THE GEELONG NATURALIST. 15 
their external surface by reflected or condensed light, and covering 
with thin glass to exclude the dust. But those objects which it is 
intended to examine by transmitted light, require in most cases, to 
be prepared previously to mounting them in. whatever vehicle may 
be found best for exhibiting their structure. What I use most for 
mounting transparent objects is Canada balsam; the pure balsam is 
too thick for use, but it is easily diluted with spirits of turpentine 
‘so as to render it sufficiently fluid to permeate the structure to be 
exhibited. As a general rule it should be thin enough to drop 
readily from the point of a needle. 
There are some objects whose structure is so transparent that 
they must be mounted dry; e.g., scales from the wings of moths and 
butterflies. All that is necessary in preparing objects for dry 
mounting is to take care that they are free from extraneous matter, 
and to fix them permanently in the position which will show them 
to the best advantage. Care must be taken that thereis no draught 
of air through the room while handling delicate objects; many a 
beautiful specimen I have lost by its being wafted from under m 
hand, even by my own breath. In mounting entomologieal speci- 
mens, the first thing, of course, is the dissection of the insect. The 
parts to be prepared and mounted should first be carefully 
‘detached from the insect, then put into a solution of liquid potassae 
for a few days to soften and dissolve out the fat and soft parts. 
The length of time to be kept must be found out from experience, 
‘but as & general rule the object assumes a certain amount of clear- 
ness when it has been long enough in the potassae. 
When this is the case the object must be put into a flat 
, receptacle and put in soak for two or three hours in soft or distilled 
water. It may then be put between two slips of glass and gently 
pressed till the softer parts are removed. These: will frequently 
adhere to the edge of the object but can be washed off in water by 
the aid of a camel-hair brush. Place the object now and then 
under the microscope to see that all the extraneous matter is 
removed. When this is so, take the specimen up carefully with the 
camel-hair brush and lay it on a piece of glass; arrange it to its 
natural appearance with the brush and a fine pointed needle; place 
a second piece of glass over it and press it flat between the two slips of 
glass, and compress it by clips. 
When dry, which will be in about twenty-four hours, the object 
may be detached and should at once be put into spirits of turpentine 
for a few days till it is fit for mounting. Some objects take longer 
