14T 



which the same theory was supposed to have given, of the 

 phenomena of rectiUnear polarization and double refraction 

 in crystals, could not be well founded ; indeed, as I have 

 said, I had always distrusted it, and that for various rea- 

 sons, of which one has been already mentioned, and another 

 was suggested by the forced relations which M. Cauchy had 

 found it necessary to establish among the constants of his 

 theory, and by which he had compelled, as it were, his com- 

 plicated formulas to assume the appearance of an agreement 

 (though, after all, a very imperfect one) with the simple laws 

 of Fresnel. 



Such were the conclusions at which I arrived, and the 

 reflections which they forced upon me, nearly six years ago. 

 They have been frequently mentioned in conversation to 

 those who took an interest in such matters, and their general 

 tenor may be gathered from what I have elsewhere written 

 (Transactions of the Academy, vol. xviii. p. 68); but I did not 

 think it worth while to publish them in detail, because it seemed 

 probable that juster notions would prevail in the course of a 

 few years, and that the ingenious speculations to which I 

 have alluded would gradually come to be estimated at their 

 proper value. But from whatever cause it has arisen — whe- 

 ther from the real diflSculties of the subject, or the extreme 

 vagueness of the ideas that most persons are content to form 

 of it, or from deference to the authority of a distinguished 

 mathematician — certain it is that the doctrines in question 

 have not only been received without any expression of dissent, 

 but have been eagerly adopted, both in this country and abroad, 

 by a host of followers; and even the extraordinary error, which 

 it is my more immediate object to expose, has been continually 

 gaining ground up to the very moment at which I write, and 

 has at last begun to be ranked among the elementary truths of 

 the undulatory theory of light. Notwithstanding my unwilling- 

 ness, therefore, to be at all concerned in such discussions, 

 I do not think myself at liberty to remain silent any longer. 



