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MINING IN CALIFORNIA AND NEVADA.
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19
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PERCUSSIVE ROCK-BORING MACHINERY.
In view of the great expense and, comparatively speaking, the slow
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progress made with
mining operations if carried on by means of manual labor, the
Californians possess a number of machines which take the place of
boring ef holes, for blasting, by hand. Amongst these the Victor hand
drill was seen at work, the special advantages claimed for it being a
greater rapidity in boring; but as this drill, which was raised in the
same manner as the shank of a stamp-head, and turned likewise by the
lifters, depended in a very considerable measure upon a couple of
powerful steel springs to aid the force and weight of the blow, it was
seen that the strongest effects were achieved if the drill bored
vertical or nearly so. At the same time it required two men constantly
at the two handles fixed at each side on small fly-wheels, who would
have hard work to attend to the boring for three or four hours at a
stretch. Any holes bored at and more or less above the horizontal
compared unfavorably with ordinary miners' work, though for quarry and
open cutting work it would appear suitable.
Taking
into consideration the primary outlay for such " power drills " if
driven either by compressed air, water, or steam pressure, the costs of
repairing them, and the additional motive-power of any kind required,
it is agreed upon that the introduction of such labor-saving machines
would in future reduce the working expenses one-half, but undoubtedly
admit also of a greater speed being obtained in opening new ground, or
in working our quartz lodes, than what we have been accustomed to
hitherto. For-as-much those power drills, as driven by njeans of
compressed air, act likewise as very powerful ventilators, through the
cold exhaust air they emit or discharge every piston-stroke, driving
out all depraved gases in the workings, the miners can perform a larger
amount of work there than in hot and unwholesome air ; and it may be
added that they do about 50 per cent, more work than a similar number
of miners would perform as those needed for the working of each of
these drills. In the absence of my original diagrams of such drills, I
can but give a brief description of such machines, to which a number of
rules will, however, be added that may be found useful by those who
have not had any opportunity of working them, or who have not seen them
at work. These power drills resemble, in their principal parts, engines
of a small calibre, having, however, several essential parts added for
the due performance of the special work alloted to these borers. There
is the ordinary cylinder, from 3£ to 6 inches in diameter, a slide
valve, piston, and rod, with the necessary air, water, or steamports,
to admit the motive-power used, which latter stands in the following
proportion, in accordance with practical experience, viz., air, water,
and, lastly, steam. There are besides two outlets, viz., for the
exhaust and for the compressed air, which is conveyed by means of
strong gas pipes —malleable iron chiefly—to a receiver, which is
furnished with a proper pressure gauge, to show the pressure per square
inch. There being but one stuffing-box, the piston-rod protrudes
through same, having the "drill-bit" proper geared to its outer end by
means of an adjustable " chuck," and, on the turning on of
motive-power, the piston and drill-bit perform their ordinary work by
back and forward strokes, and by means of greater pressure these
strokes are propelled with increased force against the rock, the
drill-bit at the end of the piston-rod indenting the latter with a
power ranging from nothing to a weight of 1,000 lbs. each stroke. In
order to give the drill-bit the requisite turn each stroke, to enable
it to bore a perfectly
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