MARCOU, Jules (mar-koe), geologist, born in Salins, Jura, France. 20 April, 1824. He studied at the college of Besangon, and that, of St. Louis in Paris, after which failing health led to his making excursions into Switzerland, where he acquired a fondness for natural science. In 1845 he became associated with , Jules Thurmann in his work on the geology of the Jura, mountains, and while engaged in this undertaking met Louis Agassiz. He was appointed assistant in the mineralogical department of the Sorbonne in 1846, and also classified its collection of fossils. In 1847 he was made travelling geologist for the Jardin des plantes, and was sent to study the United States and the English possessions in North America. He accompanied Louis Agassiz to Lake Superior, visited the copper-mines of Keweenaw point, Lake Huron, and Niagara, returning to Cambridge after six months' exploration and sending to Paris valuable collections of minerals. In January, 1849, he directed his attention to the geology of New Jersey, Pennsylvania, and Virginia. Later he crossed the Alleghany mountains, visiting the Mammoth cave and other localities, and then traversed Canada and the adjacent provinces. He returned to Europe in 1850, but soon came back to the United States, and was occupied with the preparation of his "Geological Map of the United States and British Provinces of North America" (2 vols., Boston, 1853). In 1853 he entered the United States service, was the first geologist that crossed the United States, being attached to the Pacific railroad exploration of the 35th parallel, and made a section from the Mississippi river to the Pacific ocean. Failing health compelled his return to Europe, and in 1855-'9 he was professor of geology in the Polytechnic school of Zurich. In 1861 he returned to the United States, and was associated with Louis Agassiz in the foundation of the Museum of comparative zoology, having charge of the paleontological division in 1860-'4. Subsequently he devoted himself to scientific research until 1875, when he again entered the National service in his professional capacity. He is a member of scientific societies, and was decorated with the cross of the Legion of honor in 1867. Since the death of Ebenezer Emmons (q. v.), Professor Marcou has been the strongest supporter of the Taconic system of New York, publishing nearly a dozen important papers on that system in Vermont and Canada. In addition to numerous scientific memoirs, he has published " Recherches geologiques sur la Jura Salinois" (Paris, 1848)'" Geology of North America" (Zurich, 1858)"Lettres sur les roches du Jura et leur distribution geographique dans les deux hemispheres" (Paris, 1860) ; "Geological Map of the World" (Winterthur, 1861; 2d ed., Zurich, 1875)" "De la science en France" (Paris, 1869)" and "A Catalogue of Geological Maps of America" (Washington, 1884) ; and "The Taconic System and its Position in Stratigraphic Geology" (Cambridge, 1885). In geography he has explained the origin of the name American in "Origin of the Name America" (Boston, 1875, and Paris, 1887), and "First Discoveries of California, and the Origin of its Name" (Washington, 1878).