Coal is one of the most valuable of all mineral treasures, and one that
is of the highest service in making the others available to the use and
comfort of man. And hence it has been searched after with unremitting
diligence, and worked with all the lights of science and the resources
of art. It is found in beds or strata, in that group of the secondary
rocks which includes the red sandstone and mountain limestone
formations, commonly called the _carboniferous group_, or the _coal
measures_. From the peculiarities of their position, they are often
spoken of as _coal-basins_, and _coal-fields_.
There are two or three points of some theoretical interest and
importance as to the origin of coal, on which geological authorities are
nearly unanimous. One is, that our present coal is exclusively of
vegetable origin, formed apparently from the destruction of vast forests
and immense quantities of leaves and shrubs; another, that it was formed
when the climate of the regions where it is found was not merely
tropical, but ultra-tropical, instead of being as now, temperate; and a
third, that its deposits, though originally regular, have evidently been
since elevated, and often singularly dislocated and contorted by forces
acting from below, and probably of a volcanic nature. Each of these
points will more or less appear in the progress of the following
remarks.
That the coal formations are of vegetable origin, is perfectly evident
from even a slight examination, especially with the microscope. Let a
piece of coal be cut in very thin slices, or plates, and its appearance
will be like that seen in the following cut. The vegetable fossils thus
shown are, indeed, very different from any existing species, unless it
be a few which are the productions only of torrid climates. And while
the cut gives the appearance of but a _single leaf_ in each specimen,
the masses of coal are generally more like one thick imbedded mass of
leaves, not so much _crushed together_, as _overlaying_ and _mixed with_
each other. According to Dr. Linley, the coal vegetation consisted of
ferns, in great abundance; of large coniferous trees, of a species
resembling =lycopodiacæ=, but of most gigantic dimensions; of a numerous
tribe apparently analogous to =cactæ=, but probably not identical with
them; of palm, and other _monocotyledones_; and finally, of numerous
vines, plants, &c., the exact nature of which is uncertain. Where
_leaves_ most abound, the coal is said to be of the best quality; though
as any one kind of coal hardens, the impressions of such leaves become
gradually less distinct, until finally they can hardly be traced, even
with a powerful magnifier. A hundred and twenty varieties of these
vegetable impressions have been found in the vicinity of Pottsville, in
the course of a few months, each as distinctly marked as the most
delicate tracings of an artist’s pencil; and in almost any coal
formation, there are so many hundreds of different plants, trees, and
flowers, that a single representative of each kind would form a vast
museum. Specimens which exhibit impressions of the bark, limbs, or
trunks of trees, are, of course, correspondingly large and heavy, and
could not easily be sketched in a small engraving, while the variety of
leaves and flowers is so great, that it would be tedious to mention and
describe them.
[Illustration: THIN PLATES OF COAL.]
With these few remarks, we proceed to notice first, some of the coal
mines of Great Britain, and then some of our own country. Perhaps there
is no country where coal mines are so rich, so frequent, and so
successfully worked thus far, as those of Great Britain; and it is to
this cause that the opulence of that country has often been chiefly
ascribed. It is, in truth, the coal of her mines, that is the very life
of her manufactures, and consequently of her commerce, every
manufacturing town being established in the midst of a coal country. Of
this striking instances are afforded by Bristol, Birmingham,
Wolverhampton, Sheffield, Newcastle, and Glasgow.
The coals of Whitehaven and Wigan are esteemed the purest; and the
cannel and peacock coals of Lancashire are so beautiful, that they are
suspected by some to have constituted the _gagates_, or jet, which the
ancients ascribed to Great Britain. In Somersetshire, the Mendip coal
mines are distinguished by their productiveness: they occur there, as
indeed in every other part, in the _low_ country, and are not to be
found in the hills. The beds of coal are not horizontal, but sloping,
dipping to the south-east at the rate of about twenty-two inches per
fathom. Hence they would speedily sink so deep that it would not be
possible to work them, were it not that they are intersected at
intervals by perpendicular dikes or veins, of a different kind of
mineral, on the other side of which these beds are found considerably
raised up. They are seven in number, lying at regular distances beneath
each other, and separated by beds of a different kind of substance, the
deepest being placed more than two hundred feet beneath the surface of
the earth.
