Sir Roderick Impey Murchison, (1792-1871) was a Scottish geologist who first established the geologic sequence of Early Paleozoic strata. Murchison joined the Geological Society of London in 1825 and in the following five years explored Scotland, France, and the Alps an collaborated alternately with the British geologists Adam Sedgwick and Charles Lyell. In 1831 he was elected president of the Geological Society and also began his field studies of the Early Paleozoic rocks in South Wales. He published his findings in 1839 in the monumental work The Silurian System. With the establishment of the Silurian System, Murchison and Sedgwick then founded the Devonian System, based on their research of the geology of southwestern England and the Rhineland. After studying the geology of Russia he collaborated with other to write and publish in 1845 The Geology of Russia in Europe and the Ural Mountains. His work in Russia also led in 1841 to his proposed establishment of the Permian System. By this time his friendship with Adam Sedgwick was at an end. Sedgwick's stratigraphy claimed rock for his Cambrian System. Murchison claimed the same strata for his Silurian System. The feud lasted the rest of their lives and was only settled in 1879 when the geologist Charles Lapworth assigned the older rocks to the Cambrian, the newer rocks to theSilurian and inserted a new period in between which was the Ordovician. In 1854 Murchison published his work Siluria. In it he presented the main features and arguments for his original work SilurianSystem along with new information based on his most recent findings. The work was highly popular and went through five editions with the last published in1872. He also argued against his Silurian System being split into Cambrian, Ordovician and Silurian.