A 480,000-ton anthracite coal storage plant. Coal cars are dumped into
hoppers under the tracks and the coal carried to the top of the piles by
conveyors. It is reloaded into cars by other conveyors operating at the
base of each pile. This system has been of great value in preventing a
shortage of coal during strikes.]
Consequently a plan has been evolved for the ventilating current to be
reversed periodically, in order to remove dust which has settled on the
side of timbering and crevices, and the roadways to be watered in order
to allay the dust. A plan has also been tried of spreading fine
stone-dust in the roadways. This mixes with the coal-dust and renders it
less inflammable.
Unfortunately the disastrous effects of an explosion do not end with the
explosion itself. The main products of combustion, whether of fire-damp
or coal-dust, are carbon monoxide and carbon dioxide. The latter causes
suffocation and the former is a dangerous poison. It is the dreaded
“after-damp” of the miner. Those who survive an explosion are therefore
in danger of suffocation or poisoning, and it becomes imperative to
restore the circulation of the air with the least possible delay. For
even if the fan has escaped injury, fallen portions of the roof may have
choked up some of the roadways, or the explosion may have torn down
doorways and provided a short cut for the air. But if the atmosphere is
dangerous for men in the pit at the time, it is equally dangerous for
others to go down and effect repairs or render first aid.
The work of the rescue party is therefore a labor of desperate heroism
and often attended by additional loss of life. It has recently been
found possible to reduce the dangers of after-damp by providing rescue
parties with respirators fitting over the mouth and nose, and supplied
with oxygen from two steel bottles of the compressed gas strapped across
the back. An effective apparatus of this kind, such as has been adopted
by the United States Government for the use of the Bureau of Mines
Rescue Crew, is shown in the accompanying illustration. The bag in front
is known as a “breathing bag” and has separate compartments for the
inhaling and exhaling, the tube at the right leading to the former and
that at the left to the exhaling compartment, which usually contains
sticks of caustic soda to absorb the carbon dioxide exhaled by the
wearer.
Coal is largely formed from vast masses of vegetable matter deposited
through the luxuriant growth of plants in former epochs of the earth’s
history. In the varieties of coal in common use the combined effects of
pressure, heat and chemical action upon the substance have left few
traces of its vegetable origin; but in the sandstones, clays and shales
accompanying the coal the plants to which it principally owes its origin
are presented in a fossil state in great profusion and frequently with
their structure so distinctly retained, although replaced by mineral
substances, as to enable the microscopist to determine their botanical
affinities with existing species. Trees of considerable magnitude have
also been brought to light.
[Illustration: SECTION OF PART OF A COAL-FIELD, SHOWING A SUCCESSION OF
BURIED TREES AND LAND SURFACE
_a_, sandstones.
_b_, shales.
_c_, coal-seams.
_d_, under-clays or soils.]
The animal remains found in the coal-measures indicate that some of the
rocks have been deposited in fresh water, probably in lakes, while
others are obviously of estuarine origin, or have been deposited at the
mouths of rivers alternately occupied by fresh and salt water. The great
system of strata in which coal is chiefly found is known as the
carboniferous.
[Illustration: MINE SAFETY CREW]
[Illustration: MINE RESCUE WORK
Upper view, Bureau of Mines Rescue Crew in safety helmets, ready to
enter a gas-filled mine. Lower view, resuscitating a victim overcome by
gas by means of the oxygen reviving apparatus.]
[Illustration: BRIQUETTING MACHINE
Enormous quantities of coal are lost at the mines in coal dust. By
adding a binding material, such as pitch, and pressing the mixture into
briquettes or small bricks, an excellent fuel is made.]
[Illustration: MINE RESCUE WORK
The mine rescue crew is using the canary-bird test for poisonous gas.
The bird succumbs to gas earlier than a man and thus indicates a
dangerous condition of the atmosphere. The canary is revived by oxygen
and the crew puts on safety helmets before proceeding.]
There are many varieties of coal, varying considerably in their
composition, as anthracite, nearly pure carbon, and burning with little
flame, much used for furnaces and malt kilns; bituminous, a softer and
more free-burning variety; and cannel or “gas-coal,” which burns readily
like a candle, and is much used in gasmaking. The terms semi-anthracite,
semi-bituminous, coking coal, splint coal, etc., are also applied
according to peculiarities.
