The collection of letters from the British naturalist Alfred Russel Wallace (1823 – 1913) can be explored in the website of the Natural History Museum of London. This collection includes correspondence between Wallace and Charles Darwin, Thomas Henry Huxley and Joseph Dalton Hooker, to name a few.
The letters also show observations made by Wallace when he was doing fieldwork in the Malay Archipelago. Besides that, it is also possible to find discussions on a variety of subjects, such as glaciology, anthropology, epidemiology, astrobiology, socialism, land reform and spiritualism.
Source: The Alfred Russel Wallace Correspondence ProjectVisit the website Waalace Letters OnlineVisit the Alfred Russel Wallace Project