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                    THE MENTOR 1918.05.01, No. 154,
                            The Story of Coal




                            LEARN ONE THING
                               EVERY DAY

                    MAY 1 1918       SERIAL NO. 154

                                  THE
                                MENTOR

                             THE STORY OF
                                 COAL

                                  By
                        CHARLES FITZHUGH TALMAN

                       Editorial Writer for the
                          Scientific American

                      DEPARTMENT OF      VOLUME 6
                      SCIENCE            NUMBER 6

                          TWENTY CENTS A COPY




THE MINER

By BERTON BRALEY


    Grimy, and caked with dust of coal he stands,
    Grasping his pick within his mighty hands;
    The arbiter of destiny and fate,
    Greater by far than king or potentate.

    Shops may not run except at his behest,
    At forge and blast his strength is manifest.
    The rolls that rumble and the shears that scream
    And all the million miracles of steam

    Depend on him for fuel that will turn
    The wheels that urge them and the belts that churn.
    Guns that will shatter fortresses of steel,
    Ships that will plow the waves on steady keel

    Bearing munitions for an army’s need
    Must wait the miner’s orders and take heed
    That he who toils within the coal mine’s murk
    Gives them the coal with which they do their work.

    Behind the men who battle in the trench
    There stand the workmen at the lathe and bench,
    But back of them and master of them all
    The miner stands and holds the world in thrall.

    Not soon again shall any man forget
    How much the world is in the miner’s debt,
    For we shall read upon fame’s honor roll
    “He won the war--his labor gave us coal!”

Reprinted by courtesy of Publishers of “Coal Age.”




[Illustration: COURTESY U. S. GEOLOGICAL SURVEY

FOSSIL FERN FROM COAL MINE]




_THE STORY OF COAL_

_The Origin of Coal_

ONE


While the vegetable origin of coal is beyond question, two rival views
are current among geologists to account for the deposit of ancient
plant material in the form of coal-beds, such as we now find in the
earth. One school of geologists holds that the coal plants grew in
great lagoons and swamps, like the mangrove swamps of today, and that
the modern coal-beds mark the locations of these swamps. From time to
time these areas subsided and were flooded with water to such a depth
that the plants were killed. Eventually the decayed vegetation of the
former swamps was covered with a layer of mud or sand. Later a slow
upheaval of the ground brought these regions again to the surface; a
new swamp formed, only to be submerged again at a later period; and the
same process was repeated several times in the course of hundreds of
thousands of years.

The bulk of evidence seems to favor this view, but there is another.
Perhaps the coal-beds are not the sites of former swamps, but of
estuaries and ocean shores where the plant material settled down,
in still water, after a long drift down the ancient rivers from its
place of origin. It is not impossible that both explanations are
correct; some coal-beds having been formed in one way, and some in the
other. With the progress of time the deposits of sand were compacted
into sandstone, and the mud and clay into shale; while the layers of
vegetation were solidified by pressure, some of their constituents were
vaporized and expelled by heat, and the final product was coal.

The coal-measures abound in fossil plants of species long ago extinct,
and we also find the molds or casts of plants that have themselves
disappeared, leaving only their impressions in the mud by which they
were once enveloped. These records of ancient vegetation are mostly
found in the rocks just above and below the coal-beds, and not in the
coal itself.

The plants of the Carboniferous Period, during which most but not all
of the coal-beds were formed, bore a family likeness to certain kinds
of plants that flourish today. Many of them were ferns, ranging in size
from the smallest species up to great tree-ferns. Others resembled our
modern horsetails or scouring-rushes, with their fluted and jointed
stems, but these _calamites_, as the geologists call them, grew to
the size of trees, sometimes eighty or ninety feet in height. Some
plants of the coal age were like the modern cycads (intermediate in
appearance between tree-ferns and palms); some were like the ginkgo, a
tree with leaves like those of maidenhair fern, widely introduced into
this country from China and Japan. One of the commonest and largest
trees was the _lepidodendron_, closely resembling, except in its vastly
greater size, the club-moss or ground pine which we know so well as a
Christmas decoration.

The animal life of the period, of which, also, abundant fossil remains
are found, included mollusks, fishes, crustaceans, insects, spiders,
thousand-legs, snails, reptiles and lizards. Some of the insects were a
foot or more in length. Of cockroaches, alone, more than five hundred
species have been found in the coal-measures.

    PREPARED BY THE EDITORIAL STAFF OF THE MENTOR ASSOCIATION
    ILLUSTRATION FOR THE MENTOR. VOL. 6, No. 6, SERIAL No. 154
    COPYRIGHT, 1918. BY THE MENTOR ASSOCIATION, INC.




[Illustration: COURTESY U. S. BUREAU OF MINES

TIPPLE AT BITUMINOUS COAL MINE GARY, WEST VIRGINIA]




_THE STORY OF COAL_

_The Coal Fields of the United States_

TWO


When a coal famine is upon us there is a grain of comfort in the
reflection that beneath the soil of this country, and within 3,000
feet of the surface, there still lies 3,538,554,000,000 tons of coal.
This is the estimate of the United States Geological Survey. We have
mined coal wastefully and used it prodigally, yet we have taken from
the ground, up to the present time, only a fraction of one per cent. of
the total amount at our disposal. The whole of our “coal reserves,” if
they could be extracted and placed in a great cubical pile, would form
a mass 8.4 miles long, 8.4 miles wide and 8.4 miles high. If the coal
thus far mined were piled up in the same way, the cube would be 7,200
feet long, 7,200 feet wide, and 7,200 feet high.[1]

    [1] These figures were furnished by Mr. M. R. Campbell, of the
    U. S. Geological Survey. They differ materially from figures
    previously published by the Survey.

