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94 PREPARATION AND MOUNTING 
pressed down. When a number of balsam objects are being 
mounted at one time, the advantage of this plan in regard 
to facility and cleanliness (no superfluous balsam being 
deposited on the slide) will make itself sensibly felt,” but 
the collapsible metal capsules are certainly the best and 
most easily managed. 
When the mounting has been thus far accomplished, 
the outer wall of balsam may be roughly removed after a 
few hours have elapsed; but great care is necessary lest 
the cover be moved or disturbed in any way. In this 
state it may be left for the final cleansing until the balsam 
becomes hard, which takes place sooner or later, according 
to the degree of warmth to which it has been subjected. 
Many advocate baking in a slow oven to accelerate this 
drying; but with some objects even this heat would be 
too great, and generally a mantel-piece, or other place 
about equal to it in temperature, is the best suited 
to this purpose; and when the requisite hardness is 
attained, the slide may be finished as follows:—With a 
pointed knife the balsam must be scraped away, taking care 
that the thin glass be not cracked by the point getting 
under it. If used carefully, the knife will render the slide 
almost clean; but any minute portions which still adhere 
to the glass must be rubbed with linen dipped in turpentine 
or spirit. If the balsam is not very hard, these small 
fragments are readily removed by folding a piece of paper 
tightly in a triangular form with many folds, and damping 
the point with which the glass is rubbed. As the paper 
becomes worn with the friction, the balsam will be carried 
off with it. In some cases I have found this simple ex- 
pedient very useful. 
Sometimes the object to be mounted is of such a thick- 
ness as to require a cell. For this purpose glass rings are 
used (as described in Chapter V.), and filled with balsam. 
The best mode of doing this is thus described by Mr. T. S. 
Ralph in the Microscopic Jowrnal:—‘The question was 
asked me when I was in England, if I knew how to fill a 
