114 B. MOIILAND ON MOUNTING MEDIA FOR DIATOMS. 



but, to my astonishment, on trying to dissolve the sulphur in 

 the aniline I found it to be insoluble, though a friend of mine, a 

 chemist, tells me that sulphur dissolves freely in aniline- 

 Under these circumstances I am unable to give any opinion on 

 this medium, further than that if the solution can be prepared 

 and permanently sealed on a slide it ought to be satisfactory 

 so far as regards the refractive index, but has the objection of 

 beinor a fluid. 



A medium of high refractive index is certainly a desideratum, 

 but it must be permanent, and if one could be discovered which 

 could be prepared and manipulated by any microscopist not 

 having special knowledge of chemistry, why so much the 

 better. On the other hand, it is a comfort to the ordinary run 

 of diatomists to know that there are really only few diatoms 

 that absolutely require such high refractive media. 



