HOW THE MINES ARE WORKED.
When the upper line of bonanzas had been worked out, and the shafts were
sunk to greater depths in search of new bodies of ore, they eventually
attained such a depth as brought them down upon the barren syenite
forming the west wall. The shafts were then deflected from the vertical
and passed down along the syenitic foot-wall to the eastward, in the
shape of an incline. At length it was seen that these inclines were
becoming too long to permit of their being worked through to advantage
with the machinery then in use, and company after company moved to the
eastward, a distance of a thousand feet or more, and then established a
new line of shafts, over which they set up new and more powerful
machinery than had yet been seen on the lead. These shafts did not
strike the lead until they had been sunk to the depth of one thousand or
one thousand two hundred feet, whereas the first line of shafts were
either sunk on the lead, or at such a distance in front of the croppings
as to tap it at the depth of from two to five hundred feet.
A third line of shafts had been commenced in 1875, and one of these,
which is now being sunk by the Savage, Hale, & Norcross, and the
Challar-Potosi Companies combined, is nearly a mile east of the
croppings. This is intended to be a shaft for all time. It will be of
vast size, containing several spacious compartments for hoisting and
pumping purposes, and will be supplied with the most powerful machinery
that can be manufactured. It will require some years to sink this shaft
to a point where it will intersect the vein; meantime the several
companies will continue to work through their present shafts and
inclines.
[Illustration:
WASTE ROCK DUMPS.
(_Challar, Potosi, Savage, Hale & Norcross Mines._)
]
The Savage Company are prepared to sink the incline of their present
shaft to the great depth of four thousand feet. For this purpose they
have set up new hoisting machinery of novel construction and of the most
powerful description. The reel on which the hoisting-cable winds is a
novelty for the first time introduced on the Comstock lode, and a brief
description of it and the cable used upon it may not be without interest
for the general reader.
The reel is fifteen feet in length, and at the larger end is twenty-two
feet in diameter, while at the smaller end the diameter is but thirteen
feet. It is suspended upon a wrought iron shaft about sixteen inches in
diameter, the ends of which revolve in ponderous bearings supported by
foundations of cut stone reaching into the earth to solid rock. The
shell of the reel is covered with thick wooden staves, and the whole
somewhat resembles a great tapering cask. Over the staves are securely
bolted heavy iron plates forming a strong armor outside of the wooden
structure. In this iron armor is a deep groove which, starting at the
smaller end of the great conical drum, runs in a spiral manner to the
larger end; just as the groove between the threads of a screw is seen to
run. In this groove winds the cable as the incline-car (“giraffe”) is
let down into or drawn up out of the mine.
When the car is at the bottom of the incline, the greater part of the
cable is off the reel, and when the hoisting begins it is wound up on
the smaller end of the drum, where the engines have greater purchase on
the load. As the hoisting proceeds, and the weight to be raised becomes
momentarily lighter, on account of the heavy steel cable being wound up,
the lifting force is steadily moved toward the larger end of the drum,
and each revolution adds to the swiftness of the ascent of the car that
is being raised. The cable is round, and is made of the best steel wire.
It is 4,000 feet in length, and weighs 25,190 pounds. The upper part,
for a distance of 1,500 feet down, is two inches in diameter; for the
remainder of its length, 2,000 feet, it gradually tapers till at the
lower end its diameter is one and three-quarter inches. The taper is not
made by dropping wires in the several strands of the rope, but by
drawing each wire (as it is manufactured) slightly tapering for the last
2,500 feet of its length.
The incline hoisting-works stand a short distance from the building in
which is contained the hoisting machinery of the vertical shaft, and the
cable, after entering the latter building, is carried over a large iron
pulley or sheave that is placed over the main shaft. Thence it passes
down a compartment of the main shaft a vertical distance of 1,300 feet,
when it passes _under_ a second sheave and continues down the incline to
its bottom.
The car used in the incline runs on an iron track, holds about five tons
of rock, and is capable of hoisting (easily) from 480 to 500 tons per 24
hours. The car is made wholly of iron and steel.
When this incline car has been hauled up as far as the bottom of the
vertical shaft, that is, to within 1,300 feet of the surface, it there
dumps its load by means of a self-acting gate in its bottom. The rock
thus dumped from the incline-car is then taken in smaller cars and sent
to the surface on cages that ply up and down the hoisting-compartments
of the main vertical shaft.
The engines for driving the huge reel, and thus hoisting this iron car
or “giraffe,” with its load of ore and the 25,000 pounds of cable, are
two in number and of 200-horse power each. A precisely similar hoisting
apparatus has since been set up at the Ophir mine; indeed, the drawings
for this powerful machinery were first made for the Ophir Company. The
length and weight of cable at the Ophir is the same as that in use at
the Savage mines.
