RITTENHOUSE David (1732-1796), astronomer, was born at Germantown, Pennsylvania, on April 8, 1732. First a watchmaker, he afterwards became treasurer of Pennsylvania and (from 1792) master of the United States mint; he was largely occupied in settling the boundaries of several of the States. As an astronomer, Rittenhouse’s principal merit is that he introduced the use of spider lines in the focus of a transit instrument. His priority with regard to this useful invention was acknowledged by Troughton, who brought spider lines into universal use in astronomical instruments (see Von Zach’s Monatliche Cor-respon/lenz, vol. ii. p. 215), but Felice Fontana (1730-1805) had already anticipated the invention, though no doubt this fact was unknown to Rittenhouse. He died on 26th June 1796.