OF MICROSCOPIC OBJECTS. 95 
cell with Canada balsam and leave behind no air-bubbles ? 
I replied in the negative; but now I can state how to 
accomplish this. Fill the cell with clear spirit of turpentine, 
place the specimen in it, have ready some balsam just fluid 
enough to flow out of the bottle when warmed by the hand; 
pour this on the object at one end, and gradually inclining 
the slide, allow the spirit of turpentine to flow out on the 
opposite side of the cell till it is full of balsam; then take 
up the cover, and carefully place upon it a small streak of 
Canada balsam from one end to the other. This, if laid on 
the cell with one edge first, and then gradually lowered 
until it lies flat, will drive all the air before it, and prevent _ 
any bubbles from being included in the cell. It can be 
easily put on so neatly as to require no cleaning when 
dry. If the cover be pressed down too rapidly, the balsam 
will flow over it, and require to be cleaned off when 
hardened, for it cannot be done safely while fluid at the 
edges.” 
Sometimes with every care bubbles are enclosed in the 
balsam, injuring objects which are perhaps rare and valuable. 
Tf the object will not be injured by heat, carefully warming 
the slide over a lamp will often set loose and remove these 
pests; but should heat be objectionable, or the bubbles too 
closely imprisoned, the whole slide must be immersed in 
turpentine until the cover is removed by the solution of the 
balsam; and the object must be cleansed by a similar steep- 
ing. It may then be remounted as if new in the manner 
before described. 
The balsam and chloroform described in Chapter II. is 
thus used; and where the object is thin, the mounting is 
very easily accomplished. When the object is laid upon the 
slide with a piece of glass upon it, and the balsam and 
chloroform placed at the edge of the cover, the mixture will 
gradually flow into the space betwixt the glasses until the 
object is surrounded by it, and the unoccupied portion filled. 
The chloroform will evaporate so quickly that the outer edge 
will become hard in a very short time, when it may be 
