MINING. 129 
s. os 
upon the power of the machinery employed to raise them. For raising 
ore from a moderate depth a common windlass (pl. 26, jig. 28) may be 
employed. For greater depths and larger loads horse and steam-power are 
used. ig. 27 represents the application of a steam-engine for the purpose 
of raising coals. It works in two shafts at once, the empty corves descend- 
ing in one while the full ones are coming up in the other. In this way the 
weight of the material only is required to be overcome by the engine, the 
descending and ascending corves balancing each other, an arrangement 
which should always be attended to. 
In cases where a mine has a capacious adit, or when material must be 
introduced to fill up the spaces from which the ore has been removed, the 
ascent of the corves is caused by the descent of vessels filled with water or 
rocks ; the velocity is regulated by brakes. The same means are employed 
to draw up the ores on inclined planes, the lower part of one of which is 
seen in jig. 26 a, which also shows the manner of loading the car, mu. A 
dog, a, filled with ore is weighed by an apparatus indicated in the figure, 
and is then allowed to tilt over and discharge its load into the car, m, by 
withdrawing the bolts which hold it down to its truck. 
fig. 23 represents a car which is frequently used on inclined planes. 
figs. 24a and 25 show the usual contrivance for unloading large cars. The 
last sills of the railroad on which the car runs are movable about pivots, 7 ; 
when the car comes on them, they are held in the horizontal position by the 
hooks x and y ; after attaching the car by the chains, c, and drawing the bolt, 
u, of the end of the car, the hooks, # and y, are thrown out by means of the 
lever d, when the frame will be tilted by the weight of the car, and the load 
discharged. It requires but little force to replace the frame afterwards in 
the horizontal position, when the car will again be on the track. 
The descent and ascent of the miners take place on single or double 
ladders (pl. 24, fig. 87), on winding stairs (jig. 86), in the corves (jig. 38), 
or on an especial seat attached to the rope (jig. 389). In France, Belgium, 
and England, the latter modes are common, but in the Prussian coal mines, 
in the Hartz, and in Cornwall, the common ladders are in general use, in 
consequence of which much time and force are spent by the miners in 
the ascent, more particularly through shafts of a depth of 1,200 to 2,000 
feet. 
9, DRAINAGE oF Minzs. 
When the workings are above the level of a valley at no great distance, 
the drainage is generally effected by an adit level, which is a slightly 
inclined subterraneous canal emptying the waters of the mine near the 
lowest level of the valley. Such a slope only should be given to it as is 
just sufficient to make the water run, in order to drain the mine at the 
lowest possible level. This method of drainage is always the surest where 
it can be effected, and notwithstanding the great first outlay is generally 
the most economical. 
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