AIR AND WATER IN THE MINES.
Man is an air-breathing animal. So soon as his supply of air is cut
off he dies. In proportion as that supply is lessened or vitiated,
his physical and mental energies fail. One of the first requisites,
therefore, in all mining operations is that the ventilation shall be
good. To accomplish this end an air current must be established. It is
true that into any accessible cavity atmospheric air will rush, but
if it be allowed to remain in that cavity without any replacement it
becomes dead and unfit to breathe. If, in addition to this, it takes
up deleterious gases, like those which escape from the coal measures,
it becomes poisoned and dangerous to human life. Hence the necessity
of a continuous current. Provisions for such a current are made with
the opening into every mine. The separate air compartment of a shaft
has already been noticed. In drifts, tunnels, and slopes a part of the
opening is partitioned off for an airway, or, what is more common, a
separate passage is driven parallel with, and alongside of, the main
one. In drifts and tunnels, since the mines there are not deep, air
shafts are often driven at some other point above the workings, or
slopes are sunk from the outcrop to accommodate the return air from the
mine. It is due to the necessity of maintaining an air current that
all passages and chambers are driven in pairs or sets in the manner
already explained. It has also been explained how the fresh air going
in at the carriage ways of the shaft, or other openings, passes along
the gangway to its extremity, back along the airway, up to and across
the faces of each set of chambers, and then down into the airway again,
to be carried to the foot of the shaft and up by the air passage to
the surface. But in the larger mines there are many passages besides
the main gangway that must be supplied with air, and the current must
therefore be divided or split to accommodate them; so these separate
currents, taken in this way from the main current, and themselves often
divided and subdivided, are called “splits.” The air channels thus
branching, uniting, crossing, and recrossing form a most complicated
system of ventilation. But the current goes nowhere by chance. Every
course is marked out for it. On the fact that it follows that given
path depends the lives of the workmen and the successful operation
of the mine. Sometimes it becomes necessary to carry two currents of
air through the same passage in opposite directions. In that case the
passage will either be partitioned along its length, or a wooden box
laid through it to conduct one of the air currents. If one air course
crosses another, as is often the case, a channel will be cut in the
roof of one of the passages, and the lower side of the channel will be
closed tightly by masonry, to prevent any possible intermingling of the
currents, a circumstance which might prove disastrous. Entrances and
cross-headings cut through between parallel passages for purposes of
ventilation are closed as soon as the next cross-heading is made, for
reasons already explained. This closing is usually done by building up
in the aperture a wall of slate, rock, and coal, and filling the chinks
with dirt from the floor of the mine. Sometimes wooden partitions are
put in instead, and between principal air passages the cross-headings
are closed by heavy walls of masonry. When it is necessary to turn the
air from any traveling way, or to prevent it from further following
such traveling way, a partition is built across the passage, and in
the opening left in the partition a door is swung. If this is across a
way through which mine cars pass, a boy will be stationed at the door
to open it when the cars come and close it as soon as they have gone
through. He is called a “door boy.” All doors are so hung as to swing
open against the current of air, and are therefore self-closing. The
law directs that this shall be done. There are several patented devices
for giving an automatic movement to mine doors; but few if any of them
are in practical operation in the anthracite mines. The conditions here
are not favorable for the use of self-acting doors, and besides this
the act of 1885 provides that all main doors shall have an attendant.
The law is very explicit on this subject of ventilation; it is a matter
of the utmost importance in operating a mine. A failure of the air
current for even an hour might, in some mines, result in the death of
all those who chanced to be inside. For this current not only supplies
air for breathing purposes, but it takes up the smoke, the dust, the
dangerous and the poisonous gases, and carries them to the surface.
In the same way pure air is drawn into the lungs, loaded with the
refuse matter brought there by the blood, and then expelled. So life is
preserved in both cases.
