The No. 1 Camphausen shaft, near Fishbach,
in the department of the Saarbruck
Collieries, Prussia. 1,650
Now, taking the mines of the Comstock for a distance of over a
mile--from the Utah on the north to the Alto on the south--there is
hardly a mine that is not down over 2,500 feet, and most of the shafts
are deeper than those mentioned above; while the Union Consolidated
shaft has a vertical depth of 2,900 feet, and the Yellow Jacket a
depth of 3,030 feet. In his closing argument before the Congressional
Committee on Mines and Mining in 1872, Adolph Sutro of the Sutro
tunnel said: "The deepest hole dug by man since the world has existed
is only 2,700 feet deep, and it remains for the youngest nation on
earth to contribute more to science and geology by giving
opportunities of studying the formation of mineral veins at a greater
depth than has ever been accomplished by any other nation in the
world." Mr. Sutro was of the opinion that the completion of his tunnel
would enable our leading mining companies to reach a vertical depth of
5,000 feet.
This great depth has never yet been attained except in a bore hole or
artesian well. The deepest points to which the crust of the earth has
ever been penetrated have been by means of such borings in quest of
salt, coal, or water. A bore hole for salt at Probst Jesar, near
Lubtheen, for the Government of Mecklenberg-Schwerin, is down 3,315
feet, the size of which bore is twelve inches at the top and three
inches at the bottom. A bore hole was put down for the Prussian
Government to the depth of 4,183 feet. But in these bore holes the
United States leads the world, as there is one near St. Louis, Mo.,
that is 5,500 feet in depth. Here on the Comstock, in the Union
Consolidated mine, a depth of 3,300 feet has been attained, but not by
means of a single vertical shaft. The vertical depth of the shaft is
2,900 feet; the remainder of the depth has been attained by means of
winzes sunk from drifts. Several long drifts were run at this great
depth without difficulty as regards ventilation or heat.
The combination shaft is situated much further east (in which
direction the lode dips) than any other on the Comstock. It is 3,000
feet east of the point where the great vein crops out on the side of
Mount Davidson; 2,200 feet east of the old Chollar-Potosi shaft, 1,800
ft. east of the old Hale & Norcross (or Fair) shaft, and 2,000 ft.
east of the Savage shaft. Thus, it will be seen it is far out to the
front in the country toward which the vein is going. The shaft is sunk
in a very hard rock (andesite), every foot of which requires to be
blasted. The opening is about thirty feet in length by ten feet in
width. In timbering up this is divided into four different
compartments, some for the hoisting and some for the pumping
machinery, thus presenting the appearance at the top of four small
shafts set in a row. Over the shaft stand several large buildings, all
filled with ponderous machinery.
The Sutro drain tunnel (nearly four miles in length) connects with the
shaft at a depth of 1,600 ft., up to which point all the water
encountered below is pumped. The shaft was sunk to the depth of 2,200
ft. before more water was encountered than could be hoisted out in the
"skips" with the dirt. At the 2,200 level two Cornish pumps, each with
columns fifteen inches in diameter, were put in. At the 2,400 level
the same pumps were used. On this level a drift was run that connected
with the old Hale & Norcross and Savage shafts, producing a good
circulation of air both in the shaft and in the mines mentioned. At
this point, on account of the inflow from the mines consequent upon
connecting with them by means of the drift, they had more water than
the Cornish pumps could handle, and introduced the hydraulic pumps,
which pumps are run by the pressure of water from the surface through
a pipe running down from the top of the shaft, whereas the Cornish
pumps are run by huge steam engines.
By means of the hydraulic pumps they were enabled to sink the shaft to
the 2,600 level, and extended the Cornish pumps to that point, where
another set of hydraulic pumps was put in. They then sunk the shaft to
the 2,800 level, when they ran another drift westward, and tapped the
vein. The prospects at this depth in the Hale & Norcross and Chollar
mines were so encouraging that the management decided to sink the
shaft to the depth of 3,000 ft. On reaching the 3,000 level, they ran
a third drift through to the vein. The distance from the shaft to the
east wall of the vein was found to be only 250 ft. At the depth of
3,000 ft. they put in one of the pair of hydraulic pumps that is to be
set up there. The second pump is now arriving from San Francisco, and
as soon as the several parts are on the ground, it will be at once put
in place alongside its fellow on the 3,000 level. This additional pump
will increase the capacity from 600,000 to 700,000 gallons in
twenty-four hours, or about forty-five miners' inches.
Owing to the excellent showing of ore obtained on the 3,000 level by
the Hale & Norcross Company, and to the continuation of the ore below
that level (as shown by a winze sunk in the vein), the management
determined to sink the shaft to the vertical depth of 3,200 ft. It is
now 3,120 ft. deep, and it is safe to say that it will reach the depth
of 3,200 ft. early in September, when it will lack but eighty feet of
being as deep as the shaft at Przibram was at the time of the great
festival. Although the shaft is of great size--about thirty feet by
ten feet before the timbers are put in--the workmen lower it at the
rate of about three feet a day, in rock as hard as flint.
The hydraulic pump now working at the 3,000 foot level of the shaft is
the deepest in the world. In Europe the deepest is in a mine in the
Hartz Mountains, Germany, which is working at the depth of 2,700 feet.
