302 ON THE STRUCTURE, &C» 



light is transmitted in one direction, and two bright images, when the light is 

 transmitted in another direction ; but it possesses this property under circum- 

 stances of such an extraordinary nature, that I could not with propriety hare 

 introduced any account of it into this paper. 



A number of soft substances, of animal and vegetable origin, have likewise 

 the faculty of forming a bright and a nebulous image, under various singular 

 modifications. A full account of the results which I have obtained with this, 

 class of substances, will be foimd in another pi^er. 



XL 



