Crang.| Prospecting, Mining and Milling Machinery. 249 
the form where both drum and engine are combined, for the 
reason that either two men are required to operate it, or one 
must climb up and down the derrick in his care of boiler, 
engine, and drum. When, however, the engine and drum 
are separate, there is more room on the platform of the der- 
rick than is possible when both are combined. 
In the improved forms of hoisting engines, the framework 
of the engine and the drum support is one and the same. 
The engine operates the shaft bearing the small friction wheel 
that drives the drum. Two small friction wheels are gener- 
ally employed, especially in the larger machines, which neces- 
sitate a large friction wheel on both ends of the drum. An 
eccentric bearing is also placed on both ends of the drum 
shaft, so that the whole drum can be moved back and forth 
either against the friction wheels or in the opposite direction 
against the brake plate. By this arrangement of eccentrics, 
the power may be thrown on and off and the brake also ap- 
plied by the same movement. An additional braking move- 
ment is given or provided for, so that a finer adjustment and 
a further tightening of the brake may be obtained. 
Steam is furnished to these hoisting engines by feed pipes 
from the boiler plant at the mill, asmall boiler on the ground 
at the foot of the derrick, or a boiler placed on the platform 
of the derrick. The last method is the one usually employed, 
although the first-mentioned method is especially applicable 
where several shafts are grouped about one mill. 
The throttle is so arranged that it is opened and closed by 
means of a push rod or a combination of levers, which is 
placed within easy reach of the engineer. Figure 26. 
Cacres.—As the mining operations during the past have 
been to a great extent superficial, cages have not been em- 
ployed, as they cannot be used to advantage in shallow work- 
ings. The deeper mining of the past few years has necessi- 
tated, in a few cases, the introduction of cages, with improved 
shaft linings and hoisting machinery. 
The advantages gained in speed, safety and economy should 
warrant a speedy change from buckets to cages, and it is to 
be hoped that the use of cages will shortly become universal. 
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