HALL, Asaph, astronomer, born in Goshen, Connecticut, 15 October, 1829. He was educated in a common school, and then worked on a farm till he was sixteen years old, after which he followed the trade of a carpenter. In 1853 he began the study of geometry and algebra in Norfolk academy, and afterward went to Wisconsin, where he taught school for several years. He then studied at the University of Michigan for a single term, and after teaching for a year at Shalersville, Ohio, entered the observatory of Harvard college as a student. From 1857 till 1862 he was assistant in the observatory, and in August of the latter year was appointed aide in the United States naval observatory in Washington. In May, 1863, he was made professor of mathematics, with the relative rank of captain. He has been connected with all the important astronomical expeditions sent out under the auspices of the United States government, including those sent to observe solar eclipses from the Bering sea in 1869, and in Sicily, in 1870. During the transit of Venus in 1874 he had charge of the American party at Vladisvostok, in Siberia, and at the later transit in 1882 was chief astronomer of the party stationed in San Antonio, Texas. Professor Hall has won great distinction by his discovery of the moons of Mars. On the night of 11 August, 1877, he noticed a small star near the disk of Mars, which, from subsequent examination, he was persuaded was a satellite of that planet. A week later he discovered a second satellite interior to the first, and of somewhat superior brightness. These discoveries were at once communicated to Joseph Henry, secretary of the Smithsonian institution, by whom they were announced to the principal astronomers both in Europe and America. Exact calculations were made of their orbits, and Professor Hall gave to them the names of Deimos and Phobos (Terror and Fear), from the passage in Homer's "Iliad," where these two divinities are mentioned as the attendants of the god of war. His subsequent work has included important observations of double stars in 1880, and determinations of the orbits of the satellites of Saturn. In 1879 he was awarded the gold medal of the Royal astronomical society of London for his discoveries, and received the degrees of Ph.D. from Hamilton in 1878, and LL. D. from Yale in 1879, and from Harvard in 1886. Professor Hall is a member of numerous scientific societies, both in the United States and Europe, and was chosen vice president of the American association for the advancement of science in 1880. In 1875 he was elected a member of the National academy of sciences, and in 1883 was appointed to the office of home secretary in that body. His publications have been confined to his specialty, and have appeared in astronomical journals on both continents, and also in the annual volumes of the United States naval observatory.