The coal-producing areas of the country are divided into six great
divisions, known as the Eastern Province, the Interior Province, the
Gulf Province, the Northern Great Plains Province, the Rocky Mountain
Province, and the Pacific Coast Province. The Eastern Province
contains probably nine-tenths of the high-rank coal of the country.
It is made up of the anthracite regions of Pennsylvania and Rhode
Island, the Atlantic coast region of Virginia and North Carolina, and
the great Appalachian region, which embraces all the bituminous and
semi-bituminous coal of what is called the “Appalachian trough.” The
state of Pennsylvania produces 47 per cent. of all the coal mined in
the country, and nearly all of the anthracite.

The Appalachian region is the greatest storehouse of high-rank coal
in the United States, if not in the world. “This near-by and almost
inexhaustible supply of high-grade fuel,” says the Geological Survey,
“has been the foundation of the development of the blast furnaces, the
great iron and steel mills, and the countless manufacturing enterprises
of the Eastern states.”

The Interior Province includes all the bituminous coal fields and
regions near the Great Lakes, in the Mississippi Valley, and in Texas,
and is made up of four distinct sections--the northern (Michigan),
eastern (Illinois, Indiana and western Kentucky), western (Iowa,
Missouri, Kansas, Oklahoma and Arkansas), and southwestern (Texas). The
coal of this province is not, in general, of as high a quality as that
of the Eastern Province, but it is very extensively mined, and is used
for heating and for generating power in the many cities and towns of
the Mississippi valley and the Great Lakes region. Indeed, extensive
coal fields in proximity to rich agricultural lands have made possible
the existence of such manufacturing centers as Chicago, St. Louis and
Kansas City, and have been a leading factor in the development of the
vast railway systems of the Middle West.

The Gulf Province is at present of little commercial importance. Its
coal is mined only at a few places in Texas, and is mostly lignite.

The Northern Great Plains Province includes all the coal fields in the
Great Plains east of the Front Range of the Rocky Mountains. The coals
are of low rank, being either lignite or sub-bituminous, except in a
few of the basins near the mountains. The largest coal region in this
province is the Fort Union region, lying in the Dakotas, Montana and
Wyoming. The amount of unmined coal in this region is estimated to be
twice as great as that lying in the rich Appalachian region, but it has
been little worked, as it is generally of poor quality.

The Rocky Mountain Province contains a greater variety of coal than
any other province in the United States. It includes all ranks, from
lignite to anthracite, but the prevailing ranks are sub-bituminous and
low-grade bituminous.

The coal of the Pacific Coast Province is mined chiefly in the state
of Washington, where it has aided in developing the industries of the
Puget Sound region. Oregon and California have small fields, but the
coal is of poor quality, and little mining has been attempted.

    PREPARED BY THE EDITORIAL STAFF OF THE MENTOR ASSOCIATION
    ILLUSTRATION FOR THE MENTOR. VOL. 6, No. 6, SERIAL No. 154
    COPYRIGHT, 1918. BY THE MENTOR ASSOCIATION, INC.




[Illustration: COURTESY BROWN HOISTING MACHINERY CO. CLEVELAND, O.

COAL CAR DUMPER IN OPERATION]




_THE STORY OF COAL_

_Handling Coal_

THREE


In times gone by coal was carried out of the mines on the shoulders
of men and women, and then transferred in wheelbarrows to the
sailing-vessels or wagons in which it was taken to market. In
progressive mines of today the coal is loaded in the mine into small
mine cars, which are hauled and hoisted to the surface by electricity
or steam. The mine cars are dumped on an elevated platform called
the “tipple,” and the coal passes through chutes or conveyors to the
railway cars waiting underneath to receive it. On its way downward it
undergoes a more or less elaborate process of screening, breaking,
picking, washing, etc., according to the kind of coal and the purpose
for which it is to be used.

The coal reaches the market by three general methods of transportation:
(1) All-rail; (2) rail to the seaports, where it is used for bunkering
steamers or carried by vessels to other ports, foreign and domestic;
(3) rail to the Great Lakes, especially Lake Erie ports, from which
it is carried to ports on the upper lakes, and from the latter again
by rail to markets in the interior. The railroads themselves use
about one-fourth of all the coal mined in this country. The coastwise
coal-carrying trade is mainly by wooden barges towed by steamers,
though much coal is also carried by schooners, some of which can carry
a cargo of 5,000 tons or more. About four per cent. of the bituminous
coal output goes to foreign countries.

“The consumption of coal,” says the United States Geological Survey,
“is a measure of the industrial activity of a people, for as yet coal
is the main source of mechanical energy. In this respect the United
States is the foremost nation, its average annual consumption of coal
for all purposes being about five tons per capita. Prior to the present
war in Europe the consumption of coal per capita in England, Belgium
and Germany was about four tons, in Russia a quarter of a ton, and in
France about 1.6 tons.”

Marvelous forms of labor-saving machinery have been introduced to
facilitate the loading and unloading of coal. The principal form of
apparatus for transferring coal either to or from a vessel is the
“bridge tramway plant,” which consists of long steel bridges mounted
side by side on suitable rails so that they can be moved into place
over the hatchway of a vessel. Huge buckets, which load and unload
themselves, are carried on a “trolley,” suspended from the bridge,
and transfer coal at high speed from the vessel to the stock pile or
railway cars, or _vice versa_. The cost of loading coal by this method
is only a cent or two a ton.

Another ingenious device is the “car-dumper.” This powerful machine
picks up bodily from the railway track a car loaded with a hundred tons
of coal, overturns it, and discharges its contents into the hold of a
vessel; after which it returns the car to the track. It is capable of
handling fifty cars an hour. It is equipped with special apparatus to
prevent the coal from being discharged too violently, and thus being
badly broken up.

    PREPARED BY THE EDITORIAL STAFF OF THE MENTOR ASSOCIATION
    ILLUSTRATION FOR THE MENTOR. VOL. 6, No. 6, SERIAL No. 154
    COPYRIGHT, 1918. BY THE MENTOR ASSOCIATION, INC.




