The improvement of telescopes was prosecuted by Christiaan Huygens from 1655, and promptly led to his discoveries of the sixth Saturnian moon, of the true shape of the Saturnian appendages, and of the multiple character of Huygens.
Now the direction and phase of the light are those of the ray which reaches the eye; and by Fermat's principle, established by Huygens for undulatory motion, the path of a ray is that track along which the disturbance travels in least time, in the restricted sense that any alteration of any short reach of the path will increase the time.
Uylenbroek, Oratio de fratribus Christiano atque Constantino Hugenio (Groningen, 1838); P. Harting, Christiaan Huygens in zijn Leven en Werken geschetzt (Groningen, 1868); J.
Although Robert Hooke in 1668 and Ignace Pardies in 1672 had adopted a vibratory hypothesis of light, the conception was a mere floating possibility until Huygens provided it with a sure foundation.
Among other writers, Leibnitz and Huygens give testimony which is the more valuable as being critical.
It was as an optician that he was first brought into connexion with Huygens and Leibnitz; and an optical Treatise on the .Rainbow, written by him and long supposed to be lost, was discovered and reprinted by Dr Van Vloten in 1862.
He continued his scientific correspondence with unbroken interest and undiminished logical acumen; he thought out the application of the pendulum to the regulation of clockwork, which Huygens successfully realized fifteen years later; and he was engaged in dictating to his disciples, Viviani and Torricelli, his latest ideas on the theory of impact when he was seized with the slow fever which in two months brought him to the grave.
He also received the De Morgan medal from the London Mathematical Society, and the Huygens medal from Leiden.
The theorems on the composition of forces in circular motion with which it concluded formed the true prelude to Newton's Principia, and would alone suffice to establish the claim of Huygens to the highest rank among mechanical inventors.
CHRISTIAAN HUYGENS (1629-1695), Dutch mathematician, mechanician, astronomer and physicist, was born at the Hague on the 14th of April 1629.