require to be varnished afterwards, "
but in the ordinary modes of painting on panel or cloth,
the varnish is omitted . Borghini expressly says , that oil
alone (senza più ) is to be employed ; he also recommends
a very sparing use of it.
The treatise of Armenini (1587) was published at
Ravenna, and he himself was of Faenza, so that his autho-
rity, again, cannot be considered decisive as to the Venetian
practice. After all, he recommends the addition of " com-
mon varnish" only for the ground or preparation, as a con-
solidating medium, for the glazing colours, and for those
dark pigments which are slow in drying. Many of his
directions are copied from the writers last named ; the re-
cipes for varnishes, in particular, are to be found in Bor-
ghini. Christoforo Sorte* ( 1580) briefly alludes to the
subject in question . After speaking of the methods of dis-
temper, he observes that the same colours may be used in
oil, except that instead of mixing them with size, they are
mixed on the palette with nut-oil , or (if slow in drying) with
boiled linseed -oil : he does not mention varnish. The
Italian writers next in order are earlier than Vasari, and
may therefore be considered original, but they are all very
concise.

* " Osservazioni nella Pittura." In Venezia, 1580. Sorte, who, it appears,

was a native of Verona, had worked in his youth with Giulio Romano, at
Mantua, and communicates the methods taught him by that painter, for giving
the true effects of perspective in compositions of figures. He is, perhaps, the
earliest who describes the process of water-colour painting as distinguished
from distemper and as adapted to landscape, if the art he describes deserves
the name.
 NOTES . 405

The treatise of Michael Angelo Biondo * ( 1549), re-

markable for its historical mistakes, is not without interest
in other respects. The list of colours he gives is, in all
probability, a catalogue of those in general use in Venice at
the period he wrote. With regard to the vehicle, he merely
mentions oil and size as the mediums for the two distinct
methods of oil-painting and distemper, and does not speak
of varnish. The passages in the Dialogue of Donit ( 1549),
which relate to the subject in question, are to the same
effect. " In colouring in oil, " he observes, " the most
brilliant colours (that we see in pictures) are prepared by
merely mixing them with the end of a knife on the palette ."
Speaking of the perishable nature of works in oil-painting
as compared with sculpture, he says, that the plaster of
Paris (gesso) and mastic, with other ingredients of which
the ground is prepared, are liable to decay, &c.; and else-
where, in comparing painting in general with mosaic, that
in the former the colours " must of necessity be mixed with
various things, such as oils, gums , white or yolk of egg, and
juice of figs, all which tend to impair the beauty of the tints."
This catalogue of vehicles is derived from all kinds of paint-
ing to enforce the argument, and is by no means to be
understood as belonging to one and the same method .
An interesting little work, still in the form of a dialogue
(Fabio and Lauro), appeared a year earlier ; the author,
Paolo Pino, was a Venetian painter. In speaking of the
practical methods Fabio observes, as usual, that oil - painting
is of all modes of imitation the most perfect , but his reasons
for this opinion seem to have a reference to the Venetian

* "Della nobilissima Pittura e sua Arte," Venezia, 1549. Biondo is so

ignorant as to attribute the Last Supper, by Leonardo da Vinci, to Mantegna.
" Disegno del Doni ," in Venezia, 1549.
" Dialogo di Pittura ," Venezia, 1548. Pino, in enumerating the cele-
brated contemporary artists, does not include Paul Veronese, for a very
obvious reason, that painter being at the time only about 17 years of age.
Sorte, who wrote thirty years later, mentions " l'eccellente Messer Paulino
nostro," alone.
406 NOTES .

practice of going over the work repeatedly. Lauro asks

whether it is not possible to paint in oil on the dry wall, as
Sebastian del Piombo did. Fabio answers, " the work

cannot last, for the solidity of the plaster is impenetrable,

and the colours, whether in oil or distemper, cannot pass
the surface." This might seem to warrant the inference
that absorbent grounds were prepared for oil-painting, but
there are proofs enough that resins as well as oil were used
with the gesso to make the preparation compact. See Doni,
Armenini, &c. This writer, again, does not speak of var
nish. These appear to be the chief Venetian and Italian
authorities* of the sixteenth and part of the following cen
tury ; and although Boschini wrote latest, he appears to have
had his information from good sources, and more than once
distinctly quotes Palma Giovane.
In all these instances it will be seen that there is no allu
sion to the immixture of varnishes with the solid colours,
except in painting on walls in oil, and that the processes of
distemper and oil are always considered as separate arts. +