[Illustration: COURTESY POPULAR SCIENCE MONTHLY

CHARGING COAL IN A MODERN GAS PLANT]




_THE STORY OF COAL_

_Coal Products_

FOUR


The story of the coal products forms one of the most romantic chapters
in the history of applied science. The marvels of fairyland are
surpassed by the achievements of the modern manufacturer in obtaining
from mere black rocks dug out of the ground not only heat and light,
but a bewildering variety of useful gases, liquids and solids--drugs,
chemicals, dyestuffs, and so forth.

For hundreds of years it has been known that when coal is covered
or enclosed, to keep out the air, and then heated for a certain
length of time, instead of burning to ash it is converted into a
porous grayish-black substance called “coke.” This material, which
burns without smoke or flame, is a valuable fuel for many purposes;
especially for use in blast-furnaces for the smelting of ore. Nowadays
coke is made on a vast scale from certain grades of bituminous and
semi-bituminous coal. The coal is heated in “coking-ovens,” of which
there are several kinds. The most common form of oven in this country
is the “bee-hive oven,” which produces coke only. Another type of
coking-oven, more generally used in Europe than in America, is the
“flue-oven,” which produces, besides coke, a number of valuable
by-products.

When coal is converted into coke it gives off combustible gases. The
idea of saving these gases and using them for illuminating purposes
was first practically applied in the latter part of the eighteenth
century. “Coal-gas” is made by heating coal in a closed vessel, called
a “retort.” It is a mixture of hydrogen and methane (a compound of
hydrogen and carbon), with small amounts of several other gases. Most
of the carbon in the coal remains in the retort as coke, which is,
therefore, a by-product in the process of making coal-gas. After the
gas is given off from the coal it passes through a series of vessels,
where, by chemical and other methods, it is freed from ingredients
which would impair its value as an illuminant, but which are saved and
used for other purposes; the most important of these are “coal-tar”
and “ammoniacal liquor.” The purified coal-gas is finally conveyed
to a gas-holder or “gasometer,” from which it is distributed to the
consumers.

In recent times other methods of gas-making have come into use. In one
of these nearly all the carbon in the fuel is turned into a combustible
gas by passing air through the hot coal. The product is known as
“producer-gas,” and is very valuable for use as fuel and as a motive
power in gas-engines, but it is not an illuminant. A modification of
this process, in which steam is passed over the heated fuel, gives
a mixture of hydrogen and carbon monoxide, known as “water-gas.”
This is also a valuable source of heat and power; but for use as an
illuminant it must be mixed with a gas made from oil. It is then known
as “carburetted water-gas,” and is very extensively used for lighting
purposes; either by itself or mixed with ordinary coal-gas.

Of the by-products of gas-making, ammoniacal liquor was, until
recently, the only commercial source of ammonia. Coal-tar, formerly
thrown away as worthless, is today the source of innumerable substances
of immense value to science and the industries. From coal-tar are
obtained benzine, toluene, xylene, phenol (carbolic acid), naphthalene,
anthracene, etc., and these more direct products are combined with
one another or with other chemicals to produce coloring matters,
explosives, perfumes, flavoring materials, sweetening substances,
disinfectants, medicines, photographic developers--in short, a little
of everything. The total number of coal-tar products runs into the
thousands, and is constantly being increased by fresh discoveries.

In Germany, just before the war, the industries engaged in making these
products (no longer _by_-products, but far more important than coke and
gas) were capitalized at $750,000,000. One firm made no less than 1,800
coal-tar dyes, besides 120 pharmaceutical and photographic preparations.

    PREPARED BY THE EDITORIAL STAFF OF THE MENTOR ASSOCIATION
    ILLUSTRATION FOR THE MENTOR. VOL. 6, No. 6, SERIAL No. 154
    COPYRIGHT, 1918. BY THE MENTOR ASSOCIATION, INC.




[Illustration: SMOKE PROBLEM--SCENE IN PITTSBURGH BEFORE AND AFTER THE
SMOKE CURE]




_THE STORY OF COAL_

_The Smoke Problem_

FIVE


Smoking is a costly and injurious habit. This is not the beginning of
an appeal on behalf of the anti-cigarette crusade, but the introduction
to a few facts in regard to the far-reaching effects of smoky chimneys.
The smoke nuisance is as old as the use of coal. In the fourteenth
century a man was executed in London for befouling the air of that
city with the fumes of “sea-coal,” as ordinary mineral coal was once
called in England, because it was brought to London by sea. Under
Queen Elizabeth a law was passed forbidding the burning of coal while
Parliament was in session, as the legislators believed their health was
likely to be impaired by the smoky air of the city. What would these
bygone gentlemen say if they could see modern London enveloped in one
of its famous “pea-soup” fogs--the color and denseness of which are
entirely due to coal-smoke?

Smoke is injurious to health, destructive to vegetation, and fatal
to architectural beauty; and, along with all this, it is enormously
expensive. In the first place, a smoky chimney means imperfect
combustion, and a waste of part of the heating value of fuel. Then a
smoky atmosphere entails big laundry and dry-cleaning bills; frequent
repainting of houses; injury to metal work; damage to goods in shops;
excessive artificial lighting in the daytime. Pittsburgh was once
the most famous American example of all these evils, but it has
recently reformed. Before the Mellon Institute of Industrial Research
carried out its elaborate smoke investigation in that city, and, in
consequence, stringent smoke-abatement ordinances were adopted, the
annual smoke bill of Pittsburgh was estimated at nearly ten million
dollars. The city was the paradise of the laundryman, and light-colored
clothing was so little worn by the inhabitants that it was known as
“the mourning town.”