The town of Newcastle, in Northumberland, has been celebrated during
several centuries for its very extensive trade in coal. It was first
made a borough by William the Conqueror, and the earliest charter for
digging coals, granted to the inhabitants, was in the reign of Henry
III., in 1239; but in 1306, the use of coal for fuel was prohibited in
London, by royal proclamation, chiefly because it injured the sale of
wood, with which the environs of the capital were then overspread. This
interdict did not, however, continue long in force; and coals may be
considered as having been dug for exportation at Newcastle for more than
four centuries. It has been estimated that there are twenty-four
considerable collieries lying at different distances from the river,
from five to eighteen miles; and that they produced, for an average of
six years, up to the close of 1776, an annual consumption of three
hundred and eighty thousand chaldrons, Newcastle measure, (equal to
seven hundred and seventeen thousand, six hundred and fifteen chaldrons,
London measure,) of which about thirty thousand chaldrons were exported
to foreign parts. The boats employed in the colliery are called _keels_,
and are described as strong, clumsy, and oval, each carrying about
twenty tuns; and of these four hundred and fifty are kept constantly
employed. In the year 1776 an estimate was made of the shipping employed
in the Newcastle coal trade; and from this estimate it appears, that
three thousand, five hundred and eighty-five ships, were during that
year engaged in the coasting trade, and three hundred and sixty-three in
the trade to foreign ports, their joint tunnage amounting to seven
hundred and thirty-eight thousand, two hundred and fourteen tuns.
As already said, it is a common opinion among geologists, that coal is
of vegetable origin, and that it has been brought to its present state
by the means of some chemical process, not at this time understood. This
opinion is abundantly supported by the existence of vast depositions of
matter, halfway, as it were, between perfect wood and perfect coal;
which, while it obviously betrays its vegetable nature, has in several
respects so near an approximation to coal, as to have been generally
distinguished by the name of coal. One of the most remarkable of these
depositions exists in Devonshire, about thirteen miles south-west of
Exeter, and is well known under the name of Bovey coal. Its vegetable
nature has been ascertained by Mr. Hatchet, in a set of experiments in
which he found both extractive matter and resin, substances which belong
to the vegetable kingdom.
The beds of this coal are seventy feet in thickness, and are
interspersed with beds of clay. On the north side they lie within a foot
of the surface, and dip south at the rate of about twenty inches per
fathom. The deepest beds are the blackest and heaviest, and have the
closest resemblance to coal, while the upper ones strongly resemble
wood, and are considered as such by those who dig them. They are brown,
and become extremely friable when dry, burning with a flame similar to
that of wood, and assuming the appearance of wood which has been
rendered soft by some unknown cause, and, while in that state, has been
crushed flat by the weight of the incumbent earth. This is the case, not
only with the Bovey coal, but also with all the beds of wood-coal which
have been hitherto examined in different parts of Europe.[5]
Footnote 5:
We are informed by Liebig and other eminent chemists, that when wood
and other vegetable matter are buried in the earth, exposed to
moisture, and partially or entirely excluded from the air, they
decompose slowly, and evolve carbonic acid gas; thus parting with a
portion of their original oxygen. By this means they are gradually
converted into lignite, or wood-coal, which contains a larger
proportion of hydrogen than wood does. A continuance of decomposition
changes this lignite into common or bituminous coal, chiefly by the
discharge of carbureted hydrogen, or the gas by which we illuminate
our streets and houses. According to Birchoff, the inflammable gases
which are always escaping from mineral coal, and are so often the
cause of fatal accidents in mines, always contain carbonic acid,
carbureted hydrogen, nitrogen, and olefiant gas. The disengagement of
all these gradually transforms ordinary or bituminous coal into
anthracite, to which the various names of splint-coal, glance-coal,
culm, and many others, have been given.
The coal mines of Whitehaven may be considered as among the most
extraordinary in the known world. They are excavations which have, in
their structure, a considerable resemblance to the gypsum quarries of
Paris, and are of such magnitude and extent, that in one of them alone,
a sum exceeding half a million sterling, was, in the course of a
century, expended by the proprietors. Their principal entrance is by an
opening at the bottom of a hill, through a long passage hewn in the
rock, leading to the lowest vein of coal. The greater part of this
descent is through spacious galleries, which continually intersect other
galleries, all the coal being cut away, with the exception of large
pillars, which, where the mine runs to a considerable depth, are nine
feet in hight, and about thirty-six feet square at the base. Such is the
strength there required to support the ponderous roof.