* The Dialogues of Lodovico Dolce, and various other works, are not re
ferred to here, as they contain nothing on the subject in question. The latest
authority at all connected with the traditions of Venetian practice, is a certain
Giambatista Volpato, of Bassano : he died in 1706 , and had been intimate
with Ridolfi. The only circumstance he has transmitted relating to practical
details is that Giacomo Bassan, in retouching on a dry surface, sometimes
adopted a method commonly practised, he says, by Paul Veronese (and com
monly practised still), namely, that of dipping his brush in spirits of turpen
tine ; at other times he oiled out the surface in the usual manner. Volpato
left a MS . which was announced for publication in Vicenza in 1685 , but it
never appeared ; it, however, afterwards formed the ground-work of Verci's
" Notizie intorno alla Vita e alle Opere de' Pittori di Bassano." Venezia,
1775. See also " Lettera di Giambatista Roberti sopra Giacomo da Ponte ,"
Lugano , 1777. Another MS . by Natale Melchiori , of about the same date, is
preserved at Treviso and Castel Franco : it abounds with historical mistakes ;
the author says, for instance, that the Pietro Martyre was begun by Gior
gione and finished by Titian. The recipes for varnishes and colours are very
numerous, but they are mostly copied from earlier works.
That distemper was not very highly esteemed by the Venetians may be
inferred from the following observation of Pino :-" Il modo di colorir à
guazzo è imperfetto et più fragile et à me non diletta onde lasciamolo all'
 NOTES. 407

On the other hand, the prohibition of Boschini cannot be

understood to be universal , for it is quite certain that the
Venetians varnished their pictures when done. * After
Titian had finished his whole- length portrait of Pope Paul
III. it was placed in the sun to be varnished . † Again , in
the archives of the church of S. Niccolo at Treviso a sum
is noted ( Sept. 21 , 1521 ) , " per far la vernise da invernisar
la Pala dell' altar grando, " and the same day a second entry
appears of a payment to a painter, " per esser venuto a dar
la vernise alla Pala, " & c.‡ It is to be observed that in
both these cases the pictures were varnished as soon as
done ; the varnish employed was perhaps the thin com-
pound of naphtha (oglio di sasso) and melted turpentine
(oglio d'abezzo) , described by Borghini, and after him by
Armenini the last-named writer remarks that he had seen

oltremontani i quali sono privi della vera via." It is, however, certain that
the Venetians sometimes painted in this style, and Volpato mentions several
works of the kind by Bassan, but he never hints that he began his oil pictures
in distemper.
* Boschini says, that the Venetians (he especially means Titian) rendered
their pictures sparkling by finally touching on a dry surface (à secco) . The
absence of varnish in the solid colours , the retouching with spirit of turpen-
tine, and even à secco, all suppose a dull surface, which would require var-
nish. The latter method, alluded to by Boschini , was an exception to the
general practice, and not likely to be followed on account of its difficulty.
Carlo Maratti, on the authority of Palomino, used to say, " He must be a
skilful painter who can retouch without oiling out."
See a letter by Francesco Bocchi, and another by Vasari, in the " Lettere
Pittoriche" of Bottari. The circumstance is mentioned incidentally ; the
point chiefly dwelt on is, that some persons who passed were deceived, and
bowed to the picture, supposing it to be the pope.
Federici, " Memorie Trevigiane," Venezia, 1803. The altar-piece of
S. Niccolo at Treviso is attributed, in the document alluded to, to Fra Marco
Pensabene, a name unknown ; the painting is so excellent as to have been
thought worthy of Sebastian del Piombo : for this opinion, however, there are no
historical grounds. It was begun in 1520, but before it was quite finished the
painter, whoever he was, absconded : it was therefore completed by another.
§ Titian's stay in Rome was short, and with respect to the Treviso altar-
piece, a week or two only, at most, can have elapsed between the completion
and the varnishing. Cennini, who recommends delaying a year at least be-
fore varnishing, speaks of pictures in distemper.
 408 NOTES .

this varnish used by the best painters in Lombardy, and

had heard that it was preferred by Correggio. The conse
quence of this immediate varnishing may have been that the
warm resinous liquid, whatever it was, became united with
the colours, and thus at a future time the pigment may have
acquired a consistency capable of resisting the ordinary sol
vents. Not only was the surface of the picture required to
be warm , but the varnish was applied soon after it was taken
from the fire.*
Many of the treatises above quoted contain directions for
making the colours dry : † some of these recipes, and many
in addition, are to be found in Palomino, who, however de
fective as an historian, has left very copious practical
details, evidently of ancient date . His drying recipes are
numerous, and although sugar of lead does not appear, car
denillo (verdigris), which is perhaps as objectionable, is
admitted to be the best of all dryers. It may excite some
surprise that the Spanish painters should have bestowed so
much attention on this subject in a climate like theirs, but
the rapidity of their execution must have often required
such an assistance.§
One circumstance alluded to by Palomino, in his very
minute practical directions, deserves to be mentioned . After

* See Borghini , Armenini, their Venetian copyist Bisagno, and Palomino .

