826 General Notes. | November, 
inventor or from the dealers in microscopical supplies. The cut 
gives a sectional view of this cell, the dotted line 
indicating the cover glass and the open space below it the loca- 
tion of the object. The glass cover is easily attached by a little 
shellac or other suitable cement; and the whole cell may be 
cemented, if desired, to the center of a common glass slide. For 
convenience of exchanging by post, or for storing a large num- 
ber of objects for future reference, in a small space, the glass 
slide may sometimes be omitted altogether, the name or number 
indicating the object being merely attached to the back of the 
cell. 
ARTIFICIAL CRYSTALS oF GoLp.—In casting bars of pure gold 
for the manufacture of foil, traces of crystallization may often be 
observed upon their upper surfaces, and sometimes distinct crys- 
talline forms. These are generally simple triangular faces slightly 
raised, very similar in appearance to specimens sometimes found 
in nature. Occasionally several faces of the octohedron may be 
. seen, the edge in some instances being half an inch in length, 
and quite sharp and well defined. The purer the gold is, the 
more likely the crystals are to form, and they are oftenest seen 
when the bars are cast from that which has been previously crys- 
tallized by the battery process described below. * * * 
he precipitation of gold from solution by the aid of a battery 
is a well-known process in the common operation of electro- 
gilding, but to deposit it in the crystalline form is a process of 
comparatively recent date, having been patented in 1860 asa 
method of preparing gold for dental purposes. The process 1S 
briefly as follows: A solution of chloride of gold and ammonium 
is placed in a shallow dish coated with heavy gold foil, which 1s 
connected with the zinc plate of a large Daniels’ battery. ear 
the top of the solution and connected with the copper plate of the 
battery, a roll made up of thin strips of pure gold is suspended, 
enclosed in a muslin bag. The strength of the battery current 1S 
controlled by a coil of wire arranged as a rheostat, a clamp ter- 
minating one of the battery wires enabling the operator to 1n- 
clude a greater or less number of coils in the circuit. The neces- 
sary conditions being fulfilled, on completing the circuit the gold 
is gradually dissolved from the roll and deposited on the bottom 
of the dish in bright crystalline flakes having the appearance or 
feathers or fern leaves when examined under the microscope. 
have been quite surprised that no trace of faces 1S to 
be observed upon these crystals, as is always the case with natural 
ones. The latter are seen under a low power to be made up oF 
show a slightly beaded look along the side ribs, but nothing that 
can be considered distinct crystalline forms, With the power- 
