112 



DRESSING OF ORES 



the refuse of the inferior ores. It appears that these tailings were dressed by the 

 separators with more than triple the profit to the proprietors than that realised by 



688 



the ordinary methods. 



The body of the jigger, fig. 688, is con- 

 structed of wrought iron, the head-piece 

 of cast iron. The sieve bottom is clipped 

 between the head-piece and flange upon 

 which the latter rests. The driving gear 

 consists of a shaft, with fast and loose 

 riggers, and a cam. This cam passes 

 through the centre line of the piston- 

 rod, the latter being lifted by the former 

 against a spring composed of alternate 

 plates of iron and India-rubber, the throw 

 of the spring being rendered longer or 

 shorter by means of screws and nuts. 

 The valve for clearing the hutch is shown 

 between the piston and sieve compart- 

 ment. The sized sand when thrown 

 upon the sieve is jigged ; and on the com- 

 pletion of this operation, the skimming 

 of the worthless portion is effected by 

 hand. 



Triple Sieve Jigger. The three-sieve 

 jigger is sometimes used for effecting 

 a separation of lead and blende ore, 

 associated with carbonate of iron, or 

 heavy spar. The transverse section, Jig. 

 689, shows hutch a, piston b, bridge c, 

 regulating screw /, rocking shaft and 



gear q, and discharge launder k. The 



longitudinal section, fig. 690, exhibits 



three sieve plates k, three bridges I, each bridge enclosing an ore regulator, three 

 discharge valves in, ore pipes , furnished with stop valves o, ore trays p, fitted 

 with perforated bottoms ; and ore tray launders r. Sand suitably sized introduced at 

 s, passes under the slide t, when it is progressed across the perforated plate to the 

 first bridge ; the ore flows into the receptacle u, while sand and ore, carried over the 

 bridge, fall on the second sieve, and after treatment, pass to the third sieve. From 

 the second sieve, mixed ore is obtained, from the third, a s:nul sparingly mixed with 

 ore, and from the discharge shoot r, impoverished sand. The stuff lodged in the pipes 

 n, is from time to time drawn into trays fitted with perforated bottoms, or other- 

 wise, into boxes sot in the ground. The ore regulators are formed so as to allow of 

 the passage of largo or fine grains, and of the enrichment of rich or poor stuff. Three 

 or four of these jiggers may bo combined together, so as to treat the sand as it comes 

 from the trommels. Any necessary adjustment of stroke for jigging the stuff success- 

 fully is readily effected by shifting the cheek on the driving !'-\vr. Water may bo 

 supplied to the hutches, cither by a wrought-iron pipe, furnished with a stop-cock, or 

 by means of an ordinary launder. 



For jigging sand from two to ten millimeters in diameter, the pistons should make 

 from seventy to eighty strokes per minute. 



Hancock's Percussion Jigger. This continuous jigger, Ji<js. 691, 692, consists of a 

 V-shapod hutch contained within a frame, a suspended sieve, foot gear, side rods, and 



