HUYGENS (Christian)

, a very eminent astronomer and mathematician, was born at the Hague in Holland, in 1629, being the son of Constantine Huygens, lord of Zuylichem, who had served three successive princes of Orange in the quality of secretary. He spent his whole life in cultivating the mathematics; and not in the speculative way only, but also in making them subservient to the uses of life. From his infancy he discovered an extraordinary fondness for the mathematics; in a short time made a great progress in them; and perfected himself in those studies under professor Schooten, at Leyden. In 1649 he went to Holstein and Denmark, in the retinue of Henry count of Nassau; and was extremely desirous of going to Sweden, to visit Des Cartes who was then in that country with the queen Christina, but the count's short stay in Denmark would not permit him.—In 1651 he gave the world a specimen of his genius for mathematics, in a treatise intitled, Theoremata de Quadratura Hyperboles, Ellipsis, & Circuli, ex dato Portionum Gravitatis Centro; in which he clearly shewed what might be expected from him afterwards.——In 1655 he travelled into France, and took the degree of LL.D. at Angers.— In 1658 he published his Horologium Oscillatorium, sive de Motu Pendulorum, &c, at the Hague. He had ex-| hibited in a former work, intitled, Brevis Institutio de Usu Horologiorum ad inveniendas Longitudines, a model of a new invented pendulum; but as some persons, envious of his reputation, were labouring to deprive him of the honour of the invention, he wrote this book to explain the construction of it; and to shew that it was very different from the pendulum of astronomers invented by Galileo.—In 1659 he published his Systema Saturninum, &c; in which he first of any one explained the ring of Saturn, and discovered also one of the satellites belonging to that planet, which had hitherto escaped the eyes of astronomers: new discoveries, made with glasses of his own forming, which gained him a high rank among the astronomers of his time.

In 1660, he took a second journey into France, and the year after passed over into England, where he communicated his art of polishing glasses for telescopes, and was made Fellow of the Royal Society. About this time the air-pump was invented, which received considerable improvements from him. This year also he discovered the laws of the collision of elastic bodies; as did also about this time Wallis and Wren, with whom he had a dispute about the honour of this discovery. Upon his return to France, in 1663, the minister Colbert, being informed of his great merit, settled a considerable pension upon him, to engage him to fix at Paris; to which Mr. Huygens consented, and staid there from the year 1666 to 1681, where he was admitted a member of the Academy of Sciences. All this time he spent in mathematical pursuits, wrote several books, which were published from time to time, and invented and perfected several useful instruments and machines: particularly he had a d<*>spute, about the year 1668, with Mr. James Gregory, concerning the Quadrature of the Circle and Hyperbola of the latter, then just published, in which Huygens it seems had the better side of the question. But continual application gradually impaired his health; and though he had visited his native country twice, viz, in 1670 and 1675, for the recovery of it, he was now obliged to betake himself to it altogether. Accordingly he left Paris in 1681, and retired to his own country, where he spent the remainder of his life in the same pursuits and employments. He died at the Hague, June 8, 1695, in the 67th year of his age, while his Cosmotheoros, or treatise concerning a plurality of worlds, was printing; so that this work did not appear till 1698.

Mr. Huygens loved a quiet and studious manner of life, and frequently retired into the country to avoid interruption, but did not contract that moroseness which is so commonly the effect of solitude and retirement. He was one of the purest and most ingenious mathematicians of his age, and indeed of any other; and made many valuable discoveries. He was the first who discovered Saturn's ring, and a third satellite of that planet, as mentioned above. He invented the means of rendering clocks exact, by applying the pendulum, and of rendering all its vibrations equal, by the cycloid. He brought telescopes to perfection, and made many other useful discoveries.

He was the author of many excellent works. The principal of these are now contained in two collections, of 2 volumes each, printed in 4to, under the care of professor Gravesande. The first was at Leyden in 1682, under the title of Opera Varia; and the second at Amsterdam, in 1728, entitled Opera Reliqua.