The last-named writer, though of another school and much more modern, was
evidently well acquainted with the ancient methods : he says, “ Se advierte
que siempre que se huviere de barnizar alguna cosa conviene que la pintura y
el barniz estén calientes."-El Museo Pictorico, v. ii.
† Burnt alum, one of the ingredients recommended, might perhaps account
for a shining fracture in the indurated pigment in some old pictures.
Of the earlier Spanish writers Pacheco may be mentioned next to Palo
mino as containing most practical information. Carducho, De Butron, and
others, seldom descend to such details. Palomino contains all the directions
of Pacheco, and many in addition.
See Cean Bermudez, " Sobre la Escuela Sevillana," Cadiz, 1806. The
same reasons induced the later Venetian machinists to paint on dark grounds,
and to make use of (drying) oil in excess. See Zanetti, Della Pittura Vene
ziana, 1. iv.
 NOTES. 409

saying what colours should be preserved in their saucers

under water, and what colours should be merely covered
with oiled paper because the water injures them, he pro
ceeds to communicate " a curious mode of preserving oil
colours," and of transporting them from place to place.
The important secret is to tie them in bladders, the mode
of doing which he enters into with great minuteness , as if
the invention was recent. It is true, Christoforo Sorte, in
describing his practice in water- colour drawing, says he was
in the habit of preserving a certain vegetable green with
gum-water in a bladder ; but as the method was obviously
new to Palomino, there seems sufficient reason to believe
that oil - colours, when once ground, had, up to his time, been
kept in saucers and preserved under water. * Among the
items of expense in the Treviso document before alluded
to, we find " a pan and saucers for the painters." This is
in accordance with Cennini's directions, and the same sys
tem appears to have been followed till after 1700. ‡
The Flemish accounts of the early practice of oil- painting
are all later than Vasari. Van Mander, in correcting the
Italian historian in his dates, still follows his narrative in
other respects verbatim . If Vasari's story is to be accepted
as true , it might be inferred that the Flemish secret con
sisted in an oil varnish like copal.§ Vasari says, that Van

* Borghini, in describing the method of making a gold-size (the same as

Cennini's), speaks of boiling the " buccie de' colori" in oil ; this only means
the skin or pellicle of the colour itself-in fact, he proceeds to say that they
dissolve in boiling. Vasari, in describing the same process, uses the expres
sion " colori seccaticci."
" Maggio 4 ( 1520) Per un cadin (catino) per depentori. Per scudellini
per li depentori.” —Mem. Trev., vol. i . p. 131. Pungileoni ( " Memorie Isto
riche di Antonio Allegri") quotes a note of expenses relating to two oil-pictures
by Paolo Gianotti ; among the items we find " colori, telari, et brocchette.”—
vol. ii. p . 75.
Salmon, in his " Polygraphice" ( 1701) , gives the following direction :
"Oyl colors, if not presently used, will have a skin grow over them, to pre
vent which put them into a glass, and put the glass three or four inches under
water," & c.
This varnish appears to have been known some centuries before Van
Eyck's time, but he may have been the first to mix it with the colours.
410 NOTES .

Eyck boiled the oils with other ingredients ; that the colours,
when mixed with this kind of oil, had a very firm con
sistence ; that the surface of the pictures so executed had a
lustre, so that they needed no varnish when done ; and that
the colours were in no danger from water. *
Certain colours, as is well known , if mixed with oil alone,
may be washed off after a considerable time. Leonardo
da Vinci remarks, that verdigris may be thus removed.
Carmine, Palomino observes, may be washed off after six
years. It is on this account the Italian writers recommend
the use of varnish with certain colours, and it appears the
Venetians, and perhaps the Italians generally, employed it
solely in such cases. But it is somewhat extraordinary that
Vasari should teach a mode of painting in oil so different
in its results (inasmuch as the work thus required varnish
at last) from the Flemish method which he so much ex
tols -a method which he says the Italians long endeavoured
to find out in vain. If they knew it , it is evident, assuming
his account to be correct, that they did not practice it.

NOTE W.- Par. 608.

