DRESSING OF ORES 



119 



A sheet of horse-hair forming the sieve is placed between two sheets of wire op 

 perforated places, having about eight holes to the lineal inch. The length of sieve is 

 30 inches : total length for 3 sieves, 7 feet, C inches ; width of sieve, 12 inches. The 

 depth from top of hutch to first sieve is (H inches; second sieve, Scinches; third 

 sieve, lOi- inches; width of receiving chamber between the sieves, 2 inches. Each 

 chamber "is discharged at the side through a plug-bole into boxes set in the ground. 

 The height of discharge openings into the several receptacles is about j 3 g ths of an inch, 

 height of transverse plates above sieve bottom, f", f", and of an inch. The pistons 

 make from 120 to 250 strokes per minute, according to the nature and fineness of the 

 stuff treated. The quantity of water required per minute is from 1 to 3 gallons per 

 sieve. 



Collom's Jigger. The peculiar features of this jigger are its tappet piston gear, and 

 the arrangement for discharging such grains of ragging as are too large to pass 

 through the bed, and too heavy to flow from one sieve to another. The construction, 

 as well as the mode of working the jigger, will be clearly understood from the following 

 remarks : 



1. These machines should be firmly set upon a frame of square timber A (Jiff. 700). 



2. The height of the vertical pipe E, supplying the clear water, through the 

 regulating cocks to the hutches F, will be best determined by experience. Of the four 

 regulating cocks, the sketch only shows one of the lower pair, viz, those through which 

 the clear water passes before entering the pipes A, G. 



3. The brass wire sieves H, on wood grids fastened with copper nails on the wood 

 cross bars Q, should be set level sideways, about ^ inch lower at the outlet than at the 

 opposite end, and packed around the sides and ends with hemp or other suitable 

 material. The side pieces c, and end pieces T, must be properly set in their places, 

 and the whole secured by a wedge behind the outlet end of the side pieces. 



4. The distributor i, and feed launders z, should then be placed in position, and 

 the regulating outlet arrangement J, applied. In this regulator there is a hole at both 

 the front and the back. The holes that are found to be least convenient for discharging 

 into the ore boxes should be fitted with wood-plugs K. To prevent an accumulation 

 of stuff too light to pass through the 'bedding,' yet too heavy to be carried over the 

 lips of the hutches, 'ragging-gear' is furnished. This consists of brass taper plugs, 

 with wrought-iron stems, the stems being screwed and fitted with regulating thumb- 

 screws, acting above and below the wrought-iron bridges Y. These plugs fit into 

 bevelled brass seatings fixed in the sieving H. By regulating the height of these 

 plugs, any undue accumulation of stuff is prevented. 



