90 PREPARATION AND MOUNTING 
CHAPTHS ITV; 
MOUNTING IN CANADA BALSAM. 
Tue nature and use of this substance has been before spoken ° 
of, so that the method of working with it may be at once 
described. 
Perfect dryness of the objects is, if possible, more neces- 
sary in this mode of mounting than any other, as dampness 
remaining in the object will assuredly cause a cloudiness to 
‘ make its appearance in a short time after it is fixed. Where 
pressure does not injure the specimens, they are most suc- 
cessfully treated when first dried betwixt the leaves of a 
book, or in any other way which may prove most convenient, 
as noticed in Chapter IIT. 
Before describing the methods of proceeding with par- 
ticular objects, general rules may be given which should be 
observed in order to succeed in this branch of mounting. 
As the object is to be thoroughly immersed in the balsam, 
it is evident that when it has once been covered, so it must 
remain, unless we again free it by a process hereafter men- 
tioned, which is very troublesome; and on this account there 
must be nothing whatever in the balsam except the object. 
The inexperienced may think this an unnecessary caution ; 
but the greatest difficulty he will meet with is to get rid of 
minute bubbles of air, perhaps invisible to the naked eye, 
which appear like small globules when under the microscope, 
and render the slide unsightly, or even worthless. Balsam 
dissolved in benzole will be found invaluable in mounting 
without air-bubbles ; if a few are left in the specimen, by 
the next morning they will have entirely disappeared. In 
making this solution the balsam should be first boiled 
gently till on dropping a small quantity into water it is 