In the second volume Goethe gives the nomenclature of

the Greeks and Romans at some length. The general no
tions of the ancients with regard to colours are thus de
scribed :-" The ancients derive all colours from white and
black, from light and darkness . They say, all colours are
between white and black, and are mixed out of these. We
must not, however, suppose that they understand by this a
mere atomic mixture, although they occasionally use the
word us; for in the remarkable passages, where they
wish to express a kind of reciprocal (dynamic) action of the
two contrasting principles, they employ the words xpãos,
union, σúyxρios, combination ; thus , again, the mutual in
fluence of light and darkness, and of colours among each

* See Vasari, Life of Antonello da Messina.

See Note on Par. 177.
 NOTES . 411

other, is described by the word xepávvvoda , an expression of

similar import.
"The varieties of colours are differently enumerated ;
some mention seven, others twelve, but without giving the
complete list. From a consideration of the terminology
both of the Greeks and Romans, it appears that they some
times employed general for specific terms, and vice versa.
"Their denominations of colours are not permanently and
precisely defined, but mutable and fluctuating, for they are
employed even with regard to similar colours both on the
plus and minus side . Their yellow, on the one hand, in
clines to red, on the other to blue ; the blue is sometimes
green, sometimes red ; the red is at one time yellow, at
another blue. Pure red (purpur) fluctuates between warm
red and blue, sometimes inclining to scarlet, sometimes to
violet.
" Thus the ancients not only seem to have looked upon
colour as a mutable and fleeting quality, but appear to have
had a presentiment of the (physical and chemical ) effects
of augmentation and re-action , In speaking of colours
they make use of expressions which indicate this knowledge ;
they make yellow redden, because its augmentation tends
to red ; they make red become yellow, for it often returns
thus to its origin.
" The hues thus specified undergo new modifications.
The colours arrested at a given point are attenuated by a
stronger light darkened by a shadow, nay, deepened and
condensed in themselves. For the gradations which thus
arise the name of the species only is often given, but the
more generic terms are also employed . Every colour, of
whatever kind, can, according to the same view, be multi
plied into itself, condensed, enriched, and will in conse
quence appear more or less dark. The ancients called
colour in this state," &c. Then follow the designations of
general states of colour and those of specific hues.
Another essay on the notions of the ancients respecting
 412 NOTES .

the origin and nature of colour generally, shows how nearly

Goethe himself has followed in the same track. The
dilating effect of light objects, the action and reaction of the
retina, the coloured after-image, the general law of contrast,
the effect of semi-transparent mediums in producing warm
or cold colours as they are interposed before a dark or light
background-all this is either distinctly expressed or hinted
66
at ; but," continues Goethe, " how a single element
divides itself into two , remained a secret for them. They
knew the nature of the magnet, in amber, only as attraction ;
polarity was not yet distinctly evident to them. And in
very modern times have we not found that scientific men
have still given their almost exclusive attention to attraction,
and considered the immediately excited repulsion only as a
mere after-action ?"
An essay on the Painting ofthe Ancients* was contributed
by Heinrich Meyer.

NOTE X.- Par . 670 .

This agrees with the general recommendation so often

given by high authorities in art, to avoid a tinted look in the
colour of flesh. The great example of Rubens, whose
practice was sometimes an exception to this, may however
show that no rule of art is to be blindly or exclusively
adhered to . Reynolds, nevertheless , in the midst of his
admiration for this great painter, considered the example
dangerous, and more than once expresses himself to this
effect, observing on one occasion that Rubens, like Baroccio,
is sometimes open to the criticism made on an ancient
painter, namely, that his figures looked as if they fed on
roses.
Lodovico Dolce, who is supposed to have given the vivá
voce precepts of Titian in his Dialogue , † makes Aretino

* Vol . ii. p. 69 , first edition.

"Dialogo della Pittura, intitolato l'Aretino ." It was first published at
Venice in 1557 ; about twenty years before Titian's death. In the dedication
 NOTES . 413

say : " I would generally banish from my pictures those

vermilion cheeks with coral lips ; for faces thus treated look
like masks . Propertius , reproving his Cynthia for using
cosmetics , desires that her complexion might exhibit the
simplicity and purity of colour which is seen in the works of
Apelles ."
Those who have written on the practice of painting have
always recommended the use of few colours for flesh .
Reynolds and others quote even ancient authorities as re-
corded by Pliny, and Boschini gives several descriptions of
the method of the Venetians, and particularly of Titian, to
the same effect. " They used," he says, 66 earths more than
any other colour, and at the utmost only added a little ver-
milion, minium , and lake, abhorring as a pestilence biadetti,
gialli santi, smaltini, verdi-azzurri, giallolini . " * Else-
where he says , t " Earths should be used rather than other
colours :" after repeating the above prohibited list he adds,
" I speak of the imitation of flesh, for in other things every
colour is good ;" again, " Our great Titian used to say that
he who wishes to be a painter should be acquainted with
three colours, white, black, and red ."+ Assuming this

