It was on Jan. 11, 1671, that Newton was elected a member of the royal society, having become known to that body from his reflecting telescopes. At what period he restnned his calculations about gravitation, employing the more correct measure of the earth obtained by Picard in 1670, does net clearly appear; but it was in the year 1681 that it became known to Halley that he was in possession of the whole theory and its demonstration. It was on the urgent solicitation of Halley that he was induced to com mit to a systematic treatise these principles and their demonstrations. The principal results of 'his discoveries were set down iu a treatise called De Motu Corporum, and were afterwards more completely unfolded in the great work entitled Philosophia Naturals Principal, which was finally published about midsummer, 1687.
Shortly before the Pritteipia was given to the public, Newton had been called to take an active part in defending the rights of the university against the illegal encroachments of James II. The conspicuous part which he had taken on that occasion procured him a seat in the convention parliament, in which lie sat from Jan., 1689, to its dissolution in 1690. lu 1696 lie was appointed warden of the mint, and was afterwards promoted to the office of master of the mint in 1699, an office which he held till the end of his life. Ile again took a seat in parliament, in the year 1701, as the representative of his univer sity. Thus engaged in the public service, he had little time left for mere scientific stud ies—pursuits which he always held of secondary importance to the public duties in which he was engaged. In the interval of public duty, however, Newton showed that be still retained the scientific power by which his great discoveries had been made. This was shown in his solution of two celebrated problems proposed in June, 1696, by John Bernouilli, as a challenge to the mathematicians of Europe. A similar mathematical feat is recorded of hint so late as 1716 in solving a problem proposed by Leibnitz, for the purpose, as he expressed it, of feeling the pulse of the English analysts. When in parliament, Newton recommended the public encouragement of the invention of a method for determining the longitude—the first reward in consequence being gained by John Harrison for his chronometer. He was president of the royal society from 1703
till his death, a period of twenty-five years, each year re-elected. In this position, and enjoying the confidence of prince George of Denmark, he had much in his power towards the advancement of science; and one of his most important works during this time was the superintendence of the publication of Flamsteed's Greenwich Obseriettions a task, however, not accomplished without much controversy and some bitterness between himself and that astronomer. The controversy between Newton and Leibnitz, as to priority of discovery of the differential calculus, or the method of flexions, was raised rather through the partisanship of jealous friends titan through the anxiety of the philosophers themselves, who were, however, induced to enter into and carry on the dis pute with some degree of bitterness and mutual recrimination. The verdict of the impartial historian of science must be that the methods were invented quite indepen .
dently, and that, althount Newton was the first inventor, a greater debt is owing by later analysts to Leibnitz, on account of the superior facility and completeness of his method. The details of these controversies, with all other information of the life of this philosopher, will be found admirably collected in the life by sir D. Brewster, who writes with not only an intimate acquaintance with Newton's works, but in the possession of all the materials collected in the hands of his family. Newton died on Mar. 20, 1727, and his remains received a resting-place in Westminster abbey, where a monument was erected to his memory in 1731. magnificent full-length statue of the philosopher, executed by Tioubilliac, was erected in 1755 in the antechapel of Trinity college, Cam bridge. This work was assisted by a cast of the face taken after death, which is pre served in the university library at Cambridge. In 1699 Newton had been elected a foreign associate of the academy of sciences, and in 1703 lie received the honor of knighthood from queen Anne. Amon„ -the best editions pf Newton's-principal works are the quarto edition of the Optics (Loud. 1704), and the quarto edition of the Principle, published at Cambridge in 1713.