Some of the old shafts opened on and about the first or upper line of
bonanzas have quite gone to decay. They still stand, but the timbers in
many places, far down in the bowels of the earth, are racked and rotten;
while the timbers built up in the mine to support the chambers from
which ore was extracted, and set up in the galleries, drifts,
cross-cuts, and chutes, millions on millions of feet in all, have quite
gone to decay. It is perilous to undertake the exploration of these old
worked-out levels. In many places they are caved in every direction, the
old floors are rotten, water drips from above, a hot musty atmosphere
and almost stifles the explorer, and in places, the air is so foul that
his candle is almost extinguished.
Down in these deserted and dreary old levels, hundreds of feet beneath
the surface, are encountered fungi of monstrous growth and most uncouth
and uncanny form. They cover the old posts in great moist,
dew-distilling masses, and depend from the timbers overhead in broad
slimy curtains, or hang down like long squirming serpents or the twisted
horns of the ram. Some of these take most fantastic shapes, almost
exactly counterfeiting things seen on the surface. Specimens of these
are to be seen in most of the cabinets of curiosities in Virginia City.
Some of the fungi that grow up from the bottoms of old disused drifts
are wholly mineral and are composed of minute crystals of such salts as
are contained in the earth from which they spring.
These old, decaying places breed all manner of gases, some of them, as
the firedamp (carburetted hydrogen gas), dangerous to human life.
One winter night, in 1874, some of the residents of the western part of
Virginia City were startled by seeing what seemed a column of flame
fifty or sixty feet in height, shooting up from the mouth of an old
shaft near the old upper works of the Ophir Company. It was at first
thought that the timbers in the old mine were on fire, and three or four
men ran to the spot to see what could be done toward smothering the
flames.
On reaching the shaft, however, they found that there was no smell of
smoke, and also that the supposed fire was a light unlike anything they
had ever before seen, in its weird whiteness and the strange
coruscations of its component particles, the light shed about by the
flame, the faces of the men were of a corpse-like pallor. Their clothing
and hair also partook in some degree of the same ghastly and unnatural
hue. The light came up the full size of the large square shaft, and seen
at a distance, as it rose through the falling snow, closely resembled
one of the shooting spires of the aurora borealis, and it exhibited
something of the same waving and inconstant motion.
Although the men felt creeping over them a sort of superstitious awe,
they still had sufficient courage to approach the shaft and gaze into
it. A strange sight was there seen. The whole interior of the shaft
seemed to be at a white heat, and glowed like a furnace. The timbers on
the sides were particularly brilliant. Each splinter, excrescence, or
bit of fungus seemed darting dazzling rays that streamed steadily out in
all directions. A warm, strange current of air ascended from the
sweltering regions below, and there was observed a musty, sickening
smell. All of those who looked into the shaft afterwards felt a severe
pain in the temples, and two or three were made sick at the stomach.
This strange appearance lasted over half an hour, and before it ended a
crowd of a dozen or more miners returning from their work had collected
about the shaft. The light died out from the top downwards, and
protuberances from the sides of the shaft continued to glow for some
minutes after the light was no longer visible at its top. This
remarkable phenomenon was undoubtedly caused by the belching forth of a
highly phosphurated gas of some kind from the deep, underground chambers
of the old abandoned works. The rush of this gas was probably caused by
an extensive cave in a place where the timbers had rotted away. One of
the men who witnessed the spectacle was of the opinion that the mingling
of the gas from the mine with the atmospheric air had something to do
with intensifying the light. He observed in the ascending current of
pseudo-flame myriads of small particles of some substance of a
floss-like texture, which appeared to flash and glow as they darted
upward, and which presented in the general column of light much the same
appearance as motes moving about in a sunbeam.
In February, 1874, some miners at work in the Utah mine, just north of
Virginia City, were all made temporarily blind by certain water or gases
which they encountered. They were running a drift at the depth of 400
feet to connect with some old, flooded works. When the end of the drift
neared the old works, the water they contained began to be drained off.
The water had attained a great height, and the pressure was so strong
that it sent streams darting and hissing from every hole and crevice in
the rock in which the drift was being run. In places, these streams of
water spurted out with as much force as though they had been thrown by a
hydraulic pipe.
The water, or the steam and gases from it, poisoned all who worked in
the drift. Their heads and faces were so swollen that their eyes were
closed, and all were thus rendered blind for some days. A few years
before, the same thing occurred in the Savage and the Yellow-Jacket
mines, when drifts were run to tap old flooded works in which rotten
timbers were soaking. Quite recently, all the miners at work in the
Sutro Tunnel were poisoned, and had their eyes closed for some days by
the tapping of a shaft which had been filled with water for two or three
years. All who are thus poisoned speedily recover by remaining above
ground for three or four days.
[Illustration]