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, weighing from a hundred to a 

 thousand pounds. The wooden shaft has a mortice in front 

 near the top, and a cam on a revolving horizontal shaft enters 

 this mortice at every revolution. Vv'hen the cam slips out of 

 tlie 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 pulverization comes the separa- 

 tion of the gold from the rocky portion of the powder. The 

 means of separation are mechanical or chemical. The chemical 

 process is amalgamation ; the mechanical are those wherein the 

 gold is caught on a rough suriace with the aid of its specific 

 gravity. The chief reliance is upon amalgamation, and in some 

 large quartz-mills mechanical apj:)liances are not used at all for 

 catching the particles of gold, but only for catching amalgam. 



