OLMSTED, Denison (1791-1859), man of science, was bom at East Hartford, Connecticut, U.S.A., on 18th June 1791, and became a student of Yale, where he graduated in 1813, and acted as college tutor from 1815 to 1817. In the latter year he was appointed to the chair of chemistry, mineralogy, and geology in the university of North Carolina. This chair he exchanged for that of mathematics and physics at Yale in 1825; in 1836, when this professorship was divided, he retained that of astronomy and natural philosophy. He died at New Haven, Connecticut, on 13th May 1859.

His first publication (1824-25) was the Report of his geological survey of the State of North Carolina. It was followed by various text-books on natural philosophy and astronomy, but he is chiefly known to the scientific world for his observations on hail (1830), on meteors, and on the aurora borealis. For his conclusions on the last-named subject see vol. viii. of the Smithsonian Contributions.