BELOW THE WATER-DEPOSITS.
In countries where no mining is done it is the prevalent opinion that at
a certain depth the earth is full of water, and that the deeper we go
the more water will abound. This is a mistaken notion. After delving
beyond certain bounds, water ceases to be generally disseminated in the
earth. This is after we have gone below the “scalp” or surface-water of
the country. Until we have passed through this scalp, water is found
almost everywhere. This being the case, it is quite natural that persons
residing in countries where wells sunk in search of a supply of water
are the deepest works of the kind undertaken, should imagine
overwhelming floods of water to exist everywhere far down in the bowels
of the earth.
In Nevada—and the rule probably holds good in every country—after
passing the more open and softer matter—drift and rock—there is reached
the solid rocky mass forming what might be termed the “skull” of the
earth—the hard shell lying between the comparatively spongy exterior
strata, and the molten interior mass. This intermediate shell of hard
rock is where the miners along the Comstock are now delving in all the
deeper mines. Here we find that solid rock takes the place of water in
most situations—solid rock is the rule. When the rock is not solid and
perfectly homogeneous, there water finds its way and forms subterranean
reservoirs of all sizes and shapes, which, in mining parlance, are
called “pockets.”
These pockets may be of almost any shape, but are generally in the form
of a crevice. As a rule, the crevices are not open spaces like caverns,
but are filled with some permeable material into which the water may
find its way and settle, as in the ground composing the “scalp” above.
The water at the depth of from 1,000 to 2,000 feet lies in detached
bodies. In the country-rock (the rock lying on each side of a vein and
forming the general rock of the country) there are fewer of these
pockets of water than within the bounds of a vein, as the solidity and
homogenous character of the outside rock leaves no space in which water
may be contained. The Comstock lode occupying an immense fissure,
extending into the intermediate crust of the earth to an indeterminate
depth, there are naturally many openings in it, through which water may
descend; besides, the material of which the vein is composed is in
general much softer, and therefore more pervious than the great mass of
rock outside of the vein. The pockets of water are confined within walls
of clay or hard, impervious rock. Thus drifts may be run on all sides
of, and even under, these subterranean reservoirs, and no water is seen
until the confining walls are cut. When a body of clay is encountered
and there is reason to suspect that a body of water is being approached,
a long drill is used with which to feel the way in advance of the drift,
and let the water out, if any there be, in a controllable stream. Were
the miners to push ahead with a drift of full size, the pressure of
water would presently burst in the whole face of their opening, tear
down the timbers, cause extensive caving of the ground, and perhaps
flood everything and drown the men before they could escape.
When once the works of a mine have been carried down into the solid
shell of the earth, the work of draining any body of water that may be
encountered is a mere question of time. If the underground cistern is
small it is soon pumped out; if large it takes a proportionally longer
time, the same pump being used in each case; but, sooner or later, it
must be exhausted. If water were not thus found in detached bodies
(instead of being universally diffused) in that zone of the earth under
consideration, there could be mining under seas, lakes, and rivers, as
is now successfully practiced in many countries.
In illustration of the manner in which miners often drift under and
around bodies of water, I may give an incident of the early days of
Washoe, when drifts and tunnels had not yet drained off the
surface-water, and wells were yet a possibility in Virginia City.
[Illustration: THE MISSING WELL BOTTOM.]
A lady resident of the town one day went to a well in her door-yard to
draw some water. Being in haste, she let the bucket go down from the
windlass “by the run,” and the instant it struck the water out dropped
the whole bottom of the well. Every drop of water instantly disappeared
and nought was seen where it had been, but a black, yawning chasm in
which hung and dangled the bucket. Amazed almost beyond the power of
speech, the lady for a time stood and gazed into the bottomless well,
then rushed to the house. She had considered the matter and comprehended
it.
“What did I tell you?” cried she, addressing her rather easy-going
husband. “I knew that the men who dug that well were taking no pains
with their work!”
“What is the matter now?” said the husband.
“Matter?—matter enough! The bottom has dropped out of the well!”
“Bottom dropped out of the well!” exclaimed the husband, beginning to
become interested.
“Yes: the bottom has dropped out of the well, and I am not at all
surprised—I am not one bit astonished! I knew when I saw the men putting
the bottom in that well that it would never be of any account!”
The cause of the accident was simple enough. The well had been dug in
the line of a tunnel advancing from a distant point below. The miners,
all unconscious of the presence of the well, had drifted under it, and
at no great distance below its bottom. Being without adequate support
the bottom must soon have fallen out, of its own accord, but the sudden
jar of the bucket on the surface of the water undoubtedly precipitated
the event. A peculiar kind of clay is found in many places on the
Comstock lode which is not a little curious on account of its creeping
propensities. A stratum of this clay will be seen to crawl out into
tunnels and other openings in a manner much resembling the action of the
toy known as Pharaoh’s serpents. You are unable to see where it is
coming from or what moves it, yet it is constantly crawling out into all
the openings that reach it.
