Murchison Sir Roderick Impey, a British geologist, born at Tarradale, Ross-shire, Scotland, Feb. 19, 1792, died in London, Oct. 22, 1871. He obtained a commission in the army in 1807, served during a portion of the peninsular war, and was employed on the staff of his uncle Sir A. Mackenzie in Sicily. He retired with the rank of captain of dragoons in 1815, married a daughter of Gen. Hugonin, and through her influence and the advice of Humphry Davy devoted himself to natural science. In 1825 he read a paper before the geological society "On the Geological Formation of the Northwest Extremity of Sussex, and the adjoining parts of Hampshire and Surrey." In 1827 he explored the highlands of Scotland, and in 1828 accompanied Lyell in a tour through France, studying the volcanic regions of Auvergne and the formation of valleys. He next undertook, with Prof. Adam Sedgwick, a systematic examination of the lower fossiliferous rocks of England and Wales. He partially remodelled the classification of the palaeozoic strata, and in 1832 first applied the term Silurian to a series of rocks intermediate between the Cambrian and Devonian formations.

Murchison recognized two main divisions as constituting the Silurian system, an upper and a lower, the latter of which he believed to lie imposed upon the upper Cambrian of Sedgwick. Subsequent researches have shown that the geological sections of Murchison, upon which his system was based, were in great part erroneous, and that his lower Silurian was identical with the upper Cambrian. This discovery gave rise to a long and acrimonious controversy between Sedgwick and Murchison and his partisans; but later researches, by comparing the justice of Sedgwick's views and the correctness of his determinations, are again bringing his nomenclature into use. (See Geology, and Sedgwick, Adam.) In 1839 appeared "The Silurian System," a revised edition of which was published in 1854 under the name of "Siluria." By invitation of the emperor Nicholas, Murchison, accompanied by De Verneuil and Keyserling, undertook a geological survey of Russia; and between 1840 and 1844 he explored the southern provinces of the empire, and a large portion of the Ural mountains, besides sections of Germany, Poland, Sweden, and Norway. He now conceived the idea of uniting the upper series of the palaeozoic rocks, consisting mainly of the lower new red sandstones and the subjacent magne-sian limestones, into a single group, for which he proposed the name Permian, from the prevalence of this formation in the ancient district of Perm. The results of the Russian expedition were published in a treatise " On the Geological Structure of the Northern and Central Regions of Russia in Europe " (London, 1841), and in " Geology of Russia in Europe and the Ural Mountains" (1845). In 1856 he published a geological map of Europe, and in 1861, conjointly with Geikie, one of Scotland. He was created grand cross of the Russian order of St. Stanislas in 1845, knighted in 1846, and made a baronet in 1866. In 1846 he was president of the British association.

On the death of Sir Henry T. De la Beche in 1855, he became director of the British geological survey, a post which he resigned shortly before his death. Murchison was one of the founders of the royal geographical society in 1830, was elected its president in 1843, was several times reelected, and held the office from 1862 until his death. It was chiefly through his influence that Dr. Livingstone was enabled to prosecute his researches in South Africa. He received the degrees of D. C. L. and LL. D. from the universities of England, and was an associate of nearly all scientific institutions. He opposed the evolution theory of Darwin, stanchly adhering to the doctrine of immutability. - See "Memoirs of Sir Roderick I. Murchison," by Archibald Geikie (2 vols., London, 1874).