Born Oct. 15, 1829, in Goshen, Conn.; died Nov. 22, 1907, in Annapolis, Md. American astronomer. Member of the National Academy of Sciences (1875).

From 1857 to 1862, Hall worked as an assistant at the Harvard University Observatory, and from 1862 to 1891 he was an astronomer at the U.S. Naval Observatory in Washington, D.C. He was a member of the faculty at Harvard University from 1896 to 1901. Hall is known for his observations of asteroids, binary stars, and the planets and their satellites. In 1876 he determined Saturn’s period of rotation, and in 1877 he discovered the satellites of Mars. Hall worked to develop a theory of the motions of the planets and their satellites.