20 HEYS, ON MOUNTING MICROSCOPICAL PREPARATIONS. 
yellow tinge which is observable in most samples when first 
mixed. Another very important point is, that it sets much 
quicker than if only mixed as wanted, and there is very little 
waste. Air bubbles also escape more rapidly. I do not 
use heat either to the balsam or the glass slide, nor, in fact, 
in any part of the process. My custom is to save up a 
number of objects for mounting, and then put up a quantity 
at any favorable opportunity. Those which have been im- 
mersed for some time in turpentine need only to be rinsed 
in a little perfectly clean turpentine, placed in a proper position 
on the glass slide, a sufficient quantity of balsam dropped 
from the lip of the half-ounce bottle, and then, by the aid of a 
pair of forceps, the cover laid gently over without delay. 
Except in rare cases, the cover should not be put under pres- 
sure after being once laid on, as many objects are liable to 
be distorted by pressure whilst the balsam is setting. As 
soon as a number of slides have been finished they may be 
labelled and arranged (flat of course) in the cabinet, and will 
require no further attention. In a few days, or at most, a 
week, the slides may be safely used with care, and in the 
course of a fortnight the balsam will be firmly set. (Should 
specimens be wanted very quickly, the drying may be has- 
tened by placing the slides on a warm shelf in a hot kitchen, 
or any similar place.) Such objects as the pollen of flowers, 
the thece of ferns, spores of mosses, and some seeds, only 
require to be dry to be mounted with perfect safety. Should 
they contain moisture, the preparation will probably become 
milky and clouded. In consequence of the extraordinary 
facility with which the fluid penetrates every portion of a 
specimen the air-pump is not needed; for if the object is 
surrounded with bubbles on all sides at the time of mounting, 
yet on examination, after a day or two, it will be discovered 
that the bubbles have all disappeared, and the specimen will 
be so beautifully transparent that it will appear to be set in 
plate glass. There is another advantage in having a stock of 
prepared balsam at hand :—Should you wish to mount only 
one or two slides no troublesome preparation is needed, nor is 
there the least waste of time or material; for you have only 
to adjust your object on the slide, pour on a drop or two of 
the balsam, put on the cover, and the work is ended. Those 
microscopists who have mounted objects in Canada balsam 
upon the old plan will well remember how troublesome it 
was, and the great care required to have the balsam, slide, 
and cover, all of the right temperature. ‘They will remember 
also how often, owing to the complicated nature of the 
operation, the specimen was either spoilt or imperfectly dis- 
