DRESSING OF ORES 



115 



with the cam wheel ; g, rod for regulating length of stroke and lifting side levers when 

 necessary above the periphery of the cam wheel ; h, driving rigger ; i, radius bar for 

 throwing the sieve horizontally ; j, sliding block for lengthening or shortening the 

 throw of the sieve ; k t columns for carrying the hutch ; I, waste compartment ; m, 

 valve for passage of water and castaways ; n, ore compartments ; p, pipe 2 inches dia- 

 meter, one to each compartment for discharging the latter. The dimensions of the 

 sieve are as follow: width 32 inches, depth 6 inches, length 20 feet. The sieve 

 for dressing 1 to 3 millimeter stuff, has holes for the first 6 feet, 4 millimeters 

 square ; then, holes 3 millimeters square, until within 6 iuches of the end, when 

 it has holes 6 millimeters square. The wire bottom has a fall of f of an inch in the 

 total length. The ragging bars are 2 inches deep, and are supported by a f of an 

 inch square bar of iron. 



The stuff is introduced to the hutch by a 3-inch pipe, and is jigged from the head to 

 the foot of the sieve, the ore falling between the ragging bars and thence into the 

 V-shaped receptacles. The speed of sieve is 150 strokes per minute. The passage of 

 water between the sieve frame and hutch is in a great measure prevented, as in Hugo 

 Preuss's machine, by nailing on the bottom edge of the sieve frame a strip of 

 leather about three inches deep. The total length of hutch is 22 feet. In Preuss's 

 machine referred to and which was erected at Przibram in 1866, 3 sieves were employed, 

 each slightly stepped one below the other ; these were worked by means of shifting 

 excentrics, and without any radius bars to effect a forward throw. At the Moonta 

 Mines, South Australia, under the able direction of Mr. Hancock, the percussion 

 jigger is found to despatch a large quantity of stuff in a given period. The ore consists 

 of rich carbonates, sulphide of copper, and copper pyrites associated with a free light 

 vein-stone. 



692 



The jigger shown in fig. 693, is suitable for enriching coarse sand, that is, stuff 

 composed of coarse grains from 2 to 7 millimeters diameter. In the longitudinal 

 section, a a a the sieves are set so as to drop 1 inch in 36 ; b, grids supporting sieves ; 

 c, wrought-iron cylinders for regulating the outflow of ore and orey stuff; d t discharge 

 pipes ; e, regulators attached to pipes by means of set screws ; /, ore boxes ; g, piston- 

 rods, two to each piston ; h, driving lever ; j, launder for admitting stuff to jigger ; Jc, 

 shoot for getting rid of castaways. In the transverse section g is the piston ; m, 

 launder for supplying water to piston boxes ; n, draw-off plug ; y, ore boxes. 



The width of sieve may vary from 20 to 30 inches, and the length increased to such 

 extent as may be found desirable. 



UtscKs Patent Jigger. This machine, introduced by Messrs. Kember and Co. of 

 London, is so constructed that the grains or particles of the material with which 

 it is supplied are properly balanced, and subjected to an unvarying pressure, 

 whilst a continuous self-acting delivery of the minerals is obtained. Fig. 694 is 

 a longitudinal vertical section of the apparatus, and fig. 695 is a transverse 

 section, a, supply launder; b. jigging compartment; c, d, and e, separating com- 



i 2 



