THE MICROSCOPE. 209 
Second—Spin two rings of the transparent gum cement around 
the edge of the cover, and give at least twenty-four hours’ time to 
harden before applying the second coat. 
Third—Apply as many coats of these white or colored cements 
as you like, but don’t drown the mount with the first coat. Apply 
thin coats. 
Fourth—Give at least twenty-four or thirty hours’ time for 
each coat to harden. 
Fifth—Ornament, if you wish, and in due time brush off the 
dust and give it a thin coat of a good finishing varnish, and give 
plenty of time to dry and harden before applying a second or third 
coat. I find Winsor & Newton’s mastic picture-varnish to make the 
finest finish and is stronger and more durable than damar or 
shellac varnish, and is nearly colorless. I have not yet tried the — 
new copal varnish. The enamel cement on page 95, Dr. James’ 
Elementary Microscopical Technology, may be a good finishing 
varnish, and just the article for the body of the ring around the 
mounts of Farrant’s medium, glycerin jelly, etc. A beautiful white 
cement for the mounts last mentioned is as follows: Add sufficient 
Cremnitz-white to mastic, or any good colorless varnish, or Brown’s 
rubber cement, to give the required opacity, and mix them 
thoroughly. The white might be tried with Dr. James’ enamel. 
This white cement is much stronger than white zinc, and does 
not assume the brick-red and dirty appearance so often noticed 
on white-zine slides. I only use this white cement as a varnish to 
finish mounts; but never use it on balsam or resinous mounts, as it 
is liable to run in like white zinc. I have discarded white-zinc 
cement entirely as a nuisance. The best of it is too brittle in the 
start, and sooner or later crumbles or scales off. I don’t trust 
glycerin as a mounting medium, as it is nearly impossible to keep it 
in a cell; furthermore, I have my doubts whether glycerin C. P. can 
be prepared to resist the action of germs on certain specimens with- 
out injuring or altering the form and appearance instead of pre- 
serving them, e. g., biological or pathological specimens. 
I am testing two kinds of media (my own preparation): Phosa- 
nalin, No. 2, 3, 4, 5 and 6, all soluble in any oily solvent, except 
No. 4; all to be a substitute for the balsams in general use without 
their objections—turning yellow and red, or a dirty appearance, 
brittleness, semi-opaque, crystalizing, crushing and distorting the 
cells of specimens in severe shrinkage, precipitations, lack of 
tenacity, ete. 
The other medium: Hydro-crystal, No. 2, 3, 4, 5, 6 and 7, all 
