1887.] MICROSCOPICAL JOURNAL. 99 
did not know its exact composition, but had been told that it contained shellac, copal, 
linseed oil, and turpentine. Itruns freely, makes smooth rings, dries readily and quickly, 
and is extremely adhesive. It is cleanly. Slides made with it had not changed in six 
months. It can be used also as a mounting medium.. It does not affect polarization. 
Water and glycerin mounts are very easily made. A cell can be made, a mount made, 
and cover-glass put on inside of ten minutes. Wet slides can be ringed by simply 
wiping off the superfluous moisture and running a ring around. This makes it easy 
to preserve urinary deposits which otherwise would be lost. Several slides were shown, 
some of which, mounted only about four hours before the meeting of the Society, were 
quite hard enough to bear ordinary handling. Dr. Taylor said :—I think this varnish 
contains oxidized linseed oil, which will account for its polish and rapid drying, I 
have used it with success, and think it almost as good as James’ and much cheaper. 
Almost any color can be mixed with it. 
Dr. Schaeffer said :—I think the cement contains asphalt. In my experience some 
balsam preparation answers better for a cement than anythingelse. Time is the only 
test for a cement. 
Dr. Reyburn said :—Some years ago I used as a varnish a fine article of copal with 
success. The principal objection to it was its slowness in drying. 
Prof. Seaman said :—I think the cement a valuable addition to our armamentarium. 
I do not think there is much oxidized oil, because it is so cheap, and the oxidized oil 
is costly. Thecheapest gums in the market are kaurianddamar. I think the cement 
contains kauri and the silicates of soda and potash combined with turpentine and ben- 
zine. Nearly all cements have been failures because of their lack of adhesiveness to glass. 
The annual soirée of this Society will be held on April 26th. 
E. A. BALLocH, Rec. Secr. 
a 
WASHINGTON, D. C. 
At the 59th regular meeting, April 12th, 1887, Mr. F. T. Chapman said :— 
Artificially prepared silver crystals make fine opaque objects for the microscope, 
either as permanent mounts, or for observing the process of crystallization, and they 
may be readily prepared, although some care is necessary in order to obtain the best 
results, especially if the preparation is designed to be permanent. 
The deposition of silver from a solution of silver nitrate by means of copper, prefer- 
ably a copper-wire ring placed in a sufficiently deep cement cell, gives very good 
results if the wire ring and the thicker mass of crystals at the edge be removed, and 
the specimen then thoroughly dried and protected by a cover-glass in the usual way. 
Much better results, however, can be obtained with a brass cell provided with a 
removable cover or cap (known as the ‘Pierce cell’), and cemented to a glass slip, 
the cell being backed by dark-colored wax. 
When filled with the solution, the deposition of silver crystals on the inner surface 
of the cell will immediately commence and proceed slowly toward, but should not be 
permitted to reach, the centre. When the crystals have approached so near the centre 
as to leave a clear space of about one-eighth of an inch in diameter, the solution should 
be removed by means of a small piece of blotting paper placed on top of the cell and 
allowed to remain for a moment. 
The strength of the solution is not important, but should not be very weak, as the 
feathery masses of cyrstals that add greatly to the beauty and ‘depth’ of the mount 
do not then appper. 
If the crystals, when forming, appear white and brilliant, or darken slightly, or 
appear to be very fine or small at the sides of the cell, while those at the bottom are 
spray-like and quite large, the result will usually be successful, although the best con- 
ditions are when the bottom of the cell is occupied by several large feathery sprays of 
crystals, and the sides by shorter sprays or spine-like crystals, the whole being white 
and brilliant. 
Sometimes, after the solution has been removed, a deposition of copper on the silver 
will be found, or crystals of copper salts will intermingle with the silver, and mar its 
appearance, in which case it is necessary to reprepare the mount. 
If the silver be permitted to reach the centre, a black precipitate will form and spoil 
the preparation as a permanent mount, but as the fluid is then filled with a mass of 
minute, sparkling crystals in constant motion, the effect is both interesting and beau- 
tiful when viewed with a power of about twenty-five or fifty diameters. 
The time usually occupied in preparing a silver mount is about five minutes, the 
