LECTURE VIIL 

 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- 



* " Optics," Book iii., Query 26. 4th Edition. 