Throughout the United States it is said that smoke causes an annual
waste and damage amounting to half a billion dollars. No wonder
numerous societies have been formed to mitigate this evil, and a great
many laws have been enacted on the subject. With a gradual increase in
the use of gas, coke and other smokeless fuels, and improved methods of
stoking furnaces, the smoke nuisance is now happily abating.

The pollution of the air by smoke is the subject of systematic
investigation and measurement at certain places in this country and
abroad. Measurements of the “soot-fall” made in Pittsburgh a few years
ago indicated an annual average deposit of soot in that city amounting
to 1,031 tons per square mile. London’s average is 248 tons per square
mile for the whole city and 426 tons in the central districts. In the
heart of Glasgow the annual soot-fall is 820 tons per square mile.

In Great Britain there is a Committee for the Investigation of
Atmospheric Pollution, which has installed standard measuring apparatus
in sixteen English and Scotch towns. The soot is collected in a
“pollution gauge,” consisting of a large cast-iron funnel, enameled
on the inside. Projecting above the gauge is a wire screen, open at
the top, to prevent birds from settling on the edge of the vessel.
The gauge communicates at the bottom with one or more bottles for
collecting rain-water, with its solid contents. The bottles are emptied
once a month, when their contents are weighed and analyzed.

Smoke is injurious to the respiratory organs, conducive to eye-strain
and responsible for a lowering of human vitality. The gloominess of a
smoke-laden atmosphere also has a depressing effect upon the minds of
many people.

    PREPARED BY THE EDITORIAL STAFF OF THE MENTOR ASSOCIATION
    ILLUSTRATION FOR THE MENTOR. VOL. 6, No. 6, SERIAL No. 154
    COPYRIGHT, 1918. BY THE MENTOR ASSOCIATION, INC.




[Illustration: COURTESY U. S. BUREAU OF MINES

RESCUE PARTY ENTERING MINE AFTER EXPLOSION]




_THE STORY OF COAL_

_Safety in Coal Mines_

SIX


Since the year 1870, some 60,000 men have lost their lives as a result
of coal mining accidents in this country. This is approximately one
fatality for every 180,000 tons of coal mined. Gradually this bad
record is being improved, thanks to the combined efforts of the United
States Bureau of Mines, the mining departments of the various states,
the operators and the miners themselves; but coal mining remains a
hazardous pursuit.

Falls of the roof are responsible for more accidents than any other
single cause. These are likely to occur wherever the roof is not fully
timbered; especially in the “rooms,” where the coal is being blasted
out. Many accidents also occur in mine shafts, notwithstanding the
various safety devices with which the “cage” or elevator is nowadays
provided.

Fires and explosions attract a greater amount of public attention than
other mining disasters on account of the large number of victims so
often involved in a single occurrence of this kind. In the explosion
at the Courrières colliery, in France, March 10, 1906, more than
1,100 miners perished. This mine had previously been renowned for its
freedom from accidents. Coal mine explosions are due to two principal
causes, which may act either separately or in combination--fire-damp
and coal-dust. Accumulations of fire-damp, or methane, locked up in
the coal seams, are liberated by the removal of the coal. Frequently
streams of this gas gush forth with a hissing noise, and are known
as “blowers.” Fire-damp is explosive when combined with certain
proportions of air. Apart from ventilation, which dilutes the gas below
the danger limit, the principal precaution against explosives is the
use of safety-lamps, so constructed that the gas cannot come in contact
with a naked flame. An excessive amount of coal-dust in the air of the
mine may also give rise to explosions. Such explosions may be prevented
by wetting the dust, moistening the air, or powdering the walls, roof
and floor with a non-explosive “rock-dust.”

After an explosion the air of a mine contains a large amount of the
deadly gas carbon monoxide, and this “after-damp,” as it is called,
makes rescue work extremely dangerous. Wherever suitable apparatus
is available, the rescuers carry with them a supply of oxygen, by
breathing which they are able to live for some hours in a poisonous
atmosphere. The Bureau of Mines has established a number of rescue
stations in the coal-mining districts and maintains several mine
safety cars for hurrying rescue crews to the scene of a disaster. The
Bureau also instructs the miners in first-aid and rescue work, and is
directing a national campaign in behalf of “safety first” in mines.

Of the many methods that have been devised for testing the air of
mines for noxious gases none is more interesting than the use of caged
canaries. These birds are much more susceptible than human beings to
the effects of carbon monoxide, and show signs of distress before a
man begins to feel any discomfort from the gas. In many mines they
are carried in routine inspections. After an explosion the number of
rescuers equipped with oxygen apparatus is always limited. These form
the advance guard, and are followed by men without apparatus, who
carry canaries, by observing the behavior of which they can tell how
far they may safely penetrate into the mine. The Bureau of Mines has
devised a special form of cage in which the canary may be revived with
oxygen after being overcome with gas. Experiments show that the bird
may be asphyxiated and revived again and again without suffering any
ill-effects; neither does he acquire an immunity to poisoning which
would make him a less reliable indicator.

    PREPARED BY THE EDITORIAL STAFF OF THE MENTOR ASSOCIATION
    ILLUSTRATION FOR THE MENTOR. VOL. 6, No. 6, SERIAL No. 154
    COPYRIGHT, 1918. BY THE MENTOR ASSOCIATION, INC.




THE MENTOR · DEPARTMENT OF SCIENCE

MAY 1, 1918

[Illustration: Courtesy of Brown Hoisting Machinery Co.

COAL-HANDLING MACHINERY ON PITTSBURGH COAL CO. DOCKS, DULUTH, MINN.

