Notes on some Points in the Theory of Light. 201 



which I used was, in fact, identical with that theory, in the 

 most general form of which it is susceptible, when unrestricted 

 by any particular supposition as to the arrangement of the 

 ethereal molecules; and therefore the fundamental conception 

 of the theory could not be true, as it not merely failed to ex- 

 plain a large and most remarkable class of phenomena those 

 of circular and elliptical polarization but absolutely excluded 

 them, and left no room for their existence. It followed from 

 this, that the mechanical explanation, which the same theory 

 was supposed to have given, of the phenomena of rectilinear 

 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 reasons, of which one has been already men- 

 tioned, and another was suggested by the forced relations which 

 M. Cauchy had found it necessary to establish among the con- 

 stants of his theory, and by which he had compelled, as it were, 

 his complicated formulas to assume the appearance of an agree- , 

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

 laws of Fresnel. 



Such were the conclusions at which I arrived, and the re- 

 flections 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 ;* 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 

 whether from the real difficulties 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 mathe- 

 matician 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 



* Transactions, R. I. A., VOL. xvm. p. 68 (supra, p. 129). 



