108 



DRESSING OF ORES 



the arrangement F, o, H, suspended at i, and having at the extremity H a box for 

 the reception of small stones, to be used for the purpose of counterpoising the weight 



of the sieve and several fittings. By 

 moving the rod F, sliding in x, the 

 workman gives the required motion to 

 the sieve, and when its contents have 

 boon sufficiently washed, ho removes 

 them by the same means as when 

 the hand sieve is employed. 



Hand Jigging or Vrake Sieve. The 

 brake sieve, jig. 683, is of rectangular 

 shape as well as the cistern in which 

 it is agitated. A, wooden lever, hav- 

 ing its axis at F ; B, piece of wrought- 

 iron bolted to the end of lever A, 

 whilst its upper end passes freely 

 through a slot opening in lever D, and 

 having two shoulder projections c ; E, 

 axis of lover D; G, bars connected with 

 lever D, supported on axle E, and from 

 which the iron rods H H depend ; j, rect- 

 angular sieve ; K, within the hutch ; L, 

 shoot for overflow of water ; M, recep- 

 tacle for retaining any fine ore which 

 may escape with the water from L, 

 as well as for receiving the hutch- 

 work. A boy placed near the end of 

 - .i lever A, by the action of leaping, jerks 

 & it smartly up and down, so as to shake 

 effectually the sieve j. Each jolt not 

 only makes the fine part pass through the meshes, but changes the relative position 

 of those, which remain in the sieve, bringing the purer and heavier pieces even- 



tually to the bottom. The mingled fragments of ore and stony substances lie above 

 them, while the poor and light pieces arc at the top: those are first scraped off 

 by the limp, then the mixed portion, and lastly the ore, which is usually carried to 

 the ore heap. The sieve frame maybe made 2x4 feet inside, and 8 to 9 inches deep. 

 The hutch should then bo 5 feet long, 3 feet wide and 4i feet deep, constructed of 

 good deal boards 2 inches thick. The quantity of stuff which a boy can jig in ton 

 hours will depend upon several circumstances. With a sieve six holes to the square 

 inch and a tolerably light waste, from five to six tons can bo operated on. 



Machine Jigging. The machine jigger, represented in jig. 684, is constructed on 

 the same principle as the h;in<l apparatus. The hutches arc, however, somewhat 

 larger, being 6 feet long, 4 foot wide, and 4 foot deep. A, fly-wheel ; u, driving wheel ; 

 C, cog wheel receiving motion from B, and giving motion to a crank from which 

 depends a rod attached to a lever D. The vertical rod E passes through a slot 

 opening in the wooden lever F, and by these several combinations a vertical moTomcnt 

 and jerk is given to the sieve contained in the cistern o. 



"\Vhep it is required to discharge the sieve, the lever H is depressed, and the pin 