An electric trolley, with 5½-ton bucket, travels on each bridge,
carrying coal from the boat to storage, or to railroad car, or to
screening apparatus in the rear]

THE STORY OF COAL

By CHARLES FITZHUGH TALMAN

_Editorial Writer for the Scientific American_

_MENTOR GRAVURES_

FOSSIL FERN FROM COAL MINE · TIPPLE AT BITUMINOUS COAL MINE · COAL
CAR DUMPER IN OPERATION · CHARGING COAL IN A MODERN GAS PLANT · SMOKE
PROBLEM, SCENE IN PITTSBURGH BEFORE AND AFTER SMOKE CURE · RESCUE PARTY
ENTERING MINE AFTER EXPLOSION

Entered as second-class matter March 10, 1913, at the postoffice at New
York, N. Y., under the act of March 3, 1879. Copyright, 1913, by The
Mentor Association, Inc.


Were it possible for the lump of coal that we burn in our stove, grate
or furnace to tell its story, it would take us back millions of years
to a time when vast areas of the earth’s surface were covered with
swamps, supporting a luxuriant vegetation. No human being, mammal
or bird yet existed. Animal life included fish, shellfish and other
aquatic species, besides reptiles and insects. The vegetal forms
resembled our modern ferns, horsetails, club-mosses and evergreens.
The atmosphere was heavily charged with moisture, and a mild climate
prevailed even in the polar regions. Such were the conditions under
which, during the great Carboniferous Age, most of the existing
coal-beds were deposited in the earth.

[Illustration: FOREST SWAMP OF THE CARBONIFEROUS PERIOD (Coal Age).

From a drawing by Potonié and Gothan]

Coal is the litter of primeval swamps and forests. Year after year the
débris of the humid jungles accumulated in shallow water or in the
boggy soil, where it underwent partial decay, and was thus converted,
first of all, into the slimy or spongy material known as “peat.”
Similar deposits are in process of formation in the swamps of the
present day, and the peat obtained from them is dried and used as fuel
on an extensive scale in some parts of the world; especially Ireland,
Holland, Germany and Scandinavia.

[Illustration: CONCRETE PORTAL OF A “DRIFT” MINE]

Gradual changes in the elevation of the land led to the submergence
of the prehistoric peat bogs, during successive intervals of time, by
lakes or shallow seas. Thus their vegetation was killed, and they were
overspread with layers of mud or sand, above which, during a subsequent
period of elevation, a new peat bog would form; and this process was
repeated several times. The conversion of the peat into coal appears
to have resulted from the pressure of the overlying strata, probably
aided by the internal heat of the earth. Much of its moisture was
squeezed and evaporated out; the proportions of its component gases
were reduced; and the result was a hard mineral, which has earned
the popular name of “black diamond” because consisting chiefly of
carbon--the same chemical element which, in a pure and crystalline
form, constitutes the true diamond. Chemically, coal consists of
carbon; the gases hydrogen, nitrogen and oxygen; sulphur; and ash (the
mineral matter that remains after combustion).

[Illustration: Courtesy of United States National Museum

Comparative coal supplies of the world. The nick in the smallest cube
shows how much hard coal has been used up. Soft coal cube has hardly
been scratched]

The record of these long-ago events is found when we sink a shaft
through typical coal-bearing strata. We pass through not one, but
several, layers of coal, which may vary in thickness from a fraction of
an inch to a hundred feet or more, and are separated by generally much
thicker layers of sandstone or shale (solidified clay). The layers of
coal are known as “coal-beds.” Unless a coal-bed is at least two feet
thick it is hardly worth working, and, ordinarily, the thickness of a
bed does not exceed eight or ten feet. The shale or sandstone above a
bed is very commonly found to contain the remains or the impressions
of the ancient plants from which the coal was formed. A study of these
remains and casts has made it possible to classify hundreds of species
of plants now extinct. Fragments of plants are also sometimes found in
the coal itself, and thin slices of coal frequently show a vegetable
structure under the microscope. Finally, to furnish conclusive proof
of the vegetable origin of coal, we find under the coal-bed a layer
known as the “underclay,” which is a fossil soil filled with the roots
and rootlets of the coal-producing plants. Different conditions of
formation, and also, probably, differences in the character of the
original vegetation, have resulted in the production of different kinds
of coal. The most important heat-producing constituent in coal is the
elementary substance called “carbon,” and the simplest classification
of solid fuels depends upon the percentages of fixed (non-volatile)
carbon they contain, the average percentages running as follows: Wood,
50%; peat, 55%; lignite, 73%; bituminous coal, 84%; anthracite coal,
93%. When fuel is burned the greater part of it unites chemically with
the oxygen of the air to form certain invisible gases--especially
carbon dioxide and water-vapor--and only the ash remains.

[Illustration: From “Geology, Physical and Historical,” by H. P.
Cleland. American Book Co., N. Y.

Section of coal-bearing strata in Pennsylvania, showing relative amount
of coal and barren rock in a rich field]

In the popular mind coal is classified as hard or soft, while hard coal
is further classified according to the size of the lumps. For both
scientific and industrial purposes more elaborate classifications are
necessary, and several have been used or proposed.

[Illustration: COAL FIELDS OF THE UNITED STATES]


_Kinds of Coal_

The United States Geological Survey classifies coals, first of all,
according to “rank,” depending upon both chemical and physical
characteristics. Anthracite, which contains the largest percentage of
carbon, ranks highest, and lignite, with the smallest percentage of
carbon, lowest. Coals of the same rank are said to be of high or low
“grade,” according to whether they contain a relatively small or large
percentage, respectively, of ash and sulphur. The ranks recognized
by the Survey are: Anthracite, semi-anthracite, semi-bituminous,
bituminous, sub-bituminous, and lignite.

