30 



THE AMEKICAN MONTHLY 



[February, 



no consequence if it be used only for 

 sealing the cells, and some more elas- 

 tic cement be used afterward to pro- 

 tect it. Shellac cement may be made 

 by dissolving shellac in alcohol, but to 

 get a clear solution the insoluble por- 

 tion must be allowed to settle, and 

 this requires days or weeks. It is 

 better, therefore, to purchase the solu- 

 tion from a paint shop, where it can 

 usually be obtained quite clear. A 

 few drops of castor oil to each ounce 

 of solution will improve it. It is well 

 to have two solutions of shellac, one 

 rather thick — as thick as it will flow 

 from the brush — and another much 

 thinner. 



Canada balsam is a most useful me- 

 dium if used with discretion. It has 

 been too generally employed, how- 

 ever, and many good specimens are 

 spoiled by mounting them in Canada 

 balsam. The balsam should be clear 

 and very slightly colored. It is well 

 to purchase two or three ounces from 

 a druggist for stock balsam, and after 

 taking out a small portion for imme- 

 diate use, place the bottle in a window 

 exposed to the sun. This will bleach 

 the balsam, and in a few weeks it will 

 be almost colorless. The best balsam 

 to buy is old balsam which is likely 

 to be tough and hard, but in case that 

 cannot be obtained soft balsam must 

 be hardened by heat. The best way 

 to prepare such balsam is to place it 

 in a wide-mouth bottle, covered 

 with paper to exclude dust, and set 

 the bottle in a dish of water on the 

 back of a stove where it will keep 

 warm but not become hot enough to 

 be uncomfortable to the hand. 



Test the balsam from time to time 

 by allowing a drop to thoroughly 

 harden on a slip of glass. When cold 

 it should resist the finger-nail but it 

 should not be brittle. 



From this balsam several prepara- 

 tions should be made : — 



1 . Benzole balsam . This is a rather 

 thick solution of the hardened balsam 

 dissolved in pure benzole. 



2. Chloroform balsam. This is 

 similar to the preceding solution. 



chloroform being used instead of ben- 

 zole. 



3. A thin solution in either benzole 

 or chloroform, which will run freely 

 from a brush. This is used in mount- 

 ing for making rings and finishing 

 slides. 



Excellent balsam, and solutions in 

 either of the above-named solvents, 

 can be obtained from dealers in mi- 

 croscopical materials. 



Damar is a mounting medium in 

 great favor with some persons, and is 

 an excellent substitute for Canada 

 balsam. It is used in solution, and 

 had best be purchased ready for use, 

 as it is rather troublesome to prepare. 



A material for mounting which has 

 been much condemned by many per- 

 sons, but which in our hands has al- 

 ways proved satisfactory, is wax. We 

 have used it very largely for mount- 

 ing opaque objects, selecting for the 

 purpose sheets of the dark, olive green 

 sold for making artificial flowers. It 

 is but just to add that the objections 

 raised against its use are sustained by 

 many high authorities. The great- 

 est objection is the tendency to the 

 condensation of minute drops upon 

 the cover-glass, obscuring the object. 

 Never having been troubled with this, 

 we shall describe the method of mount- 

 ing with wax in the course of these 

 articles. 



Glycerin jelly is an excellent me- 

 dium for mounting, especially for veg- 

 etable tissues. This had best be pur- 

 chased, although it is not especially 

 difficult to make. It is composed of 

 a solution of gelatin to which a certain 

 quanity of glycerin has been added. 

 The formula for preparing it will be 

 given if any reader desires it, in a fu- 

 ture article. 



White zinc cement has been much 

 used, and is, unfortunately, still em- 

 ployed, to some extent. It is a very 

 pleasing cement to work with, but all 

 we can say of it is that if the pre- 

 parer wishes to be assured that a cer- 

 tain proportion of his mounts will be 

 spoiled sooner or later by the running 

 in of the cement, let him use the white 