In order to create this circulation of air and make it continuous,
artificial means are ordinarily used. The earliest method of creating
an artificial air current which should be constant, and one still
in use to a limited extent, is that by the open furnace. This is an
ordinary fireplace with grate bars, built near the foot of an opening
into the mine, and having a bricked-in smoke-flue which leads into the
air passage of that opening at some little distance above the floor of
the mine. The volume of heat thus passing into the airway will rarefy
the air therein, and so create and maintain a strong, invariable,
upward current. Sometimes the furnace is placed at the foot of an air
shaft a long distance from the main opening, thus making it an upcast
shaft. The reverse, however, is usually the case. All air that enters
the mine by any opening is usually drawn out at the main shaft or other
main entrance. But as the air returning from the working places of
the mine is often laden with inflammable gases, it is not allowed to
come into contact with the fire of the furnace, but is carried into
the shaft by a channel cut into the rock above the roof of the mine.
Furnace ventilation in mines in which explosive gases are generated is
dangerous at the best, and is now prohibited by the act of 1885.
The modern and most common method of creating and maintaining a
circulation of air in a mine is by a fan built at the mouth of the air
compartment of the shaft or slope. The fan exhausts the air from the
mine by the airway, and fresh air rushes in by the carriage way, or
any other opening to the surface to restore the equilibrium. Sometimes
the fan is used as a blower and forces air into the mine instead of
exhausting it. The advantage of this method is that it gives better air
to the workmen at the faces of chambers and headings, but the objection
to it is that it brings all the smoke and gases out by the main
gangway. This is a serious objection, not only making this principal
passage unfit to see or breathe in, but making it dangerous also by the
presence of inflammable gases. The fan is therefore commonly used as an
exhauster.
There are various kinds of fans in use at the mines, but the kind
generally employed is patterned after Guibal’s invention. It is simply
a great wheel without a rim, and instead of spokes it has blades
like those of a windmill. It is run by a steam-engine, makes forty
revolutions per minute at an average rate of speed, and sends from one
hundred thousand to two hundred thousand cubic feet of fresh air per
minute into the mine.
The act of 1885 requires the mine operator to furnish two hundred cubic
feet of air per minute to every man in the mine. This is the maximum
amount necessary for perfect respiration. In the larger workings
perhaps six hundred men and boys are employed. For this number one
hundred and twenty thousand cubic feet of air per minute would be
required by law. A large fan would supply this amount by running at
almost its minimum rate of speed. So long, therefore, as the fan and
air passages are in good working condition there need be no fear of
lack of proper ventilation. But to give absolutely pure air to the
workers in the mine is an utter impossibility under any system that has
yet been devised. The outer atmosphere that is drawn into the mines
has hardly got beyond the light of the sun before it has taken up a
certain percentage of impurities. As it passes by the working faces
of the chambers it carries along with it the gases evolved from the
coal; principally the carbonic acid gas or black damp, and the light
carbureted hydrogen or fire damp. It also takes up and carries along
the powder smoke, the organic matter contained in the exhalations of
men and animals, the products of decaying timber, and the dust which
is always in the air. Nor is this the only deterioration which this
air current undergoes. The proportion of oxygen in it is diminished by
the burning of many lamps, by the respiration of many men, and by the
constant decay of wood. It is seen, therefore, that the air in which
the miner must breathe is far from being the pure oxygen and nitrogen
of the outside atmosphere. It follows also that the longer the route is
of any particular current, and the more working faces it passes in its
course, the more heavily laden will it be with impurities, and the more
poisonous for those men who last breathe it on its return to the upcast
air shaft.
This evil, however, is limited in extent by the act of 1885, which
provides that no more than seventy-five persons shall be employed at
the same time in any one split or current of air.
The wonder is that the health of these mine workers does not sooner
fail them, especially when we take into consideration the wet condition
of many of the mines. It is a fact, however, that miners as a class are
not more subject to disease than other workmen. The decimation in their
ranks is due mostly to accidents producing bodily injuries and death,
not to diseases which attack them as a result of their occupation.
Next in importance to the matter of ventilation in mines is the matter
of drainage. The first difficulty experienced from water is while the
shaft or slope is in process of sinking. It is usually necessary to
hold the water in one side of the opening while work is going on in
the other side. A small pumping engine is generally sufficient to keep
the pit clear until the bottom is reached, but occasionally the amount
of water is such that a large engine and pumping appliances have to be
put in place at once. In Europe much trouble is often experienced from
the excessive flow of water while sinking the shaft, and a watertight
casing has frequently to follow the shaft downward in order that work
may go on at all. Such appliances are not as a rule necessary in this
country, though much difficulty has been encountered in sinking shafts
through the quicksand deposits of the Susquehanna basin in the Wyoming
valley.
