72 ‘HE MICROSCOPE. 
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 zine. 
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 
glycerin, 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 glycerin 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 glycerin 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 color 
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 Bruns- 
wick black. 
Brunswick black makes a very satisfactory finish, as it dries a 
glossy black, and does not chip. It makes a very pleasant contrast 
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 brittle. 
Shellac I use to varnish the insides of cells, and to support old 
mounts that have begun to give way. Being colorless 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 I employ gold size. If deep ones are 
desired, I prefer wax, paper, and glass or metal rings. In afew 
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. 
Cement cells must be built up one coat at a time. If the second 
coat is added before the first is perfectly hard, the cell will eventually 
break down. 
The best cell that I have found for dry mounts is made by 
punching a hole in a piece of blotting paper of the proper size and 
