KINETIC OR MECHANICAL VIEW OF NATURE. 21 



emancipate himself from the astronomical view of 

 phenomena. In France the matter stood quite difierently, 

 and nothing hetter proves the genius of Augustin Fresnel 1.5. 



. . . AuKUBtin 



than the fact that he ventured against the opp(Jsition of FrcHnei. 

 great authorities to go his own way, starting from the 

 beginning and devising many ingenious appeals to nature 

 herself — i.e., to experiment — in order to establish a 

 correct view. It is well known that his labours had to 

 wait many years for their deserved appreciation.^ It is, 

 however, only just to remark that Arago, an admirer of 

 Laplace and an intimate friend of Biot, the great 

 supporter of the projectile theory of light, was the first 

 to recognise the importance of Fresnel's work, and that 

 it was largely owing to his co-operation and influence 

 that the undulatory theory of light trimnplied in the end. 

 Fresnel's own labours began with the study of the 

 same phenomena which had led Young to the discovery 

 of " interference " — -viz., the bands and coloured fringes 

 observable round the shadows of small screening objects, 

 or the images of small apertures through which rays of 

 light are allowed to enter : the phenomena of diftraction 

 or inflection of light. But whilst Young still explained 

 these phenomena as arising from the interference of 

 direct " portions " of light and such as were reflected at 

 the edge of the screening obstacle, Fresnel showed th.iL the 

 principle of interference had a much wider application, that 

 it was adequate to exphiin why a periodic wave-motion, 

 such as was conceived by Huygens, only sent out rays of 



experiment, since he has not de- 

 monsstratod that a similar coinci- 

 dence might not be obtained by 

 proceeding on totally different 



grounds" ('Quarterly Review,' No. 

 l,p. 109). 



' See the first volume of this 

 work, p. 241 note'-. 



