637 



HUYGHENS, CHRISTIAN. 



HUTSUM, JOHN VAN. 



6.38 



Condorcet, were displeased at this step, which may have been the 

 case, since his father was a strong partisan of the French. (' Biog. 

 Univ.," art. ' Const. Huyghens.' The same writer says it was 

 reported at Paris that he wrote verses ('assez mauvais') to Ninon 

 de L'Enclos. 



The greater part of the works of Huyghens which were published 

 during his lifetime were collected into four volumes by S'Gravesande, 

 under the title of ' Chriatiani Hugenii Zuliehemii dum viveret Zelemii | 

 Toparehjc, Opera Varia,' Lugd. Bat, 1724. But Huyghens left his 

 papers to the University of Leyden, with the request that two pro- 

 fessors, De Voider and Fullen, would select and publish what they 

 thought fit The consequence was a volume entitled 'Christian! 

 Hugenii, &c., Opuscula Posthuma,' Amsterdam (?), 1700. But in 1728 

 S'Gravesande completed his edition of the works printed by Huyghens 

 himself, and also re-published the ' Opuscula Posthuma : ' this edition, ! 

 entitled ' Opera Reliqua,' was printed at Amsterdam. To these two 

 works, which contain almost all that Huyghens wrote, and all that he 

 published, with the exception of papers in the 'Philosophical Trans- 

 actions ' and other periodicals, we must add the mention of his 

 correspondence, published under the following title : ' Christ 

 Hugenii aliorumque Exercitationes Mathematics et Philosophise ex 

 M!?S. in Bibl. Acad., Lugd. Bat, erlente P. J. Ujlenbroek,' Hag. Com., 

 1833, &c. Weidler also mentions a volume of posthumous works 

 published at Leyden in 1703. Wo shall presently notice the several 

 writings of Huyghens, first observing that he occupies a most con- 

 spicuous place among the immediate precursors of Newton : had it 

 not been known that Newton was in possession of at least the main 

 points of his system before 1674 it would undoubtedly have been fail- 

 to suppose that the researches of Huyghens gave most material 

 suggestions to the investigator of the theory of gravitation. His 

 writings seem to form the natural and proper step in the chain 

 between those of Galileo and Newton. 



We shall give the list of Huyghen's works in the order of subjects, 

 with a short description of what ia now memorable in each. 



I. Geometrical Works. 



' Theorcmata de Quadrature Hyperboles, Ellipsis, et Circuli, ex 

 clato portionum Gravitatis Centro; quibus subjunuta est 'E{eVa<ns 

 Cyclometriac CL Viri Gregorii ii S. Vincentio,' Lugd. Bat, 1651. The 

 theorems have more merit than use: it is to be remembered that they 

 followed the work of Guldinus. [GuLDixua] The answer to the 

 quadrature of the circle by Gregory of St. Vincent will bo further 

 uuted in the article on that subject. 



'De Circuli Magnitudine inventiX. Accedunt ejusdem Problematum 

 quorundam illustrium Constructions,' Lugd. Bat, 1651. In tMs 

 work Hnyghens gives some new and very close approximations to the 

 quadrature of the circle ; he was also engaged in a controversy with 

 James Gregory on this subject, for the details of which see 'Journal 

 des Scavana,' July and November 1668, and ' Phit Trans.,' Nos. 37 

 and 44. There are some minor geometrical writings of Huyghens in 

 the ' Divers Ouvrages de Mathdmatique et de Physique,' Paris, 1693. 



II. Mechanical Works. 



' Horologium,' Hag. Com., 1658, and ' Horologium Oscillatorium, 

 Eive de Motu Pendulorum a Horologia aptato Demonstrations 

 Geometrica:,' Parisiis, 1673. In the first of those tracts Huyghens 

 simply describes the application of the pendulum to the clock, of 

 which improvement he is the inventor. The idea came to him in 

 1656, and the pendulum employed was the common circular one. In 

 the second he describes the well-known but now disused apparatus by 

 which the geometrically isochronous or cycloidal pendulum was 

 obtained. But this is the least part of the celebrated work before 

 ns, which contains four distinct and new discoveries of first-rate 

 importance. The first is that of the cycloid being the curve ; all 

 whose arcs measured from the lowest point are synchronous. The 

 second is the invention of the involution and evolution of curves, in 

 which the proposition is established that the cycloid is its own 

 evolute. The third is the method of finding the centre of oscillation, 

 being the first successful solution of a dynamical problem, in which 

 connected material points are supposed to act on one another. The 

 fourth is the announcement (without demonstration) of those relations 

 between the centrifugal force and velocity of a body revolving in a 

 circle, which were afterwards proved in the ' Principia,' It thus 

 appears that Huygheus was in complete possession of the solution of 

 the problem of circular motion : had his mind not been pre-occupied 

 by the C irt-*ian system, it is most probable that he would have gone 

 at least to the extent of deducing Kepler's laws from the assumption 

 of gravitation. Demonstrations of the theorems on centrifugal force 

 were found among his papers, and published in the ' Opera Keliqua.' 

 It ia possible that these might have been written after he had seen 

 the ' Principia 1 of Newton. 



The publication of the treatise above mentioned drew on a con- 

 troversy with the Abbe' Catelan, in which John Bernoulli, De 

 L'Hupital, and others took part 



In the ' Journal dea Scavans,' February 1675, Huyghens described 

 the spring pendulum, such as ia now used in watches. Though there 

 can be no doubt that this was an independent invention, yet its priority 

 has been questioned. 



