Huygens, CHRISTIAN

Huygens, CHRISTIAN, one of the great philosophers of the 17th century, was born at the Hague, April 14, 1629, and was the second son of Constantine Huygens, poet, diplomatist, and secretary to the Prince of Orange, who was knighted by James I. of England in 1622. Huygens studied at Leyden and Breda. His first work, Theorematum de Quadratura Hyperbolicæ, Ellipsis, et Circuli (1651), is an example of that powerful geometrical talent which lay at the foundation of all his scientific achievements. Soon after this he constructed the pendulum-clock, following out the idea first suggested by Galileo (see HOROLOGY). A complete description of Huygens' instrument is contained in his great work, Horologium Oscillatorum (1673). This work contains expositions of many of the cases of constrained motion, especially those applicable to the construction of timekeepers. Huygens also developed and gave precision to the investigations of Galileo upon accelerated motion under the action of gravity; and there is no doubt that to the clearness of his demonstrations his great successor, Newton, in preparing his magnificent development of the principle of accelerating force, was largely indebted. Newton was a student and admirer of his works, and assigns to him, along with Sir C. Wren and Wallis, the distinguished epithet of hujus ætatis geometerum facile principes. By means of an improved telescope of his own construction, Huygens in 1655 discovered the ring of Saturn and the fourth satellite of that planet. In 1659 he published an account of these discoveries in a work entitled Systema Saturnium. In the end of this work the Micrometer (q.v.) is described. In 1660 Huygens visited England, where he was admitted a member of the Royal Society. He discovered the laws of collision of elastic bodies about the same time as Wallis and Wren, and also made a material improvement in the air-pump. But his most important discoveries are in the department of optics; he it was who first propounded and developed what is now known as the undulatory theory of Light (q.v.), and he is the discoverer of Polarisation (q.v.). The 'principle of Huygens' is a part of the wave-theory. In 1666 Huygens received an invitation to settle in France, with the promise of a pension from Colbert, then all-powerful in that country. At Paris he remained till 1681, a member of the Royal Academy of Sciences; but alarmed at the danger which seemed impending over the Protestants, he returned to his own country, and died at the Hague, 8th July 1693. His Œuvres Complètes have been issued since 1888 by the Amsterdam Academy of Sciences.