CRANE. | Correlation. 325 
or blasted out, allowing the roof to fall upon the sills and other 
remaining timbers of the drifts. Work in the deposit is then 
continued by a series of sub-side drifts extending across the 
deposit laterally, and the operation is repeated from above 
downward until the deposit has been exhausted. 
Transporting. 
The ore, having been loosened, is transferred to the foot 
of the shaft, usually in tubs, placed upon small cars, and 
trammed by man power. At the shaft, the bucket is trans- 
ferred from the car to the hoisting rope or cable, and is thus 
brought to the surface. 
As most of the shafts are at some distance from the con- 
centrating plants, the ore must be trammed from the shaft 
to the mill, usually on a high trestlework, which supports 
the track upon which the cars are run back and forth. 
In some cases self-acting planes are employed in transfer- 
ring the ore from the shaft to the mill, and the empty car 
from the mill to the shaft. 
Hoisting. : 
The ore is hoisted from the mine in wooden or iron buck- 
ets, holding from 200 to 500 pounds. Ropes or cables are 
employed as the hoisting medium, which are wound upon 
some form of hoisting apparatus, such as the horse-power 
hoist, or whim, or some form of friction gear steam hoist. 
In a few instances whims of the Mexican malacate type are 
employed, which are drums mounted on a vertical shaft 
turned by horse power. 
As yet cages are of rare occurrence, as the mining opera- 
tions have not extended to sufficient depth to warrant the 
employment of the same, and, therefore, the capacity of the 
hoisting apparatus used at present is limited. 
Sizing. 
The mine-run material on entering the mill is, in some 
cases, passed over parallel bar screens or grizzlies to separate 
the finer material from the boulders, which have to undergo 
further reduction, usually by means of the sledge. 
Other forms of sizing apparatus, such as rotating and 