to the senator Loredano, Lodovico Dolce eulogises the work, which he would
hardly have done if it had been entirely his own : again, the supposition that
it may have been suggested by Aretino, would be equally conclusive, coupled
with internal evidence, as to the original source.
* Introduction to the " Ricche Minere della Pittura Veneziana," Venezia,
1674. The Italian annotators on older works on painting are sometimes at a
loss to find modern terms equivalent to the obsolete names of pigments. (See
" Antologia dell'Arte Pittorica.") The colours now in use corresponding with
Boschini's list, are probably yellow lakes, smalt, verditer, and Naples yellow.
Boschini often censures the practice of other schools, and in this emphatic
condemnation he seems to have had an eye to certain precepts in Lomazzo,
and perhaps, even in Leonardo da Vinci, who, on one occasion, recommends
Naples yellow, lake, and white for flesh . The Venetian writer often speaks,
too, in no measured terms of certain Flemish pictures, probably because they
appeared to him too tinted.
+ "La Carta del Navegar Pitoresco," p. 338 .
Ib. p. 341. In describing Titian's actual practice (" Ricche Minere”),
he, however, adds yellow (ochre) . The red is also particularised , viz. , the
common terra rossa.
414 NOTES .

account to be a little exaggerated, it is still to be observed

that the monotony to which the use of few colours would
seem to tend, is prevented by the nature of the Venetian
process, which was sufficiently conformable to Goethe's
doctrine ; the gradations being multiplied, and the effect of
the colours heightened by using them as semi-opaque me-
diums. Immediately after the passage last quoted we read,
" He also gave this true precept, that to produce a lively
colouring in flesh it is not possible to finish at once. "* As
these particulars may not be known to all, we add some
further abridged extracts explaining the order and methods
of these different operations .
" The Venetian painters," says this writer, " after
having drawn in their subject, got in the masses with very
solid colour, without making use of nature or statues. Their
great object in this stage of their work was to distinguish
the advancing and retiring portions, that the figures might
be relieved by means of chiaro-scuro- one of the most im-
portant departments of colour and form, and indeed of in-
vention. Having decided on their scheme of effect, when
this preparation was dry, they consulted nature and the
antique ; not servilely, but with the aid of a few lines on
paper (quattro segni in carta) they corrected their figures
without any other model. Then returning to their brushes,
they began to paint smartly on this preparation, producing
the colour of flesh. " The passage before quoted follows,
stating that they used earths chiefly, that they carefully
avoided certain colours, " and likewise varnishes and what-
ever produces a shining surface.‡ When this second painting
was dry, they proceeded to scumble over this or that figure
with a low tint to make the one next it come forward, giving
another, at the same time, an additional light-for example,
* High examples here again prove that the opposite system may attain
results quite as successful.
+ Introduction to the " Ricche Minere."
See Note to Par. 555. Here again, assuming the description to be cor-
rect, high authorities might be opposed to the Venetians.
 NOTES. 415

on a head, a hand, or a foot, thus detaching them , so to speak,

from the canvas." (Tintoret's Prigionia di S. Rocco is here
quoted.) " By thus still multiplying these well -understood
retouchings where required, on the dry surface, (a secco)
they reduced the whole to harmony. In this operation they
took care not to cover entire figures, but rather went on
gemming them (gioielandole) with vigorous touches . In
the shadows, too, they infused vigour frequently by glazing
with asphaltum, always leaving great masses in middle-tint,
with many darks, in addition to the partial glazings, and
few lights. "
The introduction to the subject of Venetian colouring, in
the poem by the same author, is also worth transcribing, but
as the style is quaint and very concise, a translation is neces-
sarily a paraphrase. *
66
The art of colouring has the imitation of qualities for
its object ; not all qualities, but those secondary ones which
are appreciable by the sense of sight. The eye especially
sees colours, the imitation of nature in painting is therefore
justly called colouring ; but the painter arrives at his end
by indirect means . He gives the varieties of tone in masses ;†