The general principle of mine drainage has been already explained. It
is, in brief, that the floor of the mine shall be so graded that all
water will gravitate to a certain point. That point is near the foot
of the shaft or slope, and is at the mouth of the drift or tunnel.
But from the sump of the shaft or slope the water must be raised by
artificial means. A powerful steam pumping engine, located at the
surface, is employed to do this work, and one compartment of the shaft
or slope, known as the pump-way, is set aside for the accommodation
of pipe, pump-rods, and supporting timbers, which extend from the top
to the bottom of the shaft. The most powerful of these pumps will
throw out a volume of twelve hundred gallons of water per minute. It
is seldom that the tonnage of water pumped from a mine falls below
the tonnage of coal hoisted, and in some of the wet collieries of the
Lehigh district eight or ten tons of water are pumped out for every ton
of coal hoisted. In the Wyoming district a thousand tons of water a day
is not an unusual amount to be thrown out of a mine by a single pump.
In driving gangways or chambers toward abandoned workings that have
been allowed to fill with water much care is necessary, especially if
the new mine is on a lower level, which is usually the case. The act of
1885 provides that “whenever a place is likely to contain a dangerous
accumulation of water, the working approaching such place shall not
exceed twelve feet in width, and there shall constantly be kept, at a
distance of not less than twenty feet in advance, at least one bore
hole near the centre of the working, and sufficient flank bore holes on
each side.” It often happened, before accurate surveys of mines were
required to be made and filed, that operators would drive chambers
or gangways toward these reservoirs of water in ignorance of their
whereabouts. The firing of a blast, the blow of a pick, perhaps, would
so weaken the barrier pillar that it would give way and the water
breaking through would sweep into the lower workings with irresistible
force, carrying death to the workmen in its path and destruction to the
mine. Some very distressing accidents have occurred in this way. It
is customary now for operators, when approaching with their workings
a boundary line of property, to leave a barrier pillar at least one
hundred feet thick between that line and the outer rib or face of their
workings; and this whether the area on the other side of the line is
or is not worked out. Under the present system of accurate surveying
and mapping, accidents resulting from flooding by mine water should be
rare, since the location of boundary lines may be calculated almost to
the inch, as well as the location of all workings in their relation to
each other.
But accidents due to a flooding by surface water are not always to
be obviated. Sometimes when a stream crosses the line of outcrop the
water will break through into the mine and flood the lower levels in
an incredibly short space of time; and this too when good judgment and
prudence have been used in leaving sufficient coal for protection.
The continuity and character of the strata lying between the earth’s
surface and the coal face cannot always be determined. It is not often
that accidents from flooding occur while mining is going on under large
bodies of water. The precautionary measures taken in presence of a
known danger are sufficient to reduce that danger to a minimum.
Disasters occur occasionally as the result of a peculiarly deceptive
condition of the overlying strata, whereby a rush of earth, quicksand,
or mud into a mine causes loss of life and destruction of property.
The bed of a stream cut deep into the rocks in some former geological
period, and then filled to the level of the surrounding country
with drift in some later age, leaves a dangerous and unsuspected
depression in the strata which the miner’s drill may pierce or his
blast break into at any time with disastrous results. One of the most
characteristic of this class of accidents occurred at Nanticoke in
the Wyoming region on the 18th of December, 1885, in a mine operated
by the Susquehanna Coal Company. A miner by the name of Kiveler broke
into a depression of this kind while blasting, and immediately through
the aperture a great volume of water, quicksand, and culm came rushing
down. It filled up that entire portion of the mine, burying twenty-six
men and boys beyond possible hope of rescue and endangering the lives
of hundreds of others. Energetic efforts were made to tunnel through
the masses of sand and culm packed in the passages of the mine in
order to reach those whose avenues of escape had been cut off, many
believing that they had been able to reach high enough ground to escape
the flood. These efforts, lasting through many weeks, were wholly
unsuccessful. The men were never reached. Bore holes, drilled into the
chambers where they were imprisoned, both from the inside and from the
surface, proved conclusively that the passages were crowded full of
sand and culm, and that the men must have perished immediately upon the
occurrence of the disaster.