CEMENTS, VARNISHES, AND CELLS. 247 



its use is that it must be used quickly, the bottle must not be left 

 open, and it must not be too thin. Aside from its use in glycerine 

 mounts I only use white zinc as a finish. Some of you probably 

 remember the controversy between Mr. Hitchcock and Dr. Stowell 

 regarding the merits of white zinc. As I have a number of 

 mounts sent me by Dr. Stowell which have given out, I must add 

 my testimony to that of Mr. Hitchcock. However, until 

 something is found which will permanently confine glycerine, I 

 shall continue to use the white zinc, as I think it is the best 

 cement we now have for that purpose. If care is taken to remove 

 all traces of glycerine from around the edge of the cover before 

 the cement is applied, and each coat allowed to become thoroughly 

 dry before another is applied, you can expect a good mount. 



Other fluids than glycerine I seldom use. I find, however, 

 that one or the other of these three cements will confine almost 

 any fluid liable to be used. 



First on my list of varnishes is white zinc. This I use for its 

 colour alone, as it is apt to become brittle with age. My usual 

 finish is a broad ring of white zinc, with one or two narrow stripes 

 of Brunswick black. 



Brunswick black makes a very satisfactory finish, as it dries a 

 glossy black, and does not chip. It makes a very pleasant con- 

 trast with the white. 



Occasionally I employ a red varnish made by dissolving the 

 best red sealing-wax in alcohol. This gives a bright red varnish 

 that stands well. The best sealing-wax must be used, as the 

 cheaper kinds are britde. 



Shellac I use to varnish the insides of cells, and to support old 

 mounts that have begun to give way. Being colourless, it does 

 not destroy the individuality of the mount. By adding an 

 alcoholic solution of an anilin to a solution of orange lac, and 

 evaporating until of the proper consistency, a very brilliant varnish 

 may be made. If exposed to a strong light these varnishes are 

 apt to fade. 



For very shallow cells 1 employ gold size. If deep ones are 

 desired, I prefer wax, paper, and glass or metal rings. In a few 

 instances I have had good results from cells made of asphalt and 

 baked before being used. It is essential that the genuine asphalt 

 be used and not the coal-tar product. 



