GOLD Mim:fTG IS COLORADO. 549 



found in Colorado. The mortar in common use in tins Territory is a simple 

 iron trough, four or five feet long, twelve or fourteen inches wide, and nine 

 inches deep, cast with a solid bottom, which should be nine or ten inches 

 thick, but is often less. It is laid on wooden foundations, made, sometimes, 

 like those already described, of sound timbers, set vertically, their ends rest- 

 ing on firm ground ; or, more commonly, on a long, horizontal mortar-block, 

 that rests on other cross-timbers, placed horizontally. The bottom of the mor- 

 tar on the inside contains recesses into which the dies sink and are secured. 

 The latter usually have flat octagonal bases with a wearing surface rising 

 above it of cylindrical form, corresponding to that of the shoe, usually 8 

 inches in diameter. (See Fig. 1, Plate XX.) The battery-work above the 

 mortar is all of wood. The housings are of plank, the front and back being 

 so made as to be readily taken down, giving access to the inside of the bat- 

 tery. The screens are of Russia sheet-iron, 9 or 10 inches wide and as long 

 as the battery, fixed in a frame that can be secured in front of the bat- 

 tery by keys fitting in the grooves, or other simple contrivances, one of which 

 is shown in the drawing. The discharge is usually only in front. The 

 screens are punched with very fine shts about one-third of an inch long and 

 the same distance apart. The battery usually contains four or five stamps. 

 These in general features resemble the California stamps, consisting 

 of a stem, head, shoe, and tappet or collar, by means of which the cam 

 raises the stamp. The tappet in Colorado is usually adjusted to its place on 

 the stem by turning it on a screw-thread, cut for the purpose, and is fixed by 

 means of a key or wedge that is driven into a key-seat cut in the tappet and 

 stem. In some mills the stamp-stems are made with a slight taper in the part 

 to which the tappet is to be attached, and the latter, having a corresponding 

 form, being driven on to the stem, holds its place by friction. Such is the 

 form of the tappet shown in the drawing on Plate XXXIII. The California 

 tappet, described in a foregoing chapter, and illustrated in Fig. 4, Plate XX, 

 which is deemed by those mill-men who have used it as superior to any other, 

 has not yet come into general use in Colorado. 



The stamp mills of Gilpin County are generally operated by steam, though 

 some that are favorably situated on the water-courses obtain power from that 

 source. Many mills, however, are located on the mine supplying the ore, the 



