This,
but at another tunnel, was afterward modified by placing a separate
hurdy-gurdy on a sleeve on each drill-rod; the advance movement of the
drill being given by hydrostatic pressure on an annular piston, thus doing
away with all gearing. These eight sets of machinery were run for nearly
21/2 years' time; the only break being that of a spur-wheel, doubtless
caused by the careless dropping of a steel bar between it and its pinion.
Aside from this accident, practically not a dollar was spent for repairs,
and the machinery, including the pipe, was in about as good order when the
tunnel was finished as when it was first erected. One man, on a twelve
hour shift, operated the machinery at each shaft, besides dumping the
cars; two men kept the 18 pumps on the line in order, the principal work
being in keeping the suction-pipes for the down-grade headings tight; thus
a force of 18 men was only required for the eight shafts. The cost of the
pipe, gates, etc., when put in place, was $14,631, and of the machinery
about $60,000.
[Illustration: FIG. 14.]
At the Idaho gold quartz mine, situated near Grass Valley, California,
water-power has been introduced during the past year (1883), taking the
place of steam. The supply main is of wrought-iron, 22 inches in diameter,
8,764 feet long, buried in the ground below frost-line.
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