Di 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 

 <.V,btly in a triangular form with many folds, and damping 

 Ih? 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- 

 r.ess as to require a cell. For this purpose glass rings are 

 nsed (as described in Chapter V.), and filled with balsf m. 

 The best mode of doing this is thus described by Mr. T. S. 

 Halph in the Microscopic Journal : " The question was 

 asked me when I was in England, if I knew how to fill a 



