138 PREPARATION 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 danger 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. 
