Sir Roderick Impey Murchison (1792-1871), Scottish geologist and geographer. Following his military career, which ended after the Peninsular War in Spain & Portugal, he became a member of the London Geological Society. In 1855 he become president. Murchison published the Silurian System in 1839, which was the first stratigraphic system defined by fossil content rather than lithology (rock features). Following geological tours of Scotland, Russia and Germany, he established the Devonian and Permian systems geological dating. Leaving geology, he become head of the Royal Geographical Society, where he encouraged British exploration around the world.