The mines are sunk to the depth of one hundred and thirty fathoms, and
are extended under the sea to places where there is, above them,
sufficient depth of water for ships of large burden. These are the
deepest coal mines which have hitherto been wrought; and perhaps the
miners have not, in any other part of the globe, penetrated to so great
a depth beneath the surface of the sea, the very deep mines in Hungary,
Peru and elsewhere, being situated in mountainous countries, where the
surface of the earth is elevated to a great hight above the level of the
ocean.
In these mines there are three strata of coal, which lie at a
considerable distance one above the other, and are made to communicate
by pits; but the vein is not always continued in the same regularly
inclined plane, the miners frequently meeting with hard rock, by which
their further progress is interrupted. At such places there seem to have
been breaks in the earth, from the surface downward, one portion
appearing to have sunk down, while the adjoining part has preserved its
ancient situation. In some of these places the earth has sunk ten,
twenty fathoms, and even more; while in others the depression has been
less than one fathom. These breaks the miners call _dikes_, and when
they reach one of them, their first care is to discover whether the
strata in the adjoining part are higher or lower than in the part where
they have been working; or, according to their own phrase, whether the
coal be _cast down_ or _cast up_. In the former case they sink a pit;
but if it be cast up to any considerable hight, they are frequently
obliged, with great labor and expense, to carry forward a level, or long
gallery, through the rock, until they again reach the stratum of coal.
Coal, the chief mineral of Scotland, has been there worked for a
succession of ages. Pope Pius II., in his description of Europe, written
about 1450, mentions that he beheld with wonder black stones given as
alms to the poor of Scotland. This mineral may, however, be traced to
the twelfth century; and a very early account of the Scottish coal
mines, explains with great precision, the manner of working the coal,
not neglecting to mention the subterraneous walls of _whin_ which
intersect the strata, particularly a remarkable one, visible from the
river Tyne, where it forms a cataract, and passes by Prestonpans, to the
shore of Fife. The Lothians and Fifeshire, particularly abound with this
useful mineral, which also extends into Ayrshire; and near Irwin is
found a curious variety, named ribbon-coal. A singular coal, in veins of
mineral, has been found at Castle Leod, in the east of Ross-shire; and
it is conjectured that the largest untouched field of coal in Europe,
exists in a barren tract of country in Lanarkshire.
The process of mining coal is a combination of boring and digging.
Shafts are sunk, levels are driven, and drains are carried off, by the
help of picks or pickaxes, wedges and hammers, the rocks being also
sometimes loosened by blasting with gunpowder. In searching for coal, a
shaft is sunk through the uppermost soft stratum, and the rock is then
bored, by striking it continually with an iron borer terminating in an
edge of steel, which is in the mean time turned partly round; and, at
proper intervals, a scoop is let down to draw up the loose fragments. In
this manner a perforation is sometimes made for more than an hundred
fathoms, the borer being lengthened by pieces screwed on; it is then
partly supported by a counterpoise, and worked by machinery. Should it
happen to break, the piece is raised by a rod furnished with a hollow
cone, as an extinguisher, which is driven down on it. The borer is
sometimes furnished with knives, which are made to act on any part at
pleasure, and to scrape off a portion of the surrounding substance,
which is collected in a proper receptacle.
Those who have the direction of deep and extensive coal mines, are
obliged, with great art and care, to keep them ventilated with perpetual
currents of fresh air, which afford the miners a constant supply of that
vital fluid, and expel from the mines damps and other noxious
exhalations, together with such other burnt and foul air, as has become
deleterious and unfit for respiration. In the deserted mines, which are
not thus ventilated with currents of fresh air, large quantities of
these damps are frequently collected; and in such works they often
remain for a long time without doing any mischief. But when, by some
accident, they are set on fire, they then produce dreadful explosions,
and, bursting out of the pits with great impetuosity, like the fiery
eruptions from burning mountains, force along with them ponderous bodies
to a great hight in the air.
Various instances have occurred in which the coal has been set on fire
by the fulminating damp, and has continued burning for several months,
until large streams of water were conducted into the mine, so as to
inundate the parts where the conflagration existed. By such fires
several collieries have been entirely destroyed, in the vicinity of
Newcastle, and in other parts of England, