OLMSTED, Denison, physicist, born in East Hartford, Connecticut, 18 June, 1791; died in New Haven, Connecticut, 13 May, 1859. He was graduated at Yale in 1813, and was at once given charge of the Union school in New London. In 1815 he returned to Yale as tutor, and began the study of theology, with a view to the ministry, but in 1817 he was called to the chair of chemistry, mineralogy, and geology in the University of North Carolina. Here he proposed and executed the first state geological survey that was ever attempted in the United States, publishing reports of his work in 1824 and 1825. Although the state authorized the execution of the survey, Professor Olmsted received no compensation for his services. He was appointed in 1825 professor of mathematics and natural philosophy in Yale, which chair he retained until 1836, when it was divided at his request, and the department of mathematics assigned to Anthony D. Stanley. In addition to the duties of his professorship, fie devoted much time to the study of the various branches of physical science. He published an elaborate theory of hail-stones in 1830, which caused much discussion, but finally received the general approbation of meteorologists. The shower of shooting-stars that fell in November, 1833, attracted his attention, and he studied their history, and behavior until he was able satisfactorily to demonstrate their cosmical origin. Professor Olmsted, and his associate, Elias Loomis (q. v.), were in 1835 the first American investigators to observe the Halley comet. For several years he carried on a series of observations of the aurora borealis, the results of which were published in the "Smithsonian Contributions to Knowledge" (vol. viii., Washington, 1856). Professor Olmsted possessed considerable mechanical talent, which he used in promoting and perfecting the inventions of others, but while he himself frequently invented articles of convenience and comfort, such as the Olmsted stove, he seldom secured his rights by patents. He was a member of scientific societies, and his more technical papers may be found in their transactions Professor Olmsted likewise was a large contributor to the reviews and to other periodical literature, especially in the direction of biography. He published "Life and Writings of Ebenezer Porter Mason" (New York 1842). He was also the author of text-books, of which the entire number of copies that were sold exceeded 200,000. They include " Student's Commonplace Book" (New Haven, 1828) ; "Introduction to Natural Philosophy" (2 vols., New York, 1831); "Compendium of Natural Philosophy" (1832)" "Introduction to Astronomy", (1839) ; "Compendium of Astronomy (1841) ; "Letters on Astronomy, addressed to a Lady" (1841); and " Rudiments of Natural Philosophy and Astronomy" (Cincinnati, 1844).--His son, Francis Allyn, physician, born in Chapel Hill, North Carolina, 14 July, 1819: died in New Haven, Connecticut, 19 July, 1844, was graduated at Yale in 1839. He made a sea voyage to the Sandwich islands for his health, and on his return was graduated at the medical department of Yale in 1844. He published "Incidents of a Whaling Voyage" (New York, 1841).--Another son, Alexander Fisher, chemist, born in Chapel Hill, North Carolina, 20 December, 1822 ; died in New Haven, Connecticut, 5 May, 1853, was graduated at Yale in 1844, and was called to fill the chair of chemistry in the University of North Carolina. He contributed scientific papers to the " Proceedings of the American Association for the Advancement of Science," of which society he was a member, and published "Elements of Chemistry" (New Haven, 1851).