CH. XXXII. THE POLARIZATION OF LIGHT. 311 



divided ray which has passed through Iceland spar. Light 

 reflected from other substances is also divided up in this 

 way, only the angle at which this change takes place is dif- 

 ferent for each different substance. Malus was the first to 

 call this peculiar ^^qq.\, polarization^ and light which behaves 

 in tliis way has since been always called ' polarized light.' 



His discovery led to a completely new study, for people 

 had almost forgotten the experiments which had been made 

 by Huyghens more than 100 years before ; but this novel and 

 curious fact attracted attention, and the subject was taken up 

 again. Malus did not live to explain the matter ; he found 

 out many remarkable facts about it, but it was Young and 

 the French philosopher Fresnel who really worked out the 

 theory of the polarization of light. 



Polarization of Light explained by Young and Fresnel. 

 1816. — Augustin Fresnel, the contemporary and friend of 

 Thomas Young, was born at Broglie, in France, in 1788. 

 He was a delicate backward boy, who disliked books, but 

 loved practical experiments, and he followed his tastes by 

 becoming an engineer. Being a Royalist, however, he was 

 harshly treated by the Empero%Napoleon L, and he retired 

 to Normandy to devote himself to science. He died of 

 consumption in 1827. 



It is very difficult to decide whether Young or Fresnel 

 was the first to point out how certain peculiar vibrations of 

 the ether explain the polarization of light. But fortunately 

 this need not trouble us, for the men themselves were not 

 anxious to dispute about their claims. Young's discoveries 

 were very coldly received in England, for very few men un- 

 derstood them ; and unfortunately Lord Brougham wrote 

 many severe articles against them in the ' Edinburgh Review,' 

 which made people think they were only foolish specula- 



