HAYDEN, Ferdinand Vandeveer, geologist, born in Westfield, Massachusetts, 7 September, 1829. He early settled in Ohio, and, after his graduation at Oberlin in 1850, received his medical degree at the Albany medical college in 1853. During the same year he explored the "Bad Lands" of Dakota for James Hall, state geologist of New York, and returned with a large and valuable collection of fossil vertebrates. In 1854 he again went west, spent two years in exploring the basin of the upper Missouri, and returned with a large number of fossils, part of which he deposited in the St. Louis academy of science, and the remainder in the Philadelphia academy of natural sciences. These collections attracted the attention of the authorities of the Smithsonian institution, and he was appointed geologist on the staff of Lieutenant Gouverneur K. Warren, of the topographical engineers, who was then making a reconnoissance of the northwest, after which, in May, 1859, he was appointed naturalist and surgeon to the expedition sent out for the exploration of the Yellowstone and Missouri rivers under Captain William F. Raynolds. He continued in this capacity until May, 1862, when he entered the United States army as assistant surgeon of volunteers, and was assigned to duty in the Satterlee hospital in Philadelphia, becoming full surgeon on 19 February, 1863, when he was sent to Beaufort, South Carolina, as chief medical officer. In February, 1864, he became assistant medical inspector of the Department of Washington, and in September, 1864, he was sent to Winchester, Virginia, as chief medical officer of the Army of the Shenandoah. This office he held until May, 1865, when he resigned and was given the brevet of lieutenant-colonel. He was appointed professor of mineralogy and geology in 1865 in the University of Pennsylvania, and held that chair until 1872, when the increased duties of the survey caused his resignation. During the summer of 1866 he again visited the valley of the upper Missouri for the Philadelphia academy of sciences, and gathered valuable vertebrate fossils. In 1867 congress provided for the geological survey of Nebraska. Dr. Hayden was directed to perform the work, and continued so occupied until 1 April, 1869, when it was organized under the title of the Geological survey of the territories of the United States. From 1869 till 1872 Dr. Hayden conducted a series of geological explorations in Dakota, Wyoming, Utah, and Colorado, the scope of investigation including, besides geology, the natural history, climatology, resources, and ethnology of the region. It was largely in consequence of his explorations and reports that congress was led to set apart the Yellowstone national park as a perpetual reservation. In 1873 geography was added, and the name of the organization then became the Geological and geographical survey of the territories. Dr. Hayden continued the direction of this survey until 1879, when the then existing national surveys were consolidated into the United States geological survey, and Dr. Hayden was made geologist-in-charge of the Montana division. He held this office until 31 December, 1886, when failing health led to his resignation. Dr. Hayden is a member of scientific societies both in the United States and in Europe, and in 1873 was elected to the National academy of sciences. In 1887 the degree of LL.D. was conferred on him by the University of Pennsylvania. He has written numerous scientific papers, and his government publications have been very large. The latter include annual reports of his work performed from 1867 till 1879; also a series of "Miscellaneous Publications" on special subjects written by authorities in the specialties of which they treat, and a series of quarto volumes entitled "Report of the United States Geological Survey of the Territories."