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XVIL NOTES ON SOME POINTS IN THE THEORY OF 



LIGHT. 



[Proceedings of the Royal Irish Academy, VOL. n. p. 139. Bead Nov. 8, 1841.] 



I. 



On a Mechanical Theory which has been proposed for the Explana- 

 tion of the Phenomena of Circular Polarization in Liquids, and 

 of Circular and Elliptic Polarization in Quartz or Rock-crystal; 

 with Remarks on the corresponding Theory of Rectilinear Pola- 

 rization. 



THE theory of elliptic polarization, which I feel myself 

 called upon to notice, was first stated by M. Cauchy, and has 

 been made the subject of elaborate investigation by other 

 writers. That celebrated analyst, conceiving (though without 

 sufficient reason, as will presently appear) that he had fully 

 explained the known laws of the propagation of rectilinear 

 vibrations by the hypothesis that the luminiferous ether, in 

 media transmitting such vibrations, consists of separate mole- 

 cules symmetrically arranged with respect to each of three 

 rectangular planes, and acting on each other by forces which 

 are some function of the distance, was led very naturally to 

 imagine that he would find the laws of circular and elliptic 

 vibrations, in other media, to be included in the more general 

 hypothesis of an unsymmetrical arrangement. Accordingly, 

 in a letter read to the French Academy on the 22nd of 

 February, 1836 a letter to which he attached so much im- 

 portance that he desired it might not only be published in 