Huyghens was one of the first who gave the laws of impact; the 

 Koyal Society of London, had invited attention to the question, and 



Huyghens, Wren, and Wallis aent solutions to the Royal Society about 

 the same time (1669). There is an extract from his paper in the 'Phil. 

 Trans.' for that year ; but the whole paper (perhaps enlarged) appears 

 among the posthumous works. 



The treatise ' Sur la Cause de la Pe"santeur ' was first printed in 

 French (Leyden, 1690), at the end of the 'Traitd de la Lumiore.' Both 

 are Latiuistd in the ' Opera Reliqua.' There are several minor pieces 

 on different problems of mechanics. 



III. Astronomical Works. 



'De Saturui Luna Observatio Nova," Hag. Com., 1656. This is a 

 tract of two pages printed at the end of Horelli, ' De vero Telescopii 

 Inventore.' It announces the discovery of a satellite to Saturn, 

 beiug that which we now call the fourth. This took place on the 

 25th day of March 1665, and Huyghens immediately (as was then 

 common) communicated the following cipher: "Admovere oculis 

 distantia sidera uostris vwvvwcccrrhnibqx;" which being 

 transposed will make the following: "Saturno luna sua circum- 

 ducitur diebus sexdecim horis quatuor." In the present tract he 

 explains this enigma, and adds that he is about to publish on tho 

 Saturnian system. In the meanwhile he adds another logogryph to 

 substantiate hia right to another discovery ; it is as follows: " a a a a 

 aaacccccdeeeeeghiiiiiiillllmmnnnnnnnnnoooopp 

 grr ttttttuuuitu." The explanation of this dark saying was 

 given in the 'Systema Saturnium,' printed at tho Hague in 1759. It 

 should be remembered that Galileo's telescopes showed him nothing 

 more as to Saturn than that it appeared to have some lateral appen- 

 dages which looked like handles. In 1655, Huyghens had applied 

 himself, in conjunction with his elder brother Constantino, to the 

 manufacture of large telescopes. The meaning of the enigma waa, 

 Aunulo cingitur tenui, plauo, nusquam cohserente, ad eclipticam 

 inclinato ; that ia, he had discovered Saturn's ring. The ' Systema 

 Saturnium ' gives an account of the discovery, fixes the position of 

 the ring, and explains the phenomena of its appearance and disap- 

 pearance, &c. This work also occasioned some controversy, now 

 forgotten. It is worth while to take notice that Huyghens was pre- 

 vented from looking for any more satellites by the notion, then not 

 uncommon, that the whole number of satellites in the solar system 

 could not exceed that of the planets. 



The ' Cosmotheoros ' was passing through the preas when Huygheus 

 died. It was printed at the Hague in 1698, and waa twice printed 

 in English, first in 1698, and next at Glasgow in 1757; besides several 

 translations into continental languages. It defends tho Coperuicau 

 system, and enters into a large number of speculations on the physical 

 constitution and probable inhabitants of the planets. 



IV. Optical Works. 



These are the 'Traite 1 de la Lumiere," Leyden, 1690, Latinised in 

 the ' Opera Reliqua ;' the Dioptrics, and the ' Commentarii de Vitris 

 Figurandis," both first given in the poathumous works. The first 

 treatise was reprinted by Baron Maseres in his ' Scriptores Optici,' 

 London, 1823. It was written in 1678, and must now be considered 

 as the 'Principia' of optics. Huyghens took up the theory of undu- 

 lations in opposition to that of emanation, which was adopted by 

 Newton. By this theory he gave a sufficient explanation of the pheno- 

 mena of reflexion and refraction, and also of that of double refraction, 

 in wliich Newton could not succeed ; that is, he gave an explanation of 

 all the prominent phenomena of optics. The undulatory theory is now 

 almost universally received, and Huyghens must be considered as the 

 founder of it ; for though Hooke had previously advanced the notion, 

 yet he made no application of it to the explanation of phenomena. 



It remains to mention the treatise 'D^RatiociniisinLudoAleas/which 

 was printed at the end of Schooten's ' Exercitationes Matheinaticoe,' 

 Leyden, 1657. It is the earliest regular treatise on questions of 

 chances, and first points out the manner in which the expectation of a 

 player is determined. Some minor writings we leave unnoticed. 



As a philosopher, Huyghens is distinguished by correctness, pene- 

 tration, and a freshness of iutcllect which never left him. Before he 

 was in possession of the formal differential calculus he was able to 

 supply its place. His power of acquisition lasted to the end of his life. 

 He was near sixty when he read the 'Principia,' and past that age 

 when he began to study the Calculus of Leibnitz. At that time of 

 life persons seldom change old opinions, but Huyghens admitted the 

 theory of Newton instantaneously; ami he was probably the first 

 continental philosopher who published his adhesion to the theory of 

 gravitation, not generally, but after minute examination. 



HUYSUM, JOHN VAN, born at Amsterdam in 1682, was tho most 

 eminent painter of flowers and fruit in the 18th century. His father, 

 a picture-dealer and painter, was the instructor of his son, who at an 

 early period resolved to devote himself entirely to that branch of the 

 art in which he attained such unrivalled eminence. Every term of 

 panegyric that language can furnish has been lavished, and with justice, 

 on his productions ; he seems to have dived into tho mysteries of nature 

 to represent the loveliest and most brilliant of her creations with all 

 the magic of her own pencil. His flowers however are more beautiful 

 and true to nature than his fruits. He is equally successful in the 

 accessories ; the drops of dew, the insects, birds' nests, with their eggs 

 and feathers, are all painted so as almost to deceive the eye. The vases' 

 in which he puts his flowers are always from some elegant model, and 

 tho bas-reliefs are finished with the same exquisite care. He was the 