[Illustration: Courtesy of U. S. Bureau of Mines

AN “ENTRY” IN A COAL MINE

Showing timbered roof]

[Illustration: Courtesy of U. S. Bureau of Mines

COATING WALLS OF A MINE WITH CEMENT

To prevent coal-dust explosions]

[Illustration: DRILLING IN COAL FOR BLASTING]

“Anthracite” is the hardest of coals. It was formed from bituminous
coal under the crushing pressure due to the upheaval of mountains or by
the intense heat of adjacent molten rocks. Most American anthracite is
mined in eastern Pennsylvania. The largest deposits in the world are
found in China. Anthracite burns slowly, with little smoke. It is well
adapted for domestic use on account of its cleanness, but is not an
economical fuel for steam-raising or general manufacturing.

[Illustration: Press Illustrating Service

MODERN ELECTRIC LOCOMOTIVE

Used for hauling coal from the mines]

“Semi-anthracite” also ranks as a hard coal, though it is less hard
than anthracite. Very little is mined in this country, and it is
generally sold as anthracite.

“Semi-bituminous” coal is a softer coal, which, when properly burned,
gives off but little smoke. The best semi-bituminous coal ranks highest
among the coals in heating value. It is the most valuable fuel for
manufacturing purposes; also for steamships, as it requires less bunker
space per unit of heat than any other coal.

“Bituminous” coal, or ordinary “soft coal,” burns readily, with a smoky
flame, and is the coal most commonly used for manufacturing purposes;
in fact, the bulk of the coal mined throughout the world belongs
to this rank. It includes a good many varieties, some of which are
extensively used in making coke, while others, such as “cannel” coal,
have been in great demand for use in gas-works. Nowadays, however, the
widespread introduction of “water-gas,”[2] which does not require any
particular kind of coal, has diminished the demand for “gas coals.”

    [2] Made by forcing steam over glowing coal or coke. See Monograph
    No. 4.

“Sub-bituminous” coal, or “black lignite,” is common in some of our
western coal fields. It is a clean and useful domestic fuel when used
near the mines, but is not very satisfactory for shipment, as it
shrinks and crumbles under the effects of “weathering” and is liable to
spontaneous combustion.

“Lignite” is the least valuable of coals, and is the form of coal which
is the least altered from the original peat. The Geological Survey
applies this name only to those coals which are distinctly brown and
either markedly woody or claylike in appearance. Lignite, as it comes
from the mine, contains from thirty to forty per cent. of moisture, and
it “slacks” or falls to pieces much more rapidly than sub-bituminous
coal when exposed to the air. It is hardly suitable for transportation.

For commercial purposes coal is also classified according to size.
The coal as it comes out of the mine, without any sorting into
sizes, is known as “run of mine,” and the semi-bituminous coals are
commonly shipped in this form. Most coals, however, are passed over
bars or gratings, which constitute screens of different degrees of
fineness; each screen permits all the lumps below a certain size to
fall through, and thus the coal is divided into the different standard
sizes. The sizes of anthracite, from the smallest to the largest,
are: rice, buckwheat, pea, chestnut (or nut), stove, egg, broken (or
grate), steamboat, and lump. Bituminous coal is divided into slack,
nut and lump (the largest size). A mixture of lump and nut is called
three-quarter coal.


_The Modern History of Coal_

[Illustration: Press Illustrating Service

MODERN MINING MACHINE

for undercutting coal. The “cutter bar” is shown in front, filled with
“cutting teeth” set in a chain that travels around.

See illustration opposite]

[Illustration: Press Illustrating Service

SHAKER SCREENS IN A TIPPLE HOUSE

The coal passing over screens is graded according to size]

[Illustration: “CUTTER BAR” AT WORK

The bar, with its cutting chain of teeth, makes a horizontal cut deep
into the bottom of the seam of coal. Blasting then does the rest]

The age of the steam-engine is also the age in which the use of coal
has become widespread, and the output of coal is a faithful index of
industrial progress. Although the Greek writer Theophrastus (about
300 B. C.) mentions the use of coal as a fuel, and its use was also
known to the ancient Britons and the Chinese, it was virtually unknown
throughout the Middle Ages. The first record of coal mining in England
is of the year 1180 A. D., and coal was first shipped to London in
the year 1240. It was long known as stone-coal, pit-coal, etc., to
distinguish it from charcoal; also as sea-coal, on account of being
carried to London by sea. Bituminous coal was first mined in America
in 1750, near Richmond, Virginia. Anthracite was discovered in Rhode
Island in 1760, and in Pennsylvania in 1766, but for many years its
value was not recognized. As late as the year 1812 Colonel George
Shoemaker, of Pottsville, was treated as an impostor and threatened
with arrest for attempting to sell a few wagon-loads of anthracite in
Philadelphia; methods of burning it were not understood, and it was
declared to be merely “black stone.” In the year 1820 only 365 tons
of anthracite were sold in this country, as compared with the present
annual output of about 90,000,000 tons.

Before the days of the railway coal was shipped mostly by water in
rough boats called “arks,” which floated down the rivers to the
seaboard towns. As it was impossible to return against the current,
the ark was sold with the coal at its destination. A great many arks
were wrecked in transit, and the whole process of transportation was
a costly one. Only with the introduction of steamboats, canals and
railways, did the coal industry assume serious proportions.

The production of coal in America has grown at an amazing rate. In the
year 1868 Great Britain produced 3.6 times as much coal as the United
States, and the output was also exceeded by that of Germany. In 1899,
the United States took the lead. At the present time, with an estimated
production for the year 1917 of 643,600,000 tons, the United States is
producing nearly half of all the coal mined in the world. Great Britain
ranks second, closely followed by Germany.


_How Coal is Mined_

A relatively small amount of coal is quarried near the surface of the
ground from open pits. The overlying soil is removed by steam-shovels,
and the coal is then blasted out and shoveled into cars.

Most coal is mined underground. Access to the coal-beds is obtained
either by sinking a vertical “shaft” or by driving a tunnel, according
to the location of the beds. A tunnel driven at a steep angle is called
a “slope.” A horizontal tunnel leading into a coal-seam is called a
“drift.” In this country few coal mines are more than 300 or 400 feet
below the surface, and the deepest is about 1,600 feet. Much deeper
mines are found in Europe, especially in Belgium.

