138 PREPAEATION AND MOUNTING 



the edges can be thus cleaned perfectly enough for any 

 cement to adhere. Mr. Suffolk, at the Quekett Club, said : 

 When the cell was closed he varnished it with a coating 

 of common liquid-glue, and when this was dry he put it 

 under the tap and thoroughly washed it, in order to remove 

 any glycerine which might remain outside. After carefully 

 drying the slide with blotting-paper, he gave it another 

 coating of the liquid -glue, and when dry repeated the wash- 

 ing process, and after having given it a third coating of 

 liquid-glue in the same manner, he gave it a final coat of 

 gold-size, and he never had any trouble with cells closed in 

 this manner. Mr. Hislop, at the same place, said : His 

 plan was, to make a good seat for the cover first by a thick 

 ring of gum dammar allow this to become sticky; next 

 put in the glycerine, lay on the cover, and then carefully 

 wash off all superfluous glycerine. When perfectly well- 

 washed and dried lay on two or three coats of gum dammar 

 to finish it. 



Some insects, such as May-flies, &c., are, however, often 

 preserved by immersion in a solution of one part of chloride 

 of calcium in three or four parts of water ; but this has not 

 been recommended amongst the preservative liquids, as the 

 colour, which is often an attractive quality of this class of 

 objects, is thereby destroyed. 



We have now noticed the treatment which must be ap- 

 plied to those objects which are to be preserved in liquids 

 and cells. We may here state that all slides of this kind 

 should be examined at short intervals, as they will be found 

 now and then to require another coating of varnish round 

 the edge of the thin glass cover to prevent all dan'ger of 

 leakage. The use of the air-pump, in the first instance 

 (as before recommended), and this precaution as to the 

 varnish, will render the slides less liable to leakage and air- 

 bubbles, which so very frequently render them almost 

 worthless. 



