318 Gold in Califorma. [July, 
necessarily connected with the solvent by which the precious metal 
was held in solution. In the present state of our knowledge of this 
subject, it would be impossible fo explain the exact process by which 
the solution of gold was effected. It has, however, been shown by 
Wurtz, that finely divided gold is soluble in sesquichloride of iron, 
and, more sparingly, in the sesquisulphate of that metal. It is also 
well known that iron pyrites, sometimes at least, result from the 
action of redrcing agents on the sulphates of that metal. If there- 
fore a sulphate of iron, in a solution containing gold, should become 
transformed by the action of a reducing agent mto pyrites, the gold, 
at the same time, being reduced to the metallic state, would proba- 
bly be found enclosed in the resulting crystals of that mineral. 
On being brought to the surface the auriferous rock is first 
passed through a Blake’s crusher, or is broken into fragments of a 
suitable weight, by the use of heavy hammers, and then reduced to 
the state of a very fine sand, under the pestles of a stamping mill. 
This machine differs from that employed in Cornwall for the treat- 
ment of tin ores, in so much as the heads and lifters, or “stems,” 
are both invariably of iron, and of a cylindrical form, whilst the 
cams are arranged around a heavy wrought-iron shaft im such a 
way as to cause them to be raised in regular succession, giving to 
each, at the same time, a rotary motion. The “ battery boxes,” or 
“cofers,” are also formed of a single iron casting, and movable “dies” 
are so placed along its bottom as to correspond with the “shoes” 
which form the wearing surfaces of the pestles. These shoes and 
dies possess the advantage of being readily changed when worn 
out, and the motion of rotation before referred to has the effect 
of keeping the faces constantly even. These machines, which in- 
stead of being driven by toothed gearing are worked by means of 
broad indiarubber belts, are fed by a shovel through a long slot at 
the back of each battery box. 
In some cases a little quicksilver is, at regular intervals, dropped 
into the battery, but in others no mercury is used under the pestles, 
and the pulverized rock is simply washed by a stream of water, 
which is admitted into the arrangement by ordinary gas-pipes, 
through fine gratings in front of each cofer, and over a series of 
blankets covering the inside surfaces of wooden troughs inclined 
at a slight angle with the horizon. 
These blankets are frequently removed for the purpose of being 
washed in large tanks, in which the auriferous matter accumulates, 
and from whence it is subsequently removed to be passed through 
an amalgamator. In order that there should be no interruption 
in the continuous action of the machinery, two of these blanket- 
troughs are laid down before each battery, so that when the blankets 
from one of them are being washed, the stream of water and sand 
issuing from the mill is conducted over the other. 
