TEEATMENT OF THE COMSTOCK OEES. 207 



shaft, which is placed directly in front of the batteries, and which receives its 

 motion from the driving power of the mill. The stamps move vertically 

 between guides that form a part of the battery frame. 



Fig. 1, on Plate XIX, shows a front elevation, and Fig. 2, a transverse 

 section, on the line A B of Fig. 1, of two five-stamp batteries, the several 

 parts of which are indicated by the table of reference accompanying the 

 drawing. 



The foundation for the batteries in stamp mills generally preferred in 

 Nevada, as well as in California, consists usually of heavy timbers, standing 

 vertically, placed close together, and firmly connected by means of cross tim- 

 bers and bolts of iron. The timbers are from 6 to 12 feet long, according to 

 the character of the ground and the desired height of discharge for the mor- 

 tar. Sometimes they stand on a horizontal timber, so laid as to serve as the 

 base of two or more batteries, and resting upon the ground, the surface of 

 which has previously been removed and leveled down sufficiently for the 

 whole number of batteries to be placed on a firm bottom. When the founda- 

 tion-timbers are in place, the space about them is packed and stamped as 

 firmly as possible with clay or earth. Where the ground on which the bat- 

 teries are to be built is a hard, compact gravel or a firm, clayey material, the 

 surface is sometimes leveled ofi" so as to admit of laying the transverse sill- 

 timbers, T, of the battery frame, and a narrow pit is then excavated, only 

 long and wide enough to receive the ends of the mortar-blocks, and several 

 feet deep, into which the posts or blocks are introduced, in a vertical position, 

 their bottom ends resting directly on the ground, witiiout any intervening 

 horizontal timber. The remaining space in the pit may then be compactly 

 filled with clay that is pounded or stamped firmly into its place. The sill- 

 timbers, T, and the battery posts, C, are securely bolted to the foundation- 

 timbers. The posts, C, are braced by the timbers, D, and the rods, R, and 

 are connected by the tie timbers, G, G', which also support the guides, g, g'. 



MoRTAES. — The mortars are now usually placed directly upon the verti- 

 cal mortar-blocks, without any horizontal piece intervening, and are secured 

 in their place by bolts shown in the figure. They may be constructed of 

 wood and iron, having a solid iron bed-plate, with sides and ends of wood, 

 forming the stamping trough ; or they may be made entirely of iron. In the 



