112 The Luminiferous Medium, 



angle of 5245' has all the characteristics of one of the beams 

 produced by the double refraction of Iceland spar, whose 

 principal section is parallel to the plane which passes through 

 the incident ray and the reflected ray. If we receive this 

 reflected ray on any doubly- refracting crystal, whose principal 

 section is parallel to the plane of reflexion, it will not be divided 

 into two beams as a ray of ordinary light would be, but will be 

 refracted according to the ordinary law." 



After this Malus found that light which has been refracted 

 at the surface of any transparent substance likewise possesses 

 in some degree this property, to which he gave the name 

 polarization. The memoir* which he finally submitted to the 

 Academy, and which contains a rich store of experimental and 

 analytical work on double refraction, obtained the prize in 1810 ; 

 its immediate effect as regards the rival theories of the ultimate 

 nature of light was to encourage the adherents of the corpuscular 

 doctrine ; for it brought into greater prominence the phenomena 

 of polarization, of which the wave-theorists, still misled by the 

 analogy of light with sound, were unable to give any account. 



The successful discoverer was elected to the Academy of 

 Sciences, and became a member of the celebrated club of Arcueil.f 

 But his health, which had been undermined by the Egyptian 

 campaign, now broke down completely : and he died, at the age 

 of thirty-six, in the following year. 



The polarization of a reflected ray is in general incomplete 

 i.e. the ray displays only imperfectly the properties of light 

 which has been polarized by double refraction ; but for one 

 particular angle of incidence, which depends on the reflecting 

 body, the polarization of the reflected ray is complete. Malus 

 measured with considerable accuracy the polarizing angles for 

 glass and water, and attempted to connect them with the other 

 optical constants of these substances, the refractive indices and 

 dispersive powers, but without success. The matter was 



* Mem. presentes a 1'Inst. par divers Savans, ii (1811), p. 303. 



t So called from the village near Paris where Laplace and Berthollet had 

 their country-houses, and where the meetings took place. The club consisted of 

 a dozen of the most celebrated scientific men in France. 



