MODERN THEORIES OF HEAT AND LIGHT 



But while all these affinities seemed so clear to the 

 great co-ordinating brain of Young, they made no such 

 impression on the minds of his contemporaries. The 

 immateriality of light had been substantially demon- 

 strated, but practically no one save its author accepted 

 the demonstration. Newton's doctrine of the emission 

 of corpuscles was too firmly rooted to be readily dis- 

 lodged, and Dr. Young had too many other interests to 

 continue the assault unceasingly. He occasionally 

 wrote something touching on his theory, mostly papers 

 contributed to the Quarterly Revieiv and similar period- 

 icals, anonymously or under pseudonym, for he had 

 conceived the notion that too great conspicuousness in 

 fields outside of medicine would injure his practice as a 

 physician. His views regarding light (including the 

 original papers from the Philosophical Transactions of 

 the Royal Society) were again given publicity in full in 

 his celebrated volume on natural philosophy, consisting 

 in part of his lectures before the Royal Institution, pub- 

 lished in 1807 ; but even then they failed to bring con- 

 viction to the philosophic world. Indeed, they did not 

 even arouse a controversial spirit, as his first papers 

 had done. 



ARAGO AND FRESNEL CHAMPION THE WAVE THEORY 



So it chanced that when, in 1815, a young French 

 military engineer, named Augustin Jean Fresnel, re- 

 turning from the Napoleonic wars, became interested 

 in the phenomena of light, and made some experiments 

 concerning diffraction which seemed to him to con- 

 trovert the accepted notions of the materiality of light, 

 he wa* quite unaware that his experiments had been 



