KINETIC OR MECHANICAL VIEW OF NATURE. 9 



There is not, indeed, to be found in Fresnel's work any 

 central and simple formula like the gravitation formula 

 of Xewton out of which everything else flows with 

 mathematical necessity. His work lay rather in combin- 

 ing a number of fruitful suggestions thrown out by 

 contemporary or earlier writers into a consistent whole, 

 correcting and enlarging them as was found necessary, 

 and following them out into their logical consequences. 

 Thus he was able to reveal in a special branch of physical 

 science new phenomena which had remained unobserved 

 or unexplained till that time. In order to understand 

 how the kinetic view of nature has become firmly estab- 

 lished in the minds of physicists it will be useful to enum- 



In a certain sense Euler carried 

 further the work of Huygens, . . . 

 but aa he neglected the useful idea 

 of a wave-surface and anxiously 

 avoided Huygens' principle, he 

 made the theory which he wished 

 to defend unfruitful. . . . We think 

 that Euler did more harm than 

 good to the progress of that theory. 

 . . . Euler's theory of light had no 

 great number of followers." In 

 England Euler's theory was known 

 and generally condemned. Priest- 

 ley, in his ' History of Optics ' 

 (1772), refers to it at some length. 

 In the well-kuown attacks in which 

 Lord Brougham treated so unfairly 

 and superficially the discoveries of 

 Dr Young, it is suggested that the 

 latter borrowed his ideas from 

 Euler, whose natural philosophy is 

 held in little esteem. The fact is 

 that Young really went back to 

 Huygens and Newtou, and that he 

 well knew that his own opinion, 

 as stated in the first Bakerian 

 Lecture (1802), "was precisely the 

 theory of Hooke and Huygens, with 

 the adoption of some suggestions 



made by Newton himself as not in 

 themselves improbable " (Young's 

 ' Miscellaneous Works,' ed. Peacock, 

 vol. i. p. 200). In spite of the 

 great admiration which Young had 

 for Euler as a mathematician, he 

 admits that Euler "added no 

 argumentative evidence whatever to 

 the [undulatory] theory, but has 

 done a real injury to the cause 

 which he endeavoured to support " 

 (' Lectures on Natural Philosophy,' 

 ed. Kelland, voL i. p. 380). A more 

 recent and well-informed writer on 

 this subject, M. Verdet, says of 

 Euler : " Bien qu'il a donne de la 

 plupart des phenomenes connus de 

 son temps les explications les plus 

 inexactes, il ne merite pas moins de 

 conserver dans 1'histoire de 1'optique 

 une place e"minente pour avoir dit 

 d'une maniere expresse que les 

 undulations lumineuses sent peViod- 

 iques comme les vibrations sonores, 

 et que la cause des differences de 

 coloration est au fond la meme, que 

 la cause des differences de tonalite* " 

 ('(Euvres de Fresnel,' vol. i. p. 

 xix). 



