HISTORY OF OPTICS. 



neither of the rays was refracted according to the 

 ordinary law, though it had hitherto been supposed 

 that one of them was so ; a natural inaccuracy, 

 since the errour was small 10 . Thus this beautiful 

 theory corrected, while it explained, the best of the 

 observations which had previously been made ; and 

 offered itself to mathematicians with an almost 

 irresistible power of conviction. The explanation 

 of laws so strange and diverse as those of double 

 refraction and polarization, by the same general 

 and symmetrical theory, could not result from any- 

 thing but the truth of the theory (LA). 



"Long," says Fresnel 11 , "before I had conceived 

 this theory, I had convinced myself, by a pure con- 

 templation of the facts, that it was not possible to 

 discover the true explanation of double refraction, 

 without explaining, at the same time, the pheno- 

 mena of polarization, which always goes along with 

 it ; and accordingly, it was after having found what 

 mode of vibration constituted polarization, that I 

 caught sight of the mechanical causes of double 

 refraction." 



Having thus got possession of the principle of 

 the mechanism of polarization, Fresnel proceeded 

 to apply it to the other cases of polarized light, 

 with a rapidity and sagacity which reminds us of 

 the spirit in which Newton traced out the conse- 

 quences of the principle of universal gravitation 



10 An. Ch. xxviii. p. 264. 



11 Sur la Double Rcf., Mem. Inst, 1826, p. 174. 



