David Rittenhouse, an American mathematician, born at Germantown, Pa. (near which his great-grandfather, William Rittinghuysen, a Hollander, had established about 1690 the first paper mill in America), April 8, 1732, died in Philadelphia, June 26, 1796. During his youth he came into possession of the tools and mathematical books of a deceased uncle, made clocks without any instruction, and followed the occupation of clock making. He was commissioned by the proprietary government in 1763 to determine the initial portion of the boundary line since known as Mason and Dixon's; and although his instruments were all of his own construction, the official surveyors adopted his measurements. He was subsequently employed in determining the boundaries between New York, New Jersey, and Pennsylvania, and other states. He calculated the transits of Venus of June 3, 1769, and Dec. 8, 1874, and made a successful observation of the former in his observatory at Norriton. In 1770 he removed to Philadelphia, and in 1775 was elected to the provincial legislature.

He was a member of the convention called to form a state constitution, state treasurer from 1776 to 1789, and director of the United States mint from 1792 to 1795. In 1791 he succeeded Franklin as president of the American philosophical society, to whose "Transactions" he had contributed many papers, and in 1795 he was chosen a fellow of the royal society of London. - See his life by William Barton (8vo, Philadelphia, 1813), and by Prof. James Ren-wick in Sparks's "American Biography".