TURNBULL, William, engineer, born in Philadelphia, Pennsylvania, 9 October, 1800; died in Wilmington, North Carolina, 9 December, 1857. He was graduated at the United States military academy in 1819, and entered the army as 2d lieutenant in the artillery. After serving in garrison at Fort McHenry for a year he was on topographical duty until 1832, being made in 1831 assistant topographical engineer, with the brevet of captain. From 1832 till 1843 he was superintending topographical engineer of the construction of the Potomac aqueduct. This work, one of the earliest of the important undertakings of American engineers, gave Colonel Turnbull a high rank among his professional associates. The piers of the aqueduct were founded by coffer-dams on rock, sometimes covered by twenty feet of mud, and nearly forty feet below the water surface. He was made major, 7 July, 1838, and had charge of the repairs of the Potomac (long) bridge in 1841-'3. Subsequently he had charge of Lake Ontario harbor improvement, the extension of Buffalo harbor, and inspection of harbor improvements on Lake Champlain, Lake Ontario, and Lake Erie. In the war with Mexico he was topographical engineer of the army under General Winfield Scott, and was engaged in the siege of Vera Cruz, the castles of Cerro Gordo, Pedregal, and Churubusco, and the operations that ended with the capture of the city of Mexico. His services gained for him the brevets of lieutenant-colonel and colonel. During 1848-'9 he had charge of the construction of the New Orleans custom-house, and he was assistant in the topographical bureau at Washington, D. C., in 1850-'2 and 1853-'4, where he examined into the practicability of bridging Susquehanna river at Havre de Grace, and the expediency of an additional canal around the Falls of Ohio. He was light-house engineer for Oswego harbor, New York, in 1853-'5, in charge of harbor improvements of Lake Champlain, Lake Ontario, and the eastern part of Lake Erie in 1853-'6, and of the improvement of Cape Fear river, North Carolina, in 1856-'7. The illustration shown above represents the Potomac aqueduct as designed by him. Among his various government reports that were published was one "On the Survey and Construction of the Potomac Aqueduct," with twenty-one plates (Washington, 1838).--His son, Charles Nesbit, engineer, born in Washington, D. C., 14 August, 1832; died in Boston, Massachusetts, 2 December, 1874, was graduated at the United States military academy in 1854, and made 2d lieutenant of topographical engineers. He was on the survey of the boundary-line between the United States and Mexico in 1854-'6, on that of the northern lakes in 1856-'9, and at the United States military academy as assistant professor of mathematics in 1859-'60. During the civil war he served at first on the staff of General Benjamin F. Butler and in the Department of the Gulf, after which, in 1863-'4, he was with the Army of the Potomac. He received his promotion as captain of topographical engineers, 14 July, 1862, and was transferred to the corps of engineers on 3 March, 1863. In June, 1864, he was chief engineer of the cavalry corps, during General Philip H. Sheridan's raid, and later chief engineer of the 8th army corps. He received the brevets of major, lieutenant-colonel, and colonel for his services, and after the war served on the repairs of Fort Hamilton. Colonel Turnbull resigned on 31 December. 1865, and engaged in the commission business in Boston, Massachusetts, where he continued until his death.