100 



DRESSING OF ORES 



676 



are two chests, out of which tho oro to bo ground falls spontaneously into tho two 

 troughs of the stamps. Of late years, however, the ore is mostly supplied by hand ; 



the watercourse terminates a short distance above 

 the middle of the wheel b. There is a stream of 

 water for the service of the stamps, and laun- 

 ders proceeding from it, to lead tho water into 

 the two stamp troughs ; the launder of discharge 

 is common to tho two batteries or sets of stamps 

 through which the water carries off the sand 

 or stamped ore. There is a moveablo tablo of 

 separation, mounted with two sieves. The sands 

 pass immediately into the launder placed upon a 

 level with the floor, and separated into two com- 

 partments, the first of which empties its water 

 into the second. There are two boards of sepa- 

 ration, or tables, laid upon the ground, with a 

 very slight slope of only 16 inches from their top 

 to their bottom. Each of these boards is divided 

 into four cases with edges ; the whole being ar- 

 ranged so that it is possible, by means of a 

 flood-gate or sluice, to cause the superfluous 

 water of the case to pass into the following 

 ones. Thus the work can go on without inter- 

 ruption, and alternately upon the two boards. 

 There are winding canals in the labyrinth, N, N, N, 

 in which are deposited the particles carried 

 along by the water which has passed upon the 

 boards. The depth of these canals gradually 

 increases from 12 to 20 inches, to give a suitable 

 descent for maintaining the water-flow. A,t D 

 two percussion tables aro placed. F, o, are two 

 German chests. H, j, are two percussion tables, 

 which are driven by the cams z z, fixed upon 

 the main shaft x y. K.' K" are two sloping sweep 

 tables (a balai}. The German chests are rectan- 

 gular, being about 3 yards long, \ a yard broad, 

 with sides 18 inches high ; and their inclination 

 is such that the lower end is about 15 inches 

 beneath the level of tho upper. At their upper 

 end, usually called the bolster, a kind of trough 

 or box, without any edge at tho side next the 

 chest, is placed containing the ore to bo washed. 

 Tho water is allowed to fall upon the bolster in 

 a thin sheet. The sleeping tables have upright 

 edges ; they are from 4 to 5 yards long, nearly 

 2 yards wide, and have fully a yard of inclina- 

 tion. The tables aro sometimes covered with cloth, particularly in treating ores that 

 contain gold, on a supposition that the woollen or linen fibres would better retain tho 

 metallic particles: but this method appears on trial to merit no confidence, for it 

 produces a very impure Scklich. 



Califomian and Nevada Stamps. The foundation is generally formed of vertical 

 timbers, set close together, and firmly braced by means of cross timbers and bolts. 

 Each piece of timber, 2 feet by 18 inches, is from 6 to 12 feet long, according to tho 

 nature of tho ground, and height of tho discharging grato. When the timbers are in 

 position, tho adjacent earth is firmly rammed together, and tho foundation thoroughly 

 consolidated. The sill, vertical, and diagonal timbers aro strongly connected and later- 

 ally braced so as to render movement all but impossible. Tho stamps box is placed 

 directly upon the vertical timber foundation, and is secured by bolts. Tho length of 

 box shown in Jig. 677, is 4 feet 6 inches, depth 4 feet, inside width 12 inches ; and is 

 so cast that bottom, sides, and ends, aro in one piece. The feed opening is an aperture 

 4 inches wide and 3 feet 9 inches long. Tho discharge or grato opening is 46 inches long 

 and 10 inches deep, tho bottom edge being 4 inches above the top of the die. Tho 

 grato is attached to a frame, secured l.y wedges in /grooves cast in each end of the box, 

 and by two lugs in front of tho discharge opening. It is usually inclined at about 7 

 with tho view of facilitating tho discharge of tho stuff. For wot stamping, Russian sheet 

 iron is employed, having holes varying from one half to ono millimeter in diameter. 

 The grate is attached to tho frame by means of screws and to confine tho 'flash' of 



