|
MINING IN CALIFORNIA AND NEVADA.
|
17
|
||
|
|
|||
|
DRIVING OF LEVELS AND CROSSCUTS
does
not differ from our methods, except that, in some cases, "headers," or
smaller drives, are pushed on ahead the permanent level, and that
percussive drills are used in all these operations with good effect.
PUMPS.
The
Californian columns are nearly fac-similes of ours, although
constructed somewhat differently from the latter, without, however,
interfering with the principle of plungers and drajvlifts. The only
important feature requiring attention is, that they are all made of
stout boiler-iron plates, cut to size and riveted together so as to
form "break joints." Of course the " workings" and the flanges riveted
to the pipes are made of cast iron, and they are pierced for the bolts
at the joints where necessary. The boiler plates are rolled and riveted
together in three lengths, of such diameter of lift as required, and
all the longitudinal and cross joints are riveted in zig-zag fashion.
The lifts are made in 12 to 16 feet lengths ; they are much lighter
than cast-iron lifts of the same size, and therefore need not such
heavy bearers and yokes in the shafts. The experience had with these
pipes for many years proves that they are much less liable to burst
under heavy pressure. They are, on the average, tested up to 300 or 360
lbs. per square inch pressure, and are also much freer from flaws, and
they last a deal longer, even in such mines where the mineral water
destroys extra thick cast-iron pipes in a very short time. As a further
preventative against mineral water, and especially hot to boiling mine
water, these lifts are covered with a series of coats of coal tar,
pitch, and asphaltum from time to time, which are a satisfactory means
to preserve them from injury.
AIR COMPRESSORS.
These
machines, as an auxiliary to mining, are in use with all the larger
companies, and have been found both economical and advantageous as
against manual and expensive labor. Inasmuch as these machines and the
percussive power drills are likely to find much favor with our miners,
I shall briefly describe them, and offer general directions for their
practical use. Air compressors consist generally of two principal
parts, viz., the motive-power as represented by a steam engine, and the
cylinder in which the air about to be compressed is manipulated. If the
steam engine is directly geared to the compressor, the direct action of
the former will save power, and therefore the effects are more
serviceable. The compressor is also a cylinder with piston complete,
like the steam cylinder, and they work generally end for end or
sideways. The compressor is set in motion by the crank shaft worked
from the end of the piston-rod of the steam engine, and as these
cranks, or rather solid discs, are working the air piston as well, the
air, sucked into the air cylinder by means of some kind of tumbler
valves, is compressed with every return stroke as the valves shut after
admitting the air sought to be compressed. The object and the aim of
all inventors has been to construct air compressors that will give a
high pressure of air, and at the same time obviate the difficulty
occasioned by the heat engendered during the process of its
compression. The results are not always satisfactory, owing to the
difficulty of confining the compressed air at the end of every stroke
by the piston, and to avoid its forming a cushion before it leaves the
air cylinder for practical use. To produce,
|
|||
|
|
|||