* The following quatrain may serve as a specimen ; the author is speaking

ofthe importance of the colour of flesh as conducive to picturesque effect :—
Importa el nudo ; e come ben l'importa !
Un quadro senza nudo è come aponto
Un disnar senza pan, se ben ghe zonto,
Per più delicia, confetura e torta.” —p. 346.
In his preface he anticipates, and thus answers the objections to his Venetian
dialect " Mi, che son Venetian in Venetia e che parlo de' Pitori Venetiani
hò da andarme a stravestir ? Guarda el Cielo."
The word Macchia, literally a blot, is generally used by Italian writers,
by Vasari for instance, for the local colour. Boschini understands by it the
relative depth of tones rather than the mere difference of hue. " By macchia,"
he says, “ I understand that treatment by which the figures are distinguished
from each other by different tones lighter or darker." - La Carta del
Navegar, p. 328. Elsewhere, " Colouring (as practised by the Venetians)
comprehends both the macchia and drawing ;" (p. 300) that is, comprehends
the gradations of light and dark in objects, and the parts of objects, and con-
sequently, their essential form. " The macchia," he adds, " is the effect of
practice, and is dictated by the knowledge of what is requisite for effect."
416 NOTES .

he smartly impinges lights, he clothes his preparation with

more delicate local hues, he unites, he glazes thus every
thing depends on the method, on the process. For if we
look at colour abstractedly, the most positive may be called
the most beautiful, but if we keep the end of imitation in
view, this shallow conclusion falls to the ground. The
refined Venetian manner is very different from mere direct,
sedulous imitation. Every one who has a good eye may
arrive at such results, but to attain the manner of Paolo ,
of Bassan, of Palma, Tintoret, or Titian, is a very different
undertaking. " *
The effects of semi-transparent mediums in some natural
productions seem alluded to in the following passage
" Nature sometimes accidentally imitates figures in stones
and other substances, and although they are necessarily in
complete in form, yet the principle of effect (depth ) re
sembles the Venetian practice." In a passage that follows
there appears to be an allusion to the production of the
atmospheric colours by semi-transparent mediums. †

NOTE Y.- Par. 672.

The author's conclusion here is unsatisfactory, for the

colour of the black races may be considered at least quite
as negative as that of Europeans. It would be safer to say
that the white skin is more beautiful than the black, because
it is more capable of indications of life, and indications of
emotion. A degree of light which would fail to exhibit the
finer varieties of form on a dark surface, would be sufficient
to display them on a light one ; and the delicate mantlings

" Ma l'arivar a la maniera, al trato

(Verbi gratia) de Paulo, del Bassan,
Del Vechio, Tentoreto, e di Tician,
Per Dio, l'è cosa da deventar mato." -p. 294 , 297.
The traces of the Aristotelian theory are quite as apparent in Boschini
as in the other Italian writers on art ; but as he wrote in the seventeenth
century, his authority in this respect is only important as an indication of the
earlier prevalence of the doctrine.
 NOTES . 417

ration vo of colour, whether the result of action or emotion, are more

perceptible for the same reason.
Firth
Theat NOTE Z.- Par. 690.
mitate .
The author appears to mean that a degree of brightness
ind. I
which the organ can bear at all, must of necessity be re-
ereLe
moved from dazzling, white light. The slightest tinge of
I eresi
colour to this brightness, implies that it is seen through a
ofP
medium , and thus, in painting, the lightest, whitest surface
should partake of the quality of depth . Goethe's view here
again accords, it must be admitted, with the practice of the
De best colourists, and with the precepts of the highest autho-
passer rities.--See Note C.

ssarira NOTE A A. - Par. 732.

apti. »
atMor Ample details respecting the opinions of Louis Bertrand
Castel, a Jesuit, are given in the historical part . The co-
on t
incidence of some of his views with those of Goethe is often
apparent he objects, for instance, to the arbitrary selection
of the Newtonian spectrum ; observing that the colours
change with every change of distance between the prism
fort
and the recipient surface . - Farbenl. vol . ii . p . 527. Jeremias
ast ju Friedrich Gülich was a dyer in the neighbourhood of
er to s Stutgardt : he published an elaborate work on the technical
beca details of his own pursuit.- Farbenl. vol . ii . p. 630.
ations al
ibitthe NOTE B B.- Par. 748.
fficer
g Goethe, in his account of Castel, suppresses the learned
antin
Jesuit's attempt at colorific music (the clavecin oculaire) ,
founded on the Newtonian doctrine. Castel was compli-
mented, perhaps ironically, on having been the first to re-
mark that there were but three principal colours . In
n asserting his claim to the discovery, he admits that there is
Boschi
nothing new. In fact, the notion of three colours is to be
nofthe found in Aristotle ; for that philosopher enumerates no
2 E
418 NOTES .

more in speaking of the rainbow,* and Seneca calls them by

their right names .† Compare with Dante, Parad . c. 33.
The relation between colours and sounds is in like manner
adverted to by Aristotle ; he says-" It is possible that
colours may stand in relation to each other in the same
manner as concords in music, for the colours which are (to
each other) in proportions corresponding with the musical
concords , are those which appear to be the most agreeable. ” ‡
In the latter part of the 16th century, Arcimboldo, a
Milanese painter, invented a colorific music ; an account of
his principles and method will be found in a treatise on
painting which appeared about the same time. " Am-
maestrato dal qual ordine Mauro Cremonese dalla viola,
musico dell' Imperadore Ridolfo II . trovò sul gravicembalo
tutte quelle consonanze che dall' Arcimboldo erano segnate
coi colori sopra una carta. ” §

NOTE C C.- Par. 758.

