The frame's "Greg" narrator talks to a CSA officer (Ubernarrator), gone to Mexico to fight for Maximilian, then shipwrecked in the Pacific. The officer found this manuscript in an aerial shipwreck.
The manuscript Unnamed Narrator who writes congealed bad Latin, but who expects interplanetary travel to soon fulfill his boyhood daydreams. His friends, Ubernarrator assumes, may still be alive. Ubernarrator assumes he left Earth for Mars in 1830!
Narrator spends pages setting up his apergy ship, named the Astronaut. He has a garden to refresh the air, with birds, all netted in. Were the birds emergency rations? He does not say.
Very detailed science fiction ascent, including a concept of weightlessness as extremely reduced weight. Appearance of Earth at distance, the star-stuffed reaches--brilliant stuff, however accurate or not.
"It would be mere waste of space and time were I to attempt anything like a journal of the weeks I spent in the solitude of this artificial planet. As matter of course, the monotony of a voyage through space is in general greater than that of a voyage across an ocean like the Atlantic, where no islands and few ships are to be encountered. It was necessary to be very frequently, if not constantly, on the look-out for possible incidents of interest in a journey so utterly novel through regions which the telescope can but imperfectly explore. It was difficult, therefore, to sit down to a book, or even to pursue any necessary occupation unconnected with the actual conduct of the vessel, with uninterrupted attention. My eyes, the only sense organs I could employ, were constantly on the alert ; but, of course, by far the greater portion of my time passed without a single new object or occasion of remark. That a journey so utterly without precedent or parallel, in which so little could be anticipated or provided for, through regions absolutely untraversed and very nearly unknown, should be monotonous, may seem strange. But in truth the noveltiesof the situation, such as they were, though intensely striking and interesting, were each in turn speedily examined, realised, and, so to speak, exhausted; and this once done, there was no greater occupation to the mind in the continuance of strange than in that of familiar scenery. The infinitude of surrounding blackness, filled as it were with points of light more or less brilliant, when once its effects had been scrutinised, and when nothing more remained to be noted, afforded certainly a more agreeable, but scarcely a more interesting or absorbing, outlook than the dead grey circle of sea, the dead grey hemisphere of cloud, which form the prospect from the deck of a packet in mid-Atlantic; while of change without or incident in the vessel herself there was, of course, infinitely less than is afforded in an ocean voyage by the variations of weather, not to mention the solace of human society."
Brilliant realization, no?
His discoveries include: Grey seas of Mars. Atmosphere for a satellite of Jupiter. Finds Earth 92 rather than 95 million miles from Sun--is this a careful postdating of later information into the historical? If so, it's really splendid. This is total geekness of detail, but perfect.
42 or so days to a Mars of mists and seas, forests, if thin atmosphere. No sense of lighter gravity on planet.
This borders on steampunk, in that the author, in 1880, is positing a more advanced science than his own in 1830, that accomplishes what he cannot, by an Unknown Principle. This is like us putting FTL flight in, say, 1918.
Original flora & fauna. This is NOT Utopia: they have violent politics and tragedy. Once down on the ground the Narrator gets involved with local politics and even marries. Really different than one comes to expect of period scientific romance, rather grittier than normal.
The first part is brilliant hard-science science fiction. The second part is scientific romance exploration, action, and adventure. Definitely worth a read!