134 MICROSCOPIC OBJECTS. 



interest by mounting' in Canada balsam, that it would be 

 occupying too much space to enumerate them here ; it 

 affords also the best material for cementing sections of 

 shells, fossHs, &c., to glass slides. 



The method of applying the Canada balsam is as fol- 

 lows : — Warm the glass shps, &c. to a temperature just 

 below the boihng heat of water. If there is any doubt 

 of the balsam penetrating all the interstices and readily 

 adhering to the specimens, it will be well to pour a few 

 drops of clear turpentine upon the specimens, which 

 will greatly facilitate the taking of the balsam ; the lat- 

 ter, however, must not be used until the turpentine has 

 nearly evaporated. The moment when the balsam is to 

 be added with the best effect can only be known by 

 experience. Clear old Canada balsam is the best suited 

 for these purposes. When used it must also be heated 

 to a temperature just; below boihng water, and then 

 poured upon the object, previously arranged upon a slip 

 of glass. The top slip of glass, which is usually smaller 

 and thinner than the under one, is now to be placed upon 

 it ; one end of each slip being brought into contact fii'st, 

 and then the other allowed to fall upon it. By this 

 means no air-bubbles wiU be inclosed. The exact quantity 

 of balsam required must be learned by practice. Of two 

 faults, namely, too much or too little, the former is to be 

 preferred. 



Note. — Be careful not to press the glasses together 

 hard, otherwise, on the removal of the pressure, the air will 

 enter between the glasses and the preparation wiU be spoilt. 