In places where drifts have been run into this clay it is necessary to
keep one or two men constantly at work at cutting it away in order to
keep the drifts open and passable. This is not owing to the slaking and
swelling of the exposed surface, as in that case after a few removals of
the surplus material a hole would be left, and there would be no more
trouble. The whole body of the clay appears to be creeping. It has the
almost imperceptible motion of the glacier, irresistibly advancing,
crushing everything in the shape of timbers that may be placed before
it. All that can then be done is to set men to work at cutting it off as
fast as it comes out. The cause of this creeping is probably to be found
in the pressure, of the superincumbent or surrounding strata of rock.
Its motion is not unlike that seen in the straightening out of a piece
of pith that has been compressed. There is a limit to this creeping
power of the clay, but it is not reached till many feet have crept out
into the drift, tunnel, shaft, or chamber, and have been cut off and
removed. Its actions is so mysterious that some of the miners are ready
to explain it by saying that the clay comes out and fills up the drifts
because “Nature abhors a vacuum.”
If left to its course the clay would very soon close up the drift, as
completely as if none had ever been made. Thousands of feet of drifts
and tunnels in the mines are closed in this way.
In the Caledonia mine, American Flat, much trouble was experienced with
this creeping clay. On one occasion a streak of it two or three feet in
width continued to rise from the floor of a tunnel until over thirty
feet had thus come up and been cut off. It is bad anywhere, but is most
mischievous in the main shaft. For this reason mining men always seek a
spot in which to put down such shafts, where they are likely to pass
through solid “country-rock” to a great depth below surface. The sad
experience of early days taught them this lesson. The clay is generally
found within the wall of the vein. It abounds in the mines south of Gold
Hill, about American Flat. The ordinary clay found next to the foot, and
hanging walls in all mines is liable to swell—on account of the lime it
contains—when exposed to atmospheric action, but after the pressure on
the timbers has been eased by cutting away behind them a few times,
there is no more trouble.
The power of this swelling, slacking clay is immense. It crushes in, and
splinters all the timbers that can be placed before it: it somewhat
resembles the power exerted in the expansion and contraction of large
masses of iron, as seen in iron bridges and similar structures. The
following curious Comstock “find” may be of interest to some readers.
In working out the first or upper bonanza of the Ophir mine, there was
brought to light a human skull of a very ancient and curious type. The
skull was dug out where a drift was being run in the ore-body at a depth
of about three hundred feet below the surface. It was brought out, and
dumped with a car-load of ore, not being observed by the miners. United
States District Judge A. W. Baldwin, since killed by a railroad accident
in California, happened to be present when the car-load of ore was
dumped. Seeing an object of peculiar shape roll toward his feet among
the ore dumped from the car, the Judge picked it up, and found it to be
a human skull of a peculiar form and thickly crusted over with sulphuret
of silver. He carried it into town and presented it to Wm. Shepard, of
the firm of Tinker & Shepard, who placed it in a cabinet of curiosities,
where it still remains.
The skull attracted no attention outside of Virginia City until 1874,
when, mention being made of it in the newspapers, the Academy of
Sciences, of San Francisco, sent for it for the purpose of making a
critical examination of it. While it was in San Francisco a plaster cast
was made of it, and at a meeting of the Academy of Sciences, Dr. Blake
exhibited the cast and spoke of it as follows: “There is in this skull a
peculiarity that is seen in some of the ancient Peruvian skulls, namely,
on interparietal bone. The general _contour_ of the skull is of a very
low type; the anterior portion is very slightly developed and receding;
the hinder portion is largely developed. It bears a similarity to the
skull of the carnivorous apes, the cavity for the lower jaw-bone being
very deep and not allowing of any grinding motion of the jaws. The skull
when found was covered with a metallic layer. It is of a different type
from any that have been found, and belonged to a carnivorous man, who
could walk easier on all fours than on two feet.” Several ancient
Peruvian skulls were then produced in order to show the interparietal
bone.
Professor Whitney was very anxious to be allowed to send the skull to
the Atlantic States and Europe, but the owners would not part with it
for that purpose. The plaster cast taken was sent to Dr. J. Wyman, of
Cambridge. It would seem that the conclusion arrived at in San Francisco
was that the skull was that of a man belonging to a pre-historic race.
He probably was adorned with a tail. At the time the great fissure was
formed in which the Comstock lode was deposited, or perhaps at the time
the fissure was being filled with its rich ores, this pre-historic
creature was probably fooling about the edge of the chasm, looking down
into it to see what discoveries he could make, when the earth crumbled
beneath his weight, and he rolled down and was incorporated in the heart
of the vein. His sad fate must have proved a salutary warning to all
others of his tribe, as his skull is the only thing in the way of
ancient human remains that has ever been found in any mine on the lode.
[Illustration]
[Illustration: THE MAN-EATER]