The moral associations of colours have always been a

more favourite subject with poets than with painters. This
is to be traced to the materials and means of description as
distinguished from those of representation. An image is
more distinct for the mind when it is compared with some-
thing that resembles it. An object is more distinct for the
eye when it is compared with something that differs from it.
Association is the auxiliary in the one case, contrast in the

"De Meteor.," lib. 3, c. ii. and iv. He observes that this is the only
effect of colour which painters cannot imitate.
" De Ignib. cœlest. " The description of the prism by Seneca is another
instance of the truth of Castel's admission . The Roman philosopher's words
are-"Virgula solet fieri vitrea, stricta vel pluribus angulis in modo clavæ
tortuosæ ; hæc si ex transverso solem accipit colorem talem qualis in arcu
videri solet, reddit," &c.
"De Sensu et sensili."
" Il Figino, overo del Fine della Pittura," Mantova, 1591 , p . 249. An
account of the absurd invention of the same painter in composing figures of
flowers and animals, and even painting portraits in this way, to the great
delight of the emperor, will be found in the same work.
 NOTES . 419

other. The poet, of necessity, succeeds best in conveying

the impression of external things by the aid of analogous
rather than of opposite qualities : so far from losing their
Se
effect by this means, the images gain in distinctness. Com-
the
parisons that are utterly false and groundless never strike us
hare
as such if the great end is accomplished of placing the
thing described more vividly before the imagination . In
the common language of laudatory description the colour of
body. flesh is like snow mixed with vermilion : these are the words
used by Aretino in one of his letters in speaking of a figure
eatise ! of St. John , by Titian. Similar instances without end
-4
might be quoted from poets : even a contrast can only be
land strongly conveyed in description by another contrast that
icer' resembles it. On the other hand it would be easy to show
seg that whenever poets have attemped the painter's method of
direct contrast, the image has failed to be striking, for the
mind's eye cannot see the relation between two colours.
Under the same category of effect produced by association
s beer, may be classed the moral qualities in which poets have
s. T judiciously taken refuge when describing visible forms and
pikes colours, to avoid competition with the painters' elements,
MATE or rather to attain their end more completely. But a
h sca little examination would show that very pleasing moral
forthe associations may be connected with colours which would
fromi be far from agreeable to the eye. All light, positive co-
in the lours, light-green, light-purple, white, are pleasing to the
mind's eye, and no degree of dazzling splendour is offensive.
the The moment, however, we have to do with the actual sense
of vision, the susceptibility of the eye itself is to be consi-
dered, the law of comparison is reversed, colours become
striking by being opposed to what they are not, and their
inarea moral associations are not owing to the colours themselves,

Such as-
9.1
resof " Her beauty hangs upon the cheek of night,
e great Like a rich jewel in an Ethiop's ear.”
Romeo and Juliet.
2 E 2
 420 NOTES .

but to the modifications such colours undergo in consequence

of what surrounds them. This view, so naturally conse-
quent on the principles the author has himself arrived at,
appears to be overlooked in the chapter under considera-
tion , the remarks in which, in other respects, are acute and
ingenious .

NOTE D D. - Par. 849.

According to the usual acceptation of the term chiaro-

scuro in the artist world, it means not only the mutable
effects produced by light and shade, but also the permanent
differences in brightness and darkness which are owing to
the varieties of local colour.

NOTE E E. - Par. 855.

The mannered treatment of light and shade here alluded

to by the author is very seldom to be met with in the works
of the colourists ; the taste may have first arisen from the
use of plaster-casts, and was most prevalent in France and
Italy in the early part of the last century. Piazzetta repre-
sented it in Venice, Subleyras in Rome. In France
" Restout taught his pupils that a globe ought to be repre-
sented as a polyhedron. Greuze most implicitly adopted
the doctrine, and in practice showed that he considered the
round cheeks of a young girl or an infant as bodies cut into
facettes .""'*

NOTE F F. - Par. 859.

