http://www.npg.org.uk/collections/search/portrait/mw40351/Adam-Sedgwick?
Adam Sedgwick by Samuel Cousins, after Thomas Phillips mezzotint, published 1833, NPG D5929Adam Sedgwick by Samuel Cousins, after Thomas Phillips mezzotint, published 1833, NPG D5929
© National Portrait Gallery, London
Darwin's work on species shows many marks of his geological training. While he was attached to the Beagle from 1831 to 1836, Darwin actually spent about two-thirds of his time ashore, where geology was his single most frequent pursuit. After his return, he published three books on geology and developed a major theory of crustal uplift and subsidence which became the basis of an innovative explanation for the origin of coral reefs. Geology provided the long time span needed for a slowly acting process like natural selection to work, and tools for the reconstruction of processes operating in the distant past. In the last book published during his life, Darwin returned to geological studies by studying the action of worms, demonstrating the profound impact that these seemingly insignificant creatures had in the economy of nature.