THE MICROSCOPE. 159 



keep out dust, but do not use any cover-glass. In a short time 

 (from one to two hours), the whole will be a mass of crystals. 

 Let them dry in the air and then mount in benzole balsam. 

 Most of these crystals are brilliant polariscopic objects but per- 

 haps a few will not polarize. Triple phosphates do not settle 

 but form a film on the surface; this film can be transferred to the 

 slide with a spatula and be treated as above directed. The path- 

 ological significance of these crystals can be learned by consult- 

 ing the plates of the numerous works devoted to medical mi- 

 croscopy. 



Sections of Potato. — A very good and instructive sec- 

 tion of potato can be made with a razor. Trim away the 

 thick parts and place the thin section in the center of a slide. 

 Flood with alcohol in order to dry the specimen. This flood- 

 ing will wash out a great deal of the starch from the cells and 

 leave other cells full. This washing increases the interest of the 

 slide, as thereby you can contrast the empty cells with the 

 others. When perfectly dry, mount in balsam and view by po- 

 larized light. It is an interesting specimen with ordinary light, 

 but its beauty is enhanced a thousand fold by polarization. Do 

 not stain the specimen. Beauty is, when unadorned, adorned 

 the most. Staining will only destroy the natural beauty of the 

 object. 



How to Examine a Water Supply. — Tie a small bag 

 over the spigot of a wash basin and let the water run 

 until the bag gets like a sausage; then remove and empty it in- 

 to a conical glass; and when it has settled, examine the contents. 

 Always turn the bag wrong side out and wash it into the wa- 

 ter you desire to examine. Some of the best specimens adhere 

 closely to the cloth and even stick in its meshes. Any cloth of 

 fine texture will answer. The little cloth sacks in which smok- 

 ing tobacco is put up for sale will answer the purpose well. If 

 the bag be too large, too thick, or too thin, it will not work well. 

 The spigots over the sink in kitchens are too large and do not 

 give satisfactory results. There are also a number specimens 

 that habitually rise to the top and this top should always be 

 examined. On the surface will be found some of the rarest 

 specimens. First examine the top in a cell and with an inch 

 objective. The examination of water is interesting at all times 

 of the vear. 



