Page:Appletons' Cyclopædia of American Biography (1900, volume 5).djvu/289

miniature when he was eight years old, and at seventeen he made a wooden clod;, and later one in metal. In 1751 he persuaded his father to ad- vance money with which he purchased in Phila- delphia an 'outfit of tools, and then established himself in Norriton as a clock- and mathematical- instrument-maker. His days were spent in fol- Inwing his trade, and his "nights were given to' study, lie M lived abstruse mathematical and as- tnniiimicul problems, discovering for himself the method of fluxions, and for a long time believing that he was its originator. He mastered an English translation of Newton's " Principia," also devoting himself to the study of optics. In 1751 he became acquainted with Thomas Barton (q. t 1 .), who supplied him with books, from which he gained a knowledge of Latin and Greek. His clocks became celebrated for their accuracy : he obtained a local reputation lor astronomical knowledge, and through Mr. Bar- ton, who became his brother-in-law, he was intro- duced to men of learning. In 1763 he was called on to determine the initial and most difficult part of the boundary-line between Pennsylvania and Maryland, and this task was so well accomplished that he was offered extra compensation on its com- pletion. Although the instruments were of his own manufacture, when the official astronomers, Charles Mason and Jonathan Dixon, arrived in 1763, they accepted his observations without change. He was appointed in 1769, at the request of a commis- sion that was selected by New York and New Jer- sey, to settle the boundary-lines between these colo- nies. Meanwhile he continued his scientific re- searches, studied the variations in the oscillations of the pendulum that are caused by the expansion and contraction of the material from which it was made, and devised a satisfactory plan of compen- sation ; also about this time he made a thermome- ter on the principle of the expansion and contrac- tion of metals. Later he constructed an orrery on a new and more perfect plan than had ever before been attempted, which, when it was finished in 1770, was regarded by John Adams as " a most beautiful machine. ... It exhibits almost every motion in the astronomical world." Princeton purchased it for 300, and later Rittenhouse made a larger in- strument from the same model for the University of Pennsylvania, for which he received 400. In January, 1768, he was elected a member of the American philosophical society, and in June of that year he addressed the society on the transit of Ve- nus that occurred on 3 June, 1769, in consequence of which three committees were appointed by that body to make observations. One of these, under Rittenhouse, was stationed at his observatory in Norriton, and all of the preliminary arrangements were left to him. He set to work with great zeal ; Thomas Penn sent a reflector from Europe, and other apparatus was secured, all of which Ritten- house mounted. The observations, according to the testimony of the astronomer royal of England, were excellent, and, according to another authority, " the first approximately accurate results in the measurement of the spheres were given to the world, not by the schooled and salaried astronomers who watched from the magnificent royal observatories of Europe, but by unpaid amateurs and devotees to science in the youthful province of Pennsylva- nia." In 1769 he observed the transit of Mercury, and a year later he calculated the elements of the motion and the orbit of a comet. In 1770 he re- moved to Philadelphia, where he continued to en- fage in mechanical pursuits, and also for some years ad charge of the state-house clock. He continued his experiments, and in 1771 investigated the elec- trical properties of the gymnotus, or electric eel. In 1772 lie was engaged to survey and ascertain the IcvrN of the lands between the Suscjuehanna and Delaware rivers, and in 1773 he was chief of a com- misison to make the Schuylkill river navigable. He was commissioner from Pennsylvania in 1774 to determine the northwestern extremity of the boun- dary between New York and Pennsylvania. In March. 1775, the American philosophical society presented for the consideration of the Pennsylvania assembly a plan for the erection of an observatory under state control, with a view of tendering the appointment of director to Mr. Rittenhouse. The Revolutionary war prevented the carrying out of this project, and he was ordered " to prepare moulds for the casting of clock-weights, and send them to some iron-furnace, and order a sufficient num- ber to be immediately made for the purpose of ex- changing them with the inhabitants of this city for their leaden clock-weights." In October, 1775, he was appointed engineer to the committee of safety, and in that capacity he was called upon to arrange for casting cannon of iron and brass, to view a site for the erection of a Continental powder-mill, to conduct experiments for rifling cannon and musket- balls, to fix upon a method of fastening the chain for the protection of the river, to superintend the manufacture of saltpetre, and to locate a magazine for military stores on Wissahickon creek. He was appointed one of the committee of safety in April, 1776, its vice-president in August, and in Novem- ber the proclamations that were issued bore his name as presiding officer. In March, 1776, he was elected a member of the assembly from Phila- delphia, and later he became a member of the con- vention that met on 15 July, 1776. and drafted the first constitution for the state of Pennsylvania. He was one of the board of war for the state of Penn- sylvania, and later one of the council of safety, to whom the most absolute powers were temporarily granted. In January, 1777, he was elected first state treasurer under the new constitution, and he was unanimously elected to the same office for twelve years, until finally, in 1789, he declined to serve any longer. On several occasions he was ap- pointed to act on various boundary commissions, and in 1792 he was appointed first director of the mint, which place he filled for three years. From 177!) till 1782 he was professor of astronomy in the University of Pennsylvania, and also a trustee and vice-provost of the same institution. In 1772 he received the honorary degree of A. M. from Princeton, and in 1789 the same college conferred on him the degree of LL. D. He was elected a fellow of the American academy of arts and sciences in 1782, and in 1795 he was chosen an honorary fellow of the Royal society of London. In 1771 he was elected one of the secretaries of the American philosophical society, of which he became vice- president in 1786, and, on the death of Benjamin Franklin in 1790, he was chosen its president, which office he then held until his death. The early vol- umes of the transactions of that society were en- riched by his scientific contributions, about twenty in number; his most elaborate paper. "An Ora- tion on Astronomy" (Philadelphia, 1775), was de- livered on 24 Feb., 1775. Thomas Jefferson, who succeeded him as president of the Philosophical so- ciety, wrote : " We have supposed Mr. Rittenhouse second to no astronomer living ; that in genius he must be first, because he is self-taught." See " Life of David Rittenhouse," by James Renwick, in Sparks's "American Biography" (Boston, 1834), and " Memoirs of the Life of David Rittenhouse," by William Barton (Philadelphia, 1813).