48 The Microscope. 



pose for which dammar solution is necessar\\ In rubbing up 

 the residue of the first and second decantations, observe the 

 same rules as to quantity treated each time as in making the 

 original mixture."^ 



Dr. James seems not to use gum mastic as one of the ingred- 

 ients. This, however, is included in all the formulae for the 

 cement as made and used by the dealers in Europe. Dr. James, 

 in his " Microscopical Technology," again says in reference to 

 this : " There is in my opinion no cement which can compare 

 with it, either in the smoothness with which it flows from the 

 pencil, rapidity of drying, tenacity and evenness of attachment, 

 or the hardness and toughness of the product. In addition to 

 these practical recommendations, there is nothing in the way of 

 cements that is more beautiful in finish. In saying this much 

 about the cement, I am quite aware that it has been decried and 

 abused by certain parties, belonging to that class of workmen 

 who invariably lay their own lack of skill upon the tools they 

 use. I have used it constantly for fifteen years, and whenever 

 it has failed to make a good and durable mount the failure could 

 be traced directly to my own negligence or carelessness." 



This is strong evidence in favor of the material, and I am 

 glad that I have never even attempted to use it, preferring 

 another kind that has rarely played me false. In condemning 

 the white zinc cement I have not to blame myself for any lack 

 of skill, nor for carelessness, as all my slides made with the 

 material have been prepared b3' others. 



But while writing this I have received a mount made by A. 

 C. Cole, of London, a celebrated preparer. The slide is finished 

 and the cell is made with white zinc cement. It is an interest- 

 ing fact in connection with my criticisms, that this slide from 

 this well-known preparer is acting as similar mounts alwa3^s 

 have acted and always will act. The cement is .beginning to 

 leave the glass. For at least one-half of the circumference of 

 the cell the ring is separating spontaneously from the slip, and 

 in time the separation will be complete. 



BENZOL, BENZINE AND GASOLINE. 



Benzol has already been mentioned several times and will be 

 mentioned probably several times more, as it is an import men- 



*Dr. F. L. James, in "The National Druggist." 