All this was no doubt suggested by Heinrich Meyer,

whose chief occupation in Rome, at one time, was making

* See Taylor's translation of Merimée on oil-painting, p . 27. Barry, in a

letter from Paris, speaks of Restout as the only painter who resembled the
earlier French masters : the manner in question is undoubtedly sometimes
very observable in Poussin. The English artist elsewhere speaks of the
"broad, happy manner of Subleyras." -Works, London, 1809.
 NOTES. 421

sepia drawings from sculpture (see Goethe's Italiänische

Reise) . It is hardly necessary to say that the observation
respecting the treatment of the surface in the antique sta
tues is very fanciful.

NOTE G G.- Par . 863.

This observation might have been suggested by the draw

ings of Claude, which, with the slightest means, exhibit an
harmonious balance of warm and cold .
Ad
RN

NOTE H H.- Par. 865.

The colouring of Paolo Uccello, according to Vasari's

account of him, was occasionally so remarkable that he
might perhaps have been fairly included among the in
stances of defective vision given by the author. His skill in
perspective, indicating an eye for gradation, may be also
C reckoned among the points of resemblance (see Par. 105).
ter
fin help NOTE II.- Par. 902.

A The quotation before given from Boschini shows that

BROA the method described by the author, and which is true with
la & regard to some of the Florentine painters, was not prac
Vies tised by the Venetians, for their first painting was very
solid. It agrees, however, with the manner of Rubens,
+9 many of whose works sufficiently corroborate the account
of his process given by Descamps. " In the early state of
Rubens's pictures, ” says that writer,* " everything appeared
like a thin wash ; but although he often made use of the
ground in producing his tones, the canvas was entirely
covered more or less with colour. " In this system of leaving
&.l.
the shadows transparent from the first, with the ground
shining through them , it would have been obviously destruc
tive of richness to use white mixed with the darks, the
B brightness, in fact, already existed underneath. Hence the
Name
" La Vie des Peintres Flamands," vol. i.
 422 NOTES .

well-known precept of Rubens to avoid white in the sha

dows, a precept, like many others, belonging to a particular
practice, and involving all the conditions of that practice. *
Scarmiglione, whose Aristotelian treatise on colour was
published in Germany when Rubens was three- and- twenty,
observes, " Painters, with consummate art, lock up the
bright colours with dark ones, and, on the other hand,
employ white, the poison of a picture, very sparingly.”
(Artificiosissimè pictores claros obscuris obsepiant et contra
¦
candido picturarum veneno summè parcentes, &c.)

NOTE K K.- Par. 903.

The practice here alluded to is more frequently observ

able in slight works by Paul Veronese. His ground was
often pure white, and in some of his works it is left as such.
Titian's white ground was covered with a light warm colour,
probably at first, and appears to have been similar to that
to which Armenini gives the preference, namely, " quella
che tira al color di carne chiarissima con un non so che di
fiammeggiante."†

The method he recommended for keeping the colours pure in the lights,
viz. to place the tints next each other unmixed, and then slightly to unite
them, may have degenerated to a methodical manner in the hands of his fol
lowers . Boschini, who speaks of Rubens himself with due reverence, and
is far from confounding him with his imitators, contrasts such a system
with that of the Venetians, and adds that Titian used to say, " Chi de imbra
tar colori teme, imbrata e machia si medemi. "-Carta del Navegar, p. 341 .
The poem of Boschini is in many respects polemical. He wrote at a time
when the Flemish painters, having adopted and modified the Venetian prin
ciples, threatened to supersede the Italian masters in the opinion of the
world. Their excellence, too, had all the charm of novelty, for in the seven
1 teenth century Venice produced no remarkable talent, and it was precisely
the age for her to boast of past glories. The contemptuous manner in which
Boschini speaks of the Flemish varnishes, of the fear of mixing tints, &c., is
thus always to be considered with reference to the time and circumstances.
So also his boasting that the Venetian masters painted without nature, which
be an exaggeration, is pointed at the Naturalisti, Caravaggio and his
may
followers, who copied nature literally.
+""Veri Precetti della Pittura," p. 125.

1
 NOTES . 423

NOTE L L.-Par. 919.

The notion which the author has here ventured to express

may have been suggested by the remarkable passage in the
last canto of Dante's " Paradiso"
" Nella profonda e chiara sussistenza,
Dell' alto lume parvemi tre giri
Di tre colori e d'una continenza," &c.

After the concluding paragraph the author inserts a letter

from a landscape- painter, Philipp Otto Runge, which is
intended to show that those who imitate nature may arrive
at principles analogous to those of the " Farbenlehre."

THE END.

London: Printed by W. CLOWES and SONS, Stamford Street.

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