MINING. 281 
the square and rotary. The square stamp has a perpendicular 
wooden shaft, six or eight feet long, and six or eight inches 
square, with an iron shoe, weighiig from a hundred to a 
thousand pounds. The wooden shaft has a mortice in front 
uear the top, and a cam on a revolving horizontal shaft enters 
this mortice at every revolution. When the cam slips out of 
the mortice, the stamp falls with all its weight upon the 
quartz in the “battery” or “‘stamping-box.” The rotary 
stamp has a shaft of wrought iron about two inches in diam- 
eter, and just before falling this shaft receives a whirling mo- 
tion, which is continued by the shoe as it strikes the quartz. 
The rotary stamp is considered superior to the square, its ad- 
vantage being that it crushes more rock with the same power, 
that it crushes more within the same space, and that it wears 
away less of the shoe in proportion to the amount of rock 
crushed. There are usually half a dozen square stamps or 
more, standing side by side in a square-stamp mill, and these 
do not all fall at the same moment, but successively, running 
from the head to the foot of the “ battery.” The quartz is put 
in at the head of the battery and is gradually driven to the 
foot. The rotary stamps sometimes stand side by side, and 
sometimes in a circle. The battery of both rotary and square 
stamps is surrounded by wire gauze, or a perforated iron 
plate, allowing the finely pulverized quartz to escape, and re- 
taining the coarser particles. Quartz is crushed wet and dry. 
In wet crushing a little stream of water runs into the battery 
on one side, and escapes on the other, carrying all the fine 
quartz with it. 
§ 211. Separation.—After pulverjzation comes the separa- 
tion of the gold from the rocky portion of the powder. The 
means of separation are mechanical or chemical. The cheinical 
process is amalgamation ; the mechanical are those wherein the 
gold is caught on a rough surface with the aid of its specific 
gravity. The chief reliance is upon amalgamation, and in some 
large quartz-mills mechanical appliances are not used at all for 
catching the particles of gold, but only for catching amalgam. 
13* ; 
