PREPARING AND MOUNTING. 217 



When thoroughly dry (which it will probably be in about 

 twenty-four hours, if in a warm room), separate the 

 glasses, and gently unfold the paper ; then, with a little 

 careful manipulation, the object may be readily detached, 

 and should be at once placed in a little spirit of turpentine, 

 where it should remain for a few days till it is rendered 

 transparent and fit for mounting. The time during which 

 it should remain in this liquid will depend on the struc- 

 ture ; some objects, such as wings of flies, will be quickly 

 permeated, while horny and dense objects require an 

 immersion of a fortnight or even longer. A pomatum pot 

 with a concave bottom and well-fitting lid will be found 

 to answer admirably for the soaking process, and it is 

 well, in preparing several specimens at a time, to have two 

 pots, one for large and medium, the other for very small 

 objects, or the smaller ones will be found often to adhere 

 to the larger. 



The glasses on which objects are mounted are usually 

 slips of flatted crown or sheet glass cut to a size of three 

 inches by one, and ground at the edges. The mode ot 

 mounting the object is as follows : Having chosen a glass 

 slide, clean and polish it with a piece of chamois leather, 

 ascertain the centre of the slide by means of a piece of 

 paper or card of exactly the same she as itself, and in 

 which a hole has been cut exactly in the centre, 

 place the piece of paper under the slide, and, having 

 removed the object to be mounted from the turpentine in 



Fig. 139. Showing the mode of placing Glass Cover on th Object. 



which it has been soaked, lay it on the slide on the spot 

 corresponding to the hole in the card underneath ; then 

 tain up a small quantity of the prepared Canada balsam 

 on the point of a large needle or pointed pen-knife, and 



