550 MINmG INDUSTEY. 



stamping machinery being under the same roof with the hoisting or pumping 

 works and operated by the same power, which, where practicable, affords a 

 great saving in cost and care of machinery and in the labor of handling the 

 rock. The power is generally transmitted from the engine by belt to a coun- 

 ter-shaft, from which the stamps are usually run by gearing. The convenient 

 method, in use in Nevada and California, of running each battery or two bat- 

 teries by a belt, so that by applying or withdrawing a tightener any battery may 

 be set in motion or stopped independently of the other batteries, is not here in 

 use. A cam-shaft in Colorado is generally made long enough for all the stamps 

 in the mill, or if the mill be a large one, for twenty or more stamps, the stop- 

 page of one battery involving the delay of all the others run by the same 

 shaft. The cam-shaft is generally driven by a geared wheel, though the shaft 

 carrying the driving pinion is commonly operated by belting. 



Wet-crushing is used altogether in the milling of gold ores in Colorado. 

 Water is introduced into each battery by a number of small pipes that draw 

 their supply from a trough w, shown in the drawing. The quantity must be 

 sufficient to carry out the material as soon as it is reduced to the necessary 

 degree of fineness, this being determined by the mesh of the screen in front 

 of the battery through which it is discharged. Amalgamation is performed in 

 the battery, in which a supply of quicksilver is maintained for the pui-pose of 

 taking up the gold as soon as liberated by the crushing process. The quick- 

 silver is usually introduced into the batteries in small quantities from time to 

 time, as may be necessary, according to the richness of the ore and the 

 rapidity with which the amalgam is formed. The appearance of the latter, 

 as it issues from the battery, is one indication, to the attendant, of the quan- 

 tity of quicksilver present. Hard, dry, and dense particles of amalgam show 

 the lack of a sufficient quantity, while from the degree of fluidity of the par- 

 ticles the presence of a sufficient quantity, or of a surplus, of quicksilver may 

 be inferred. The ends of the batteries are lined with amalgamated copper- 

 plates, while another plate of the same kind, about 10 or 12 inches wide and 

 as long as the inside of the battery, is so fixed in a frame that it may be 

 introduced and secured in an inclined position behind the stamps. A similar 

 plate, though narrower, is generally used on the front or discharge side of the 

 battery. A portion of the amalgam, as it is formed in the battery and 



