26 AQUATIC MICROSCOPY TOR BEGINNERS. 



you think you are seeing some wonderful things, add a 

 drop of water and save yourself a probable blunder. 

 Certain objects, naturally dry, will look better and will 

 reveal their secrets sooner if examined wet. This is 

 ■due to optical reasons not necessary to explain here. 

 The observer, if he is seeking information, and not 

 merely pretty things to please the eye and the aesthetic 

 fancy, will do well if he examine naturally dry objects 

 both in and out of water; but things naturally wet 

 must never be seriously studied in a dry condition. 



The most convenient size for glass slips is three 

 inches in length by one in width. Some microscopists 

 use and recommend them two and one-half inches 

 long by one-half an inch wide, and this will probably 

 be the size of the slides accompanying the student's 

 stand. They are however, much too small; it will be 

 better for the beginner at once to select, the standard 

 size, three inches by one inch. These can be bought, 

 and the writer would advise that they should be, as the 

 edges will then be ground smooth and perhaps 

 polished, although the polish is not necessary. Slips 

 can be cheaply cut by any glass-dealer who has a dia- 

 mond or a glass-cutting wheel, and if thus made, the 

 best, whitest, smoothest, and thinnest glass should be 

 selected. The rough edges of these home-made slips, 

 however, are not pleasant to handle, the student who 

 uses them taking the risk of cut fingers. Otherwise, 

 unless they have a green color, they are as useful as 

 the more expensive ones sold by the dealers. 



A drop of water on a slip of smooth glass is not 

 easily kept in position. When the slide is placed on 

 the stage, and the microscope is inclined for use, as it 

 always should be, the water will surely run away, and 



