A great travelogue recounting a sea voyage from Britain to Porto Velho on the Amazon river system in 1909 - 1910. I found it through James Mustich’s 1,000 Books to Read Before You Die. It was published in 1912 and is free as an e-book. As much as I liked it, be warned that I sometimes struggled with the author’s florid Edwardian prose. He can wax poetical when describing the Amazon, but also when discussing not much at all. His sentences may run on and sometimes run backward. There are scattered words that are no longer used much, if they were then, and a few are not in the dictionaries I have access to. You may need to bear with him until he is well at sea. Here is a suggestive example:
From our narrow and weltering security, where the wind searched through us like the judgment eye, I know, looking out upon the wilderness in turmoil where was no help, and no witness of our undoing, where the gleams were fleeting as though the very day were riven and tumbling, that I saw the filmy shapes of those things which darken the minds of primitives.
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Watch out for the story within the story that reads like a miniature version of Heart of Darkness.