Journal of Researches Into the Natural History and Geology of the Countries Visited During the Voyage Round the World of H.M.S. 'Beagle' Under the Command of Captain Fitz Roy, R. N.

Beagle sailed from Plymouth Sound on 27 December 1831 under the command of Captain Robert FitzRoy. While the expedition was originally planned to last two years, it lasted almost five—Beagle did not return until 2 October 1836. Darwin spent most of this time exploring on land (three years and three months on land; 18 months at sea). His Journal and Remarks is both a vivid travel memoir as a detailed scientific field journal covering biology, geology, and anthropology that demonstrates Darwin's keen powers of observation, written at a time when Western Europeans were exploring and charting the whole world. Although Darwin revisited some areas during the expedition, for clarity the chapters of the book are ordered by reference to places and locations rather than by date. Darwin's notes made during the voyage include comments hinting at his changing views on the fixity of species. On his return, he wrote the book based on these notes, at a time when he was first developing his theories of evolution through common descent and natural selection. The book includes some suggestions of his ideas, particularly in the second edition of 1845.