Stephen Harriman Long, an American engineer, born in Hopkinton, N. II., Dec. 30, 1784, died in Alton, 111., Sept. 4, 1864. He graduated at Dartmouth college in 1809, in 1814 entered the corps of engineers of the United States army, and in 1815 became assistant professor of mathematics at West Point. In April, 1816, he was transferred to the topographical engineers. From 1818 to 1823 he had charge of explorations between the Mississippi and the Rocky mountains, and of the sources of the Mississippi in 1823-'4, and in 1826 was made brevet lieutenant colonel of topographical engineers. He was engaged in surveying the Baltimore and Ohio railroad from 1827 to 1830, and from 1837 to 1840 was engineer-in-chief of the Western and Atlantic railroad in Georgia, in which capacity he introduced a system of curves in the location of roads, and a new species of truss bridges, which has been generally adopted in the United States. He was made major in 1838, colonel March 3, 1803, and retired June 1, 1863. An account of his first expedition to the Rocky mountains (of which one of the highest summits was named from him Long's peak) in 1819-'20, from the notes of Major Long and others, by Edwin James, was published in 1823; and in 1824 appeared " Long's Expedition to the Source of St. Peter's River, Lake of the Woods," etc, by W. H. Keating (2 vols., Philadelphia). His "Railroad Manual" (1829) was the first original treatise of the kind in this country.