All varieties agree in containing from 60 to over 90 per cent of carbon,
the other elements being chiefly oxygen and hydrogen, and frequently a
small portion of nitrogen. Lignite or brown coal may contain only 50 per
cent of carbon. For manufacturing purposes coals are generally
considered to consist of two parts, the volatile or bituminous portion,
which yields the gas used for lighting, and the substance, comparatively
fixed, usually known as coke, which is obtained by heating the coals in
ovens or other close arrangements.
About 260,000,000 tons of coal are annually mined in Britain, the value
being over $300,000,000. Large quantities are exported. The British
coal-fields, though comparatively extensive (covering about 9,000 square
miles), are far surpassed by those of several other countries, as the
United States and China, the former having coal-fields estimated to
cover about 451,000 square miles; the latter over 200,000 square miles.
Britain no longer mines the largest quantity, having been far surpassed
by the United States. Other countries in which coal is worked are
Belgium, France, Germany, Russia, India, New South Wales and Canada.
China has hitherto mined only on a small scale.
The annual production of anthracite coal in Pennsylvania is more than
86,000,000 tons of 2,240 pounds, valued at the mines at $198,000,000. In
1910 there were produced of bituminous coal 388,222,868 tons, valued at
$463,654,776; amount of coke manufactured, 37,000,000 tons. This was
distributed widely over the country, the greatest producers, after
Pennsylvania, being Illinois, West Virginia, Ohio, Alabama and Colorado.
Recently a very large output of coal has been discovered in Alaska, the
value of which is as yet undetermined, though it is believed to hold a
vast quantity of coal. The value of the western coal-fields also is far
from known, and since 1906 very extensive tracts of coal-bearing lands
have been withdrawn from settlement, principally in Wyoming, Montana,
Colorado, Utah and New Mexico, their beds being largely of lignite.
These cover about 50,000,000 acres, and, with those of Alaska, are held
by the government as national assets. The mines of Alaska are claimed to
be exceedingly rich, both in bituminous and anthracite coal, the beds
examined being estimated to contain 15,000,000,000 tons, while there are
large districts unexamined. They have not yet been worked, the
government keeping them back for public ownership.
* * * * *
How can We Hear through the Walls of a Room?
We are able to hear easily through the walls of many rooms because the
material used in those walls are good conductors of sound. We know that
some things are better conductors of heat than others, and just in that
same way, some things conduct sound better than others. Wood has been
shown to be an even better conductor of sound than air. Most of us have
stood at the foot of an overhead trolley pole to see if we could hear a
car coming, and we know that the reason we did this was because we could
hear the wire humming, when we put our ears against the pole, even
though we could not hear any sound in the air.
When we are in a room that has wooden walls we can hear sounds in the
next room very plainly, not because the wall is thin, but because the
wood in the wall is a good conductor of sound. Other walls made of
different kinds of material, are not as good conductors of sound. While
you may hear through them, you cannot hear as plainly as you can through
a wooden wall.
What is a Diesel Engine Like?
The Diesel engine has caused a great deal of comment of late years
because of the spectacular uses to which it has been successfully
applied. A specially constructed Diesel engine was probably the chief
aid in the accomplishment of the first submarine trans-Atlantic voyage
by the German submarine “Deutschland.”
It is an oil engine which was invented by Rudolph Diesel in 1893.
The engine operates at compression pressures very much higher than those
used in any other internal combustion engines, and it dispenses with the
usual igniting devices by rendering the air charge incandescent by
compression.
[Illustration: THE DIESEL ENGINE]
The efficiency of the Diesel engine is high, and it can use low grades
of fuel, but it has the disadvantage of greater weight per horse-power
than other engines.
It has found increasing favor for use in marine propulsion, and in 1913
was adapted to high-speed railway service, and put into use in Germany.
What does the Sheep-Grower Get for the Wool in a Suit of Clothes?
A man’s ordinary three-piece fall suit has about nine pounds of wool in
it. Such a suit might cost somewhere between twenty and forty dollars,
depending on whether it was bought ready made or whether it was made to
order. If the price was questioned, the retailer would probably explain
that it was all wool and that the wool cost was the reason it was
expensive, and still the sheep-man who raised the wool only received an
average of about eighteen cents a pound, or $1.62, for all the wool used
on the suit.
Of course, the largest part of the cost of a suit of clothes is really
accounted for by the cost of transportation, weaving, tailoring and
selling, but we must all agree that the sheep-man who tends the flock
all winter and cuts the wool in the spring is not to blame for high
prices.