8 



DRESSING OF ORES 



eye. The small diameter of the trommel is 3 feet 9 inches ; large diameter, 5 feet 

 4 inches ; length of trommel, 9 feet. The diameter of the trommel carrier wheel is 

 2 foot 6 inches, outside diameter of picking table 14 fout, inside diameter 10 feet; 



C44 



D n 



height of back of table, 6 inches ; height of table from ground, 2 feet 7 inches. The 

 table is composed of 16 cast-iron segments, each inch thick and 2 feet wide, 

 supported on 16 wooden arms. The table makes a speed of about 2 inches per second. 

 The length of picking line is 30 feet, which affords space for 15 or 16 pickers. This 

 number of hands will dispose of about 15 tons of stuff per hour, the size being from 

 1 to 3 inches, or one boy will select say 4 tons per day, and divide it into ore and 

 ' dradge ' work. 



Sagging (fig. 645). It has been remarked that, in breaking the lode underground, 

 numerous rocks are produced, throughout which valuable ore is more or less dissemi- 

 nated. After these stones are washed, they are ragged. This operation consists simply 

 in reducing the stones to a smaller size, and rejecting as many of the sterile stones as 

 can be readily picked out. The reserved heap is ultimately taken to the spallers and 

 cobbers. The weight of a steel-headed ragging hammer varies from six to eight pounds. 



Spalling (fig. 646), is usually performed by women. The object is to break the 

 stones to a proper size for the bucking hammer or crushing mill, and at the same time 



645 



to cast aside such lumps as are destitute of ore. The hammer employed is made of 

 cast steel, and is set upon a light pliant handle. Its weight is about sixteen ounces, 

 and its cost eightpence. A practised spallor will produce about one ton of stuff per 

 day, but the quantity must necessarily depend upon the hardness and nature of the 

 stone. 



Stone Breaker. This machine is specially adapted for reducing masses of vein- 

 stuff into sizes suitable for the cobbing floors and crushing mill. It can be driven 

 either by steam- or water-power, and consists of a crushing hopper, in which the 

 stone is broken between a pair of jaws, the one being fixed, the other actuated by 