[Illustration: Press Illustrating Service

ROTARY DUMP IN A TIPPLE

Showing a coal car half turned over in order to dump contents]

[Illustration: Courtesy of “Coal Age”

SPIRALIZING MACHINES

which, by rotating motion, separate the coal from slate]

[Illustration: Courtesy of U. S. Bureau of Mines

MODERN HEADFRAME, BINS AND TRESTLE

Of fireproof construction. Anthracite coal mine]

American mine shafts are generally rectangular and are divided into two
or more compartments. Where a shaft passes through water-bearing strata
it must be provided with a tight lining, or “tubbing,” to prevent the
mine from being flooded. All water that enters the mine collects in an
excavation, or “sump,” at the bottom of the shaft, and must be pumped
to the surface.

The method of working coal-seams most commonly practiced in this
country is known as the “room-and-pillar” system. One or more tunnels,
or “entries,” are first driven from the bottom of the shaft or the
mouth of the drift. These are the main thoroughfares of the mine, and
are usually provided with tracks, over which the mine cars are hauled
by mules or by some other method of traction--locomotives, endless
chains, etc. Secondary entries (“headings,” “butt entries,” etc.)
branch off from the main entries. Finally, the work of extracting the
coal consists of excavating open spaces, or “rooms,” adjoining the
entries.

[Illustration: Courtesy of “Coal Age”

MODEL COAL BREAKER

Note the neat and careful “upkeep” of the place]

The actual mining is done in the rooms, and different methods are in
use. Anthracite is generally “shot from the solid”; that is, blasted
out from the face of the coal without any preliminary cutting. This
method is objectionable, especially in bituminous mines (where it
is, however, much practiced), because the large charges of powder it
requires produce a great deal of coal-dust and weaken the roof and
pillars, often leading to falls of coal and fatal accidents. A better
plan consists of “undercutting” the coal before it is blasted out. A
long groove is made at the level of the floor, either with a pick or
with a coal-cutting machine. Holes are then drilled some distance above
the groove for the insertion of the blasting charges, and the coal is
blasted down. A single shot will sometimes dislodge a ton or two of
coal.

The next step is to shovel the coal from the floor into a mine car,
which is then pushed into the adjacent entry. The miner attaches a
numbered tag to the car, so that he will be duly credited for his work,
which is paid for by the ton. The loaded cars are eventually hoisted or
hauled out of the mine, to be weighed and discharged above ground.

The final step in working a coal-seam by the room-and-pillar method is
to mine out the thick walls or pillars of coal, which are originally
left between adjacent rooms to support the roof. As this work proceeds
the worked-out sections are filled with waste rock, or the roof is
allowed to fall. The object is to leave as little coal in the mine as
possible, but practically it is rare that more than 60 or 70 per cent.
is recovered.

One feature of a coal mine that must be carefully planned is the
system of ventilation. This is provided not merely for the comfort of
the miners, but to prevent, as far as possible, the accumulation of
poisonous and explosive gases. There are always at least two airways
leading into the mine (one or both of which may also be used for
hoisting or other purposes), known as the “upcast” and the “downcast,”
according to the direction in which the air passes through them. A
current of air is maintained either by keeping a fire burning at the
bottom of the upcast or by the use of powerful fans or blowers. A
system of tight trap-doors prevents the air from taking a short cut
between the downcast and the upcast, and thus leaving the greater part
of the mine unventilated.

[Illustration: Courtesy of “Coal Age”

MINING FROM THE OUTSIDE

Stripping the surface of a coal-bed with steam shovel, at Pittsburg,
Kans.]

[Illustration: Courtesy of U. S. Bureau of Mines

WATCHING THE CANARY

for indications of poisonous coal gas. Reserves testing the air of a
mine after an explosion]

[Illustration: Courtesy of U. S. Bureau of Mines

MEMBERS OF RESCUE TEAM

Showing apparatus worn on entering mines after explosions. This device
sustains a man for two hours]

The coal in the mine constantly gives off various gases, one of which,
the notorious “fire-damp” (methane or marsh-gas), is responsible for
many explosions. In recent years it has been discovered that coal-dust
itself, when mixed with the right proportion of air, is violently
explosive. Mine explosions may be minimized by requiring the use of
“safety-lamps” (oil, gasoline, or electric); by providing devices to
prevent sparking in electrical apparatus; and by using for blasting
operations only so-called “permissible” explosives, which give a
shorter and cooler flame than black powder. Coal-dust explosions can
be largely prevented by wetting the walls of the mine, or by the new
process of “rock-dusting,” which consists of applying dry incombustible
powdered rock to all surfaces. Unfortunately, none of these precautions
are employed as generally as they should be.

[Illustration: Press Illustrating Service

SAFETY DEVICE IN COAL BUNKER

In case of a “coal slide,” a man may be pulled out before he is buried
and stifled]


The elevator used for hoisting in the mine shaft is called a “cage.”
After the mine cars reach the surface they pass upon an elevated
structure called the “tipple.” This is generally the most conspicuous
feature of a mining property above ground, and provides facilities for
screening and otherwise “preparing” the coal as it passes down chutes
to the railway cars underneath. The more elaborate structure used for
anthracite is called a “breaker”; it includes machinery for crushing
the coal and arrangements for removing “slate” and other waste rock by
hand picking or otherwise.

Coal mining in this country gives employment to an army of 765,000 men.
The word “army” has a sinister appropriateness in this connection,
since out of every thousand men employed in the industry three are
killed and one hundred and eighty injured annually.


