LECTURE VJIT. 

 ON LIGHT. 



PART III. DOUBLE REFRACTION POLARIZATION. 



|N that most wonderful work, the Optics of 

 Sir I. Newton, among the queries annexed 

 at the end, occurs this very singular one: 

 " Have not the rays of light different sides, 

 endued with different original properties?'"* The con- 

 ception intended to be conveyed, as further illustrated 

 by Newton himself, embodies that abstract notion of 

 polarity which Dr Whewell in his " Philosophy of Induc- 

 tive Science," expresses by " opposite qualities in oppo- 

 site directions," or, as we should prefer to say, for this 

 purpose, " different qualities in different directions," with 

 reference (that is) to surrounding space and the objects 

 therein situated. The same form of the general concep- 

 tion, as regards light, which Newton employed to desig- 

 nate the very same peculiarity in its habitudes, was 

 adopted by Malus in his first announcement of the re- 

 " Opucs," Book iii., Query 26. 4th Edition. 



