EXAMINATION OF MARINE OBJECTS 95 



this aid, repeat with a higher power. This rule applies not only 

 to such small objects as we have now under consideration, but to 

 all objects, and parts of them, in which minute details are. to be 

 observed. 



Beginners with the microscope often find prolonged examination 

 very tiring to the eyes, but this, we believe, would seldom be the 

 case if right methods were followed. Both eyes should always be 

 open, and the microscopist should train himself to use both eyes 

 equally for the actual observation. 



The higher the magnifying power used, the nearer must the 

 objective (the lower combination of lenses) be brought to the object 

 itself, and it is no uncommon thing for the amateur, in his attempts 

 to focus his object, to lower the body of the microscope beyond its 

 proper position, causing the objective to crush the object, break the 

 thin cover-glass, and become wetted with the liquid, if any, in 

 which the object was being examined. All this may be avoided by 



FIG. 47. CELL FOR SMALL LIVING OBJECTS 



lowering the body of the microscope until it nearly touches the 

 cover-glass before attempting to view the object through it, and 

 then, with the eye above the object-glass, to gradually raise the 

 body until the object is in focus. 



The top of the cover-glass should always be perfectly dry; and 

 if by any chance the objective becomes wet it should be wiped 

 perfectly dry with a piece of old silk or with chamois leather. 

 Also, if permanent mounting is attempted, and the preservative 

 liquid is allowed to come in contact with the objective, such liquid 

 must, of course, be washed off with some suitable solvent before 

 any attempt is made to wipe the lens dry. 



If the object under examination is of such dimensions that the 

 cover-glass has a tendency to rock on it, or if it is a living object 

 of such a size that it is unable to move freely in the exceedingly 

 thin film of water between the cover and the slip, it should be 

 placed in a cell. The cell may be made by cementing a ring of 

 glass or vulcanite to the middle of a slip, or it may be a little 



