Paul H Barrett 
The Works of Charles Darwin: v. 9: Geological Observations on South America (1846) (with the Critical Introduction by J.W. Judd, 1890) [PDF ebook] 

The ninth volume in a 29-volume set which contain all Charles Darwin”s published works. Darwin was one of the most influential figures of the 19th century. His work remains a central subject of study in the history of ideas, the history of science, zoology, botany, geology and evolution.