384 



H U Y G E N S. 



uuygeos. causis mirandorutn Salitrrii phenomenon, et comitt: cjus 



""""if"" Plaiicla HOVO, -which contains the various important 



di.-covcrii's relative to the planet Saturn, of which we 



have already given a full account. .See ASTIIOXOMY, 



vol. ii. p. 598, 617, (US. 



In the year 1660, Huygens travelled into France ; 

 and in the following year he came to England, where 

 he made known his method of grinding the lenses of te- 

 JcM-opes. In the year 1663, he paid a second visit to 

 tills country, and was one of the hundred individuals 

 who were declared members of the Royal Society, at a 

 meeting of the council held on the 20th May 1663. 

 At this time the Royal Society had requested its mem- 

 bers to apply themselves to the consideration of the 

 laws of motion, and Huygens resolved several of 

 the cases which were proposed to him. On the 15th 

 November 1668, Dr Wullis communicated to the So- 

 ciety lu's principle of the collision of bodies. Doctor, 

 afterwards Sir Christopher, Wren made a similar com- 

 munication on the 17th of December; and on the 5th 

 January 1669, Huygens wrote a letter to Mr Ol- 

 denburgh, containing his first four rules, with their de- 

 monstration, concerning the motion of bodies after 

 impact. The method of Wallis was the most direct, 

 but related only to bodies absolutely hard. Wren's 

 method was founded on the same principle, but related 

 only to elastic bodies; and the method of Huygens 

 was the very same as that of Wren. 



Huygens had now acquired such a reputation, that, 

 in the year 1653, he was invited by Colbert to set- 

 tle in France. lie accepted of the honourable and ad- 

 vantageous conditions which were offered to him, and 

 took up his residence in Paris in 1666, when he was 

 admitted into the Academy of Sciences. In 1668, 

 he published, in the Journal des Sgavans, and also in 

 the Memoirs of the Academy, a paper entitled Ex- 

 amen du livre intitule Vcra Circuit el Hyperboles qiia- 

 dralura a Jacobo Gregorio, which led to the dispute 

 of which we have already given some account in our 

 life of GREGORY. In the year 1673, he published 

 his great work, entitled Horologium oscillatorium ; sive 

 de moiti pendulorum ad horolngia aplalo demonstrationes 

 geometrical, in which lie published his great discovery 

 of applying pendulums to clocks, and rendering all their 

 vibrations isochronous, by causing them to vibrate be- 

 tween cycloidal cheeks. This discovery was made 

 ahout the year 1656; and about the middle of 1657, 

 he presented to the States of Holland a clock construct- 

 ed on this new principle. In our article HOROLOGY, * 

 we have given a description and a drawing of this ma- 

 chine. The contrivance of cycloidal cheeks, however, 

 though exceedingly beautiful in theory, was found in 

 practice to be of no advantage. 



About this time our author invented the spiral 

 spring for regulating the balances of watches, without 

 knowing what had been done by Dr Hooke ; and he 

 applied to the French government for the exclusive 

 privilege of employing it. The Abbe Hautefeuille 

 had, however, conceived the first idea of this invention, 

 and communicated to the Academy of Sciences, in l674>, 

 the secret of regulating the balances of watches " by a 

 small straight spring made of steel." He therefore dis- 

 puted Huygens' right to the exclusive privilege, and 

 the affair was accommodated in consequence of Huy- 

 gens renouncing his claim. The observations of Mon- 

 tucla on this subject are certainly unjust towards the 



Abbe Hautefeuille, when he characterises his invention Hinder.*. 

 as rude and clumsy, and claims all the merit for Huy- s "-"f~~"' 

 gens. The idea of regulating the balance by a spring 

 was certainly the principal part of the invention, which 

 is unquestionably due to the Abbo Hautefeuille; while 

 Huygens is entitled to the credit of having perfected 

 the invention by giving a spiral form to the spring. 



Huygens would probably have continued in France 

 during the remainder of his life, had it not been for 

 the revocation of the edict of Nantz. He resolved to 

 remain no longer in a country where his religion was 

 proscribed, and its professors persecuted ; and, antici- 

 pating the fatal edict, he returned to his native country 

 in 1681. 



After his return to Holland, he continued to prose- 

 cute his favourite studies with his usual zeal. In 1684, 

 he published his Attroscopia Compendiaria lubi Optici 

 molimine liberata, in which he gives an account of a 

 method of using telescopes of great focal length, with- 

 out the incumbrance of a tube. He published also in 

 1690, at Leyden, his Trails de la Lumiere, and his Trac- 

 talus de Gravitate. The first of these works contains his 

 Theory of Light, which he supposes to be propagated 

 like sound, by the undulation of an elastic medium, t 

 and the beautiful law by which he represented all the 

 phenomena of double refraction as exhibited in Iceland 

 spar. The remainder of our author's life was occupied 

 in composing a work on the plurality of worlds, en- 

 titled Koe-^oSewjia;, sive de terris celcstibits, eorumque or- 

 natu conjecturte. While this work was in the printer's 

 hands, Huygens was seized with an illness, which 

 proved fatal on the 5th of June 1695. 



All his papers were bequeathed by his will to the 

 Library of Leyden, with a request that Burcher de Voi- 

 der and Fullenius, two excellent mathematicians, should 

 print such of them as seemed of most importance. 

 In the year 1700, this posthumous volume was pub- 

 lished. The Cosmotkeorios had appeared in 1698, and 

 was speedily translated into French, English, German, 

 and Dutch. In 1703, there appeared another posthu- 

 mous volume, entitled CHRISTIANI HUGKNII Dioptrica, 

 Descriptio Aidmnuli planelarii ; de parheliis, Opuscula 

 Poslluima. This work contains Huygens' interesting dis- 

 sertation on coronae, and mock suns, of which we have 

 given a short account in our article HALO, vol. x. p. 6'15, 

 and which was reprinted by Dr Smith in his Complete 

 Si/slem of Optics. A complete edition of the works of 

 Huygens was published, in four volumes, by M. 

 S'Gravesende. The two first appeared at Leyden in 

 1724, in 4to, entitled Opera Varia, and the two last 

 at Amsterdam in 1 728, entitled Opera Rdiqua. He pub- 

 lished also several papers in the early volumes of the 

 Philosophical Transactions, and in the Memoirs of the 

 Academy of Sciences. In the Machines Approuvtes par 

 I' Academic, torn. i. p. 71 and 72, he has published two 

 papers, one of which is entitled Machine pour\Mesurer la 

 force mouvanle de Fair ; and the other, Maniere d'empc- 

 cher les vaisseaitx de se briser lorsqu'il eckouenl. He also 

 published a letter on a new microscope, in the Collec- 

 tions Academiques, torn. i. p. 281 ; and another on the 

 Toricellian experiment, in the second volume of the 

 same work. 



Christian Huygens was unquestionably one of the 

 most eminent mathematicians and natural philosophers 

 of the age in which he lived. His application of the 

 pendulum to regulate the motion of clocks ; his beauti- 



* See HOROLOGY, p, 317. and Plate CCC. Fig. 4. 



f This doctrine has found an able supporter in Dr Thomas Young ; but recent discoveries respecting the polarisation of light, seem 

 to give a new degree of probability to the doctrine of the emanation of material particles. 



