30 A. H. Chester—Artificial Crystals of Gold. 
electro-gilding, but to deposit it in the crystalline form is a 
process of comparatively recent date, having been patented in 
1860, as a method of sears gold for dental purposes. The 
process is briefly as follows. A solution of chloride of gold 
and ammonium is placed in a shallow dish coated with heavy 
gold foil, which is connected with the zinc plate of a large 
Daniells’ ‘battery. Near 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 is controlled by a coil of 
wire arranged as a rheostat, a clamp terminating one of the 
battery wires enabling the operator to include a greater or less 
number of coils in the circuit. The necessary conditions being 
fulfilled, on completing the circuit the gold is gradually dis- 
solved from the roll and deposited on the bottom of the dish 
in bright crystalline Sm having the appearance of eure or 
fern leaves when examined under the microscope. 
shows one of these crystals magnified one hasten 
and fifty diameters. At first sight this appears to be 
like certain natural crystals occasionally found, and 
the arborescent forms of other isometric minerals. 
But all such crystals that I have seen have invariably 
the angle of 60° between the side ribs and the midrib, 
making an angle of 120° between the two sets of ribs. 
Gold, silver and copper all show this characteristic, 
which is particularly illustrated in the crystals 
descri by Professor Vom Rath in the last volume 
of Groth’s Zeitschrift fiir Krystallographie. It is 
uite difficult in the case of these artificial crystals to 
measure their angles, because the midrib is usually more or less 
curved, and the whole form presents great irregularities. 
4 can coh be done ne ae for a single 
on one side is 41° and on ‘see other 79°. The 
average of fifty measurements of these crys- 
taken at random is on one side 44° 38’ 
and on the other 75° 47’. Nineteen measurements made at 
another time made the two angles 42° 18’ and 78° 24’. The 