_The World’s Coal Resources_

In order of output, the leading coal-producing countries of the world
are: United States, Great Britain, Germany, Austria-Hungary, France,
Russia, Belgium, Japan, China, India, and Canada. The total production
during the latest year for which data are available was about
1,346,000,000 tons.

How long will the world’s coal supply last? This is a question to which
various answers have been given. Geologists are able to furnish a rough
estimate of the amount of coal now in the ground and near enough to
the surface to be mined; but with the growth of the world’s industries
the demand for coal is increasing by leaps and bounds, and nobody can
safely predict how much will be needed at any future time.

The world’s “coal reserves”--that is, the amount of coal remaining
unmined--are estimated at 8,154,322,500,000 tons. In the United States
it is estimated that we have used only four-tenths of one per cent. of
our available coal supply. At the _present_ rate of consumption the
coal in this country would last about 4,000 years; but if the present
rate of _increase_ in consumption should be maintained, it would last
only 100 years!

Fortunately for posterity there are sources of heat, light and power
which are not, like the fuels, exhaustible. Water-power, for example,
is a permanent asset, and there are other inexhaustible sources of
energy, such as solar heat and the internal heat of the earth, which
Man’s ingenuity will someday turn to good account.

[Illustration: Courtesy of “Coal Age”

CARS FOR CARRYING EXPLOSIVES INTO MINES]


_SUPPLEMENTARY READING_

  COAL CATECHISM                                      _By W. J. Nicholls_

  THE STORY OF AMERICAN COALS                         _By W. J. Nicholls_

  A YEAR IN A COAL MINE                               _By Joseph Husband_

  YEAR BOOK OF THE U. S. BUREAU OF MINES
  STORY OF A PIECE OF COAL                              _By E. A. Martin_

  THE COAL FIELDS OF THE UNITED STATES
  (U. S. Geological Survey, Professional Paper 100)   _By M. R. Campbell_

⁂ Information concerning these books may be had on application to the
Editor of The Mentor.




_THE OPEN LETTER_


Coal is “a burning question,” that has to be met and answered every
day. It supplies heat, light and power--and a thousand and one useful
by-products--and it is an ever-present, ever-fruitful subject of
public and private discussion. We average folk know something of the
varied uses of coal in the big affairs of the world, but we know it
more intimately and vitally in the forms in which it ministers to our
own personal welfare. Coal, in our everyday--and night--life, means
heat and light. It means home comfort--and if this “coal comfort” is
denied us, or even curtailed, we raise an immediate and mighty outcry.
And why not? The health of a community can be fatally affected by a
few heatless days. The experience of the past winter has shown us how
dependent we are on fuel, not only for luxury and comfort, but for life
itself.

       *       *       *       *       *

Why do we need so much heat? Many of the peoples of the earth get along
comfortably with much less heat than we consider necessary. Europeans
and South Americans call us a “steam-heated nation.” Why do we have
to surrender so completely and abjectly to the domination of Old King
Coal? It is true, as Owen Meredith said: “Civilized man cannot live
without cooks”; and light is all important in turning night hours to
advantage; but why must we be so warm? Humanity was not created in
a warm room, nor was the human race nurtured, in its infancy, by a
coal fire or a gas stove. Primitive man was his own heater. He had to
_discover_ fire, and then exploit its uses. He was originally supplied
by nature with a warm body, and he now finds artificial ways of making
it warmer. Has not civilization pampered us to a point that has
impaired our original heat-giving resources and substituted a forced
warmth that has enervated us? The doctors tell us that many diseases
come out of artificial heat--indoor diseases, they might be called--the
diseases that are treated, and sometimes cured today, by foregoing
artificial heat and going back to nature.

       *       *       *       *       *

Does this mean that I suggest reverting to primitive conditions and
giving up heat? No, indeed. I suffered enough last winter. I do
not advocate giving up heat--suddenly. But letting up gradually on
artificial heat, I do most earnestly advocate. Most of us live an
over-heated existence--to the depletion of our health. The steam pipe,
like a huge python, is closing its coils about us, and gradually
stifling our native vital resources.

       *       *       *       *       *

On the coldest days of winter a white-haired man, nearly seventy years
of age, may be seen walking New York streets, without a hat, clad only
in light “Palm Beach” trousers, and a silk negligée shirt, open at the
throat. “He is crazy,” you say. “Perhaps,” I answer, “but at any rate
he is healthy--and immune from cold.” Heatless days mean nothing to
him. On a raw, drizzling day in November last a slender man was playing
golf in a light woolen suit. A companion player, weighing over 200
pounds, full blooded and hearty in appearance, and bundled up in two
heavy sweaters, asked the lightly clad player if he was not afraid of
catching a fatal cold. “No,” he answered, “_you_ are the one that gives
me concern. If I had your clothing on I would be a sick man. _I am not
healthy enough_ to wear all those things.”

       *       *       *       *       *

Which means that we would be better off in health if we could accustom
ourselves to less heat; if we could live as the people of some other
nations do--comfortable and content with heat enough to take the chill
off the air, and not demanding that we shall be “kept going” by means
of artificial heat outside of our own natural heat-giving apparatus.
We make caloric cripples of ourselves by giving crutches to nature in
the form of roaring furnaces and hissing steam pipes. Fresh cold air is
better for us than hot air--in winter as well as in summer. Would it
not be worth while to form a national Fresh Air Fraternity, based on
the principle of foregoing artificial heat and developing the original
body caloric? We would then leave artificial heat largely to infants,
weaklings and invalids; we would abolish several diseases altogether,
improve the mortality rate, and be healthy, happy and vigorous.
Incidentally, too, we would have more coal for cooking and other really
necessary purposes.

[Illustration: W. D. Moffat

EDITOR]




IN THE HIGH SCHOOL


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It isn’t the “new” but the old things it tells, that are not generally
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J. B. SHEETZ, Principal, McClellandtown, Penn.


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