1880. | Microscopy. 147 
occurred to me to attempt to preserve them in their own mother 
liquor. To do this paint on a slide a thin ring of gold size, whose 
entire diameter shall equal that of the cover glass. To make the 
edges of the ring smooth and true hold the flat edge of a small 
chisel against them at the points indicated by the straight lines in 
the figure, whirling the turn-table in the direction 
indicated by the arrow. As soon as the ring is 
finished heat it over the flame of a lamp until it 
becomes brown. Put into a test tube a little 
salycine, tartaric acid, prussiate of potash, or 
other substance adapted for examination with the 
polariscope, add water and apply heat until the 
solution is of such strength that crystals will form in it only when 
quite cold. Coat the ring, already hardened, with a little fresh 
size, and likewise the edge of the cover glass. Put the slide and 
cover glass thus prepared, on the hot plate for a few minutes and 
then pour a few drops of the boiling solution from the test tube 
into the cell and apply the cover glass, immediately pressing it 
down gently with a dry cloth which will absorb the superfluous 
iquid. Touch the edge of the cover glass with gold size and 
then transfer to the turn-table and finish. If the above directions 
have been followed correctly the cell will contain a clear liquid 
which begins to deposit crystals as it cools. Transfer the slide to 
the stage of the microscope soon enough to watch this process. 
Without the aid of the polariscope it is of interest, but with that 
accessory the spectacle presented is exceedingly beautiful. 
After standing for some time however, the crystals appear to 
lose their sharpness and perfection of form. They may be re- 
stored by a fresh application of heat sufficient to cause them to dis- 
Solve and enter upon new forms of combination. As a means of 
observing the process of crystallization this method appears to be 
the best, and many of the results as respects brilliancy of color 
and perfection of outline are unsurpassed. I would recommend 
however, that those who have not tried it, should make a moder- 
ately strong solution of salycine or tartaric acid in boiling water 
and pour it over a warmed slide, draining off the greater part im- _ r 
mediately. When crystallization ceases put a drop of Canada 
balsam in the center of the slide and apply a cover glass.. Exam- 
ine, and if found satisfactory, harden the balsam and finish in the x 
usual way. Having once learned these processes, there is no : 
limit to the range of experiments that may be made. For in- 
stance, a strong solution of santonine in chloroform gives very — 
fine crystals which are quite permanent and brilliant when mount- 
ed dry. It should be noted that the quantity and strength of the noe 
Solution employed will modify the results obtained, also agitation — Lg 
of the fluid whilst evaporating will in some instances introduce 
Crystals of an entirely different form from those obtained when 
'S permitted to remain undisturbed.—M. A. Verder. _ 
