Professor Thomas Nuttall, an inspiration for Stephen on board? Complete with the Captain responding something unprintable when the professor asked to stop the ship so he could explore an island
From Richard Henry Dana's memoir relating his 1834 voyage as a common merchant seaman, Two Years Before the Mast. His description of a botanist/ornithologist on board, and how the crew tries to make sense of him, really brings to mind Maturin.
>This passenger—the first and only one we had had, except to go from port to port, on the coast, was no one else than a gentleman whom I had known in my better days; and the last person I should have expected to have seen on the coast of California—Professor N——, of Cambridge. I had left him quietly seated in the chair of Botany and Ornithology, in Harvard University; and the next I saw of him, was strolling about San Diego beach, in a sailor's pea-jacket, with a wide straw hat, and barefooted, with his trowsers roiled up to his knees, picking up stones and shells. He had travelled overland to the North-west Coast, and come down in a small vessel to Monterey. There he learned that there was a ship at the leeward, about to sail for Boston; and, taking passage in the Pilgrim, which was then at Monterey, he came slowly down, visiting the intermediate ports, and examining the trees, plants, earths, birds, etc., and joined us at San Diego shortly before we sailed. The second mate of the Pilgrim told me that they had an old gentleman on board who knew me, and came from the college that I had been in.
>He could not recollect his name, but said he was a "sort of an oldish man," with white hair, and spent all his time in the bush, and along the beach, picking up flowers and shells, and such truck, and had a dozen boxes and barrels, full of them. I thought over everybody who would be likely to be there, but could fix upon no one; when, the next day, just as we were about to shove off from the beach, he came down to the boat, in the rig I have described, with his shoes in his hand, and his pockets full of specimens. I knew him at once, though I should not have been more surprised to have seen the Old South steeple shoot up from the hide-house. He probably had no less difficulty in recognizing me. As we left home about the same time, we had nothing to tell one another; and, owing to our different situations on board, I saw but little of him on the passage home. Sometimes, when I was at the wheel of a calm night, and the steering required no attention, and the officer of the watch was forward, he would come aft and hold a short yarn with me; but this was against the rules of the ship, as is, in fact, all intercourse between passengers and the crew. I was often amused to see the sailors puzzled to know what to make of him, and to hear their conjectures about him and his business. They were as much puzzled as our old sailmaker was with the captain's instruments in the cabin.
>He said there were three:—the chro-nometer, the chre-nometer, and the the-nometer. (Chronometer, barometer, and thermometer.) The Pilgrim's crew christened Mr. N. "Old Curious," from his zeal for curiosities, and some of them said that he was crazy, and that his friends let him go about and amuse himself in this way. Why else a rich man (sailors call every man rich who does not work with his hands, and wears a long coat and cravat) should leave a Christian country, and come to such a place as California, to pick up shells and stones, they could not understand. One of them, however, an old salt, who had seen something more of the world ashore, set all to rights, as he thought,—"Oh, 'vast there!—You don't know anything about them craft. I've seen them colleges, and know the ropes. They keep all such things for cur'osities, and study 'em, and have men a' purpose to go and get 'em. This old chap knows what he's about. He a'n't the child you take him for. He'll carry all these things to the college, and if they are better than any that they have had before, he'll be head of the college. Then, by-and-by, somebody else will go after some more, and if they beat him, he'll have to go again, or else give up his berth. That's the way they do it. This old covey knows the ropes. He has worked a traverse over 'em, and come 'way out here, where nobody's ever been afore, and where they'll never think of coming." This explanation satisfied Jack; and as it raised Mr. N.'s credit for capacity, and was near enough to the truth for common purposes, I did not disturb it.
And later upon sighting an unexplored island:
>This gave us a new start, and we were soon through our work, and on deck; and there lay the land, fair upon the larboard beam, and slowly edging away upon the quarter. All hands were busy looking at it—the captain and mates from the quarter-deck, the cook from his galley, and the sailors from the forecastle; and even Mr. N., the passenger, who had kept in his shell for nearly a month, and hardly been seen by anybody, and who we had almost forgotten was on board, came out like a butterfly, and was hopping round as bright as a bird.
>The land was the island of Staten Land, and, just to the eastward of Cape Horn; and a more desolate-looking spot I never wish to set eyes upon;—bare, broken, and girt with rocks and ice, with here and there, between the rocks and broken hillocks, a little stunted vegetation of shrubs. It was a place well suited to stand at the junction of the two oceans, beyond the reach of human cultivation, and encounter the blasts and snows of a perpetual winter. Yet, dismal as it was, it was a pleasant sight to us; not only as being the first land we had seen, but because it told us that we had passed the Cape,—were in the Atlantic,—and that, with twenty-four hours of this breeze, might bid defiance to the Southern Ocean. It told us, too, our latitude and longitude better than any observation; and the captain now knew where we were, as well as if we were off the end of Long wharf.
>In the general joy, Mr. N. said he should like to go ashore upon the island and examine a spot which probably no human being had ever set foot upon; but the captain intimated that he would see the island—specimens and all,—in—another place, before he would get out a boat or delay the ship one moment for him.
>We left the land gradually astern; and at sundown had the Atlantic Ocean clear before us.