It is, however, a small pump not half the size of the one in the
Combination shaft. Although these pumps were first used in Europe,
those in operation here are far superior in size, and in every other
respect, to those of the Old World, several valuable improvements
having been made in them by the machinists of the Pacific coast.
The capacity of the two Cornish pumps, which lift the water from the
2,900 foot level to the Sutro drain tunnel (at the 1,600 level), is
about 1,000,000 gallons in twenty-four hours, and the capacity of the
present hydraulic pumps is 3,500,000 gallons in the same time. They
are now daily pumping, with both hydraulic and Cornish pumps, about
4,000,000 gallons, but could pump at least 500,000 gallons more in
twenty-four hours than they are now doing. The daily capacity with the
hydraulic pump now coming, and which will be set up as mate to that
now in operation at the 3,000 foot level, will be 5,200,000 gallons.
The water which feeds the pressure pipe of the three sets of hydraulic
pumps is brought from near Lake Tahoe, in the Sierra Nevada Mountains.
The distance is about thirty miles, and the greater part of the way
the water flows through iron pipes, which at one point cross a
depression 1,720 feet in depth. The pressure pipe takes this water
from a tank situated on the eastern slope of Mount Davidson, 3,500
feet west of the shaft. At the tank this pipe is twelve inches in
diameter, but is only eight inches where it enters the top of the
shaft. The tank whence the water is taken is 426 feet higher than the
top of the shaft, therefore the vertical pressure upon the hydraulic
pump at the 3,000 foot level is 3,426 feet. The pressure pipe is of
ordinary galvanized iron where it receives the water at the tank, but
gradually grows thicker and stronger, and at the 3,000 level it is
constructed of cast iron, and is 2½ inches in thickness. The pressure
at this point is 1,500 pounds to the square inch.
In the early days of hydraulic mining in California the miners thought
that with a vertical pressure of 300 feet they could almost tear the
world to pieces, and not a man among them could have been made to
believe that any pipe could be constructed that would withstand a
vertical pressure of 1,000 feet; but we now see that a thickness of
two and a half inches of cast iron will sustain a vertical pressure of
over 3,400 feet.
There is only one pressure pipe for all the hydraulic pumps. This
extends from the tank on the side of the mountain to the 3,000 foot
level. It is tapped at the points where are situated the several sets
of hydraulic pumps. The water from the pressure pipe enters one part
of the pump, where it moves a piston-back and forth, just as the
piston of a steam engine is moved by steam. This water engine moves a
pump which not only raises to the surface the water which has been
used as driving power, but also a vast quantity of water from the
shaft, all of which is forced up to the Sutro drain tunnel through
what is called a return pipe. Each set of hydraulic pumps has its
return pipe; therefore there are three return pipes--one from the
2,400, one from the 2,600, and another from the 3,000 level.
Some idea may be formed of the great size of these hydraulic engines
when it is known that the stations excavated for them at the several
levels where they are placed are 85 feet long, 28 feet wide, and 12
feet high. All this space is so filled with machinery that only
sufficient room is left to allow of the workmen moving about it. One
of these stations would, on the surface, form a hall large enough for
a ball room, and to those who are unacquainted with the skill of our
miners it must seem wonderful that such great openings can be made and
securely supported far down in the bowels of the earth; yet it is very
effectually done. These great subterranean halls are supported by
timbers 14×16 inches square set along the walls three feet apart, from
center to center, and the caps or joists passing overhead are timbers
of the same size. The timber used is mountain spruce. Not one of these
huge stations has thus far cost one dollar for repairs. The station at
the 2,400 level has been in use five years, that at the 2,600 three
years, and the one at the 3,000 level eight months. Room for
ventilation is left behind the timbers, and all are still sound.
Timbers of the same kind are used in the shaft, and all are sound. The
shaft has cost nothing for repairs. Being in hard andesite rock from
top to bottom, the ground does not swell and crowd upon the timbers.
If it shall be thought advisable to go to a greater depth than 3,200
feet, a station of large size will be made on the east side of the
present shaft, and in this station will be sunk a shaft of smaller
size. The reason why the work will be continued in this way is that in
a single hoist of 3,200 feet the weight of a steel wire cable of that
length is very great--so great that the loaded cage it brings up is a
mere trifle in comparison. In this secondary shaft the hoisting
apparatus and pumps will be run by means of compressed air. As it is
very expensive to make compressed air by steam power, the pressure
pipe will be tapped at the level of the Sutro tunnel, and a stream of
water taken out that will be used in running a turbine wheel of
sufficient capacity to drive three air compressors. As there will be a
vertical pressure upon the turbine at this depth of over 2,000 feet, a
large stream of water will not be required. The water used in driving
the wheel will flow out through the Sutro tunnel, and give no trouble
in the shaft.
By means of this great shaft and its powerful hydraulic and Cornish
pumps the crust of the earth will probably yet be penetrated to far
greater depth than in any other place in the world. It has been only a
little over ten years since the work of sinking it was begun, whereas
in the mines of the Old World they have been delving since "time
whereof the memory of man runneth not to the contrary." The work on
the Combination shaft has been by no means continuous. There have been
long stoppages aside from those required at such times as they were
engaged in running long drifts to the westward to tap the vein, and at
times for many months, when the several companies interested in the
shaft were engaged in prospecting the various levels it had opened up.
* * * * *