218 APPENDIX. 



merely as a hypothesis, acquires a considerable degree of 

 probability from the facts which 1 have stated, since I 

 have succeeded in rendering actually visible circular 

 particles of excessive minuteness, in each of which 

 the microscope detects the very structure imagined by 

 Brewster, viz. the black cross and four sectors of light. 

 So that it appears not improbable that the circular 

 polarizing properties of fluids may be owing to the 

 presence of multitudes of particles similar to these, which 

 they hold in solution. 



