OF MICROSCOPIC OBJECTS. 113 
rather difficult process, and will not, on that account, be de- 
scribed here; but when possessed, a small quantity of a 
strong solution in water must be made, and a little placed 
on the slide, and evaporated slowly. Part of the salt will 
then be deposited in circles with the needle-like crystals 
extending from common centres. They should then be 
mounted in pure Canada balsam ; and, when the best colours 
are wanted, used with the selenite plate. Of this class of 
erystal, salicine is a universal favourite, and can be easily 
procured of most chemists. The crystals may be produced 
in two ways :—A small portion of the salt must be placed 
upon the slide, and a strong heat applied underneath until 
fusion ensues ; the matter should then be evenly and thinly 
spread over the surface. Ina short time the crystals will 
form, and are generally larger than those procured by the 
following process; but the uncertainty is increased a little 
when fusion is used, which, however, is desirable with many 
salts. Secondly, make a saturated solution of salicine, 
which is effected by boiling one part of the salt in eighteen 
of water, and allowing it to cool. Place a little upon the 
slide, and let it evaporate spontaneously, or with the aid of 
gentle heat. The crystals are generally uniform, and with 
ordinary powers quite large enough to make a beautiful 
object. ‘'Cheir circular shape and gorgeous colours—even 
without a selenite plate—have made them such great 
favourites that there are few cabinets without them. 
There are also some salts which are crystallized in a some- 
what different manner from those before mentioned. San- 
tonime is one of the most beautiful, and will illustrate my 
meaning. Place a small portion upon a slide, and heat over 
a lamp until it is fused. With a hot needle spread the salt 
over the surface required. As the slide cools, the formation 
of crystals takes place, until it becomes one mass. ‘This 
salt is slightly soluble in the ordinary balsam, and should 
be mounted in castor oil. If, however, the slide is well 
covered under the thin giass, the balsam soon becomes 
saturated, and very little injury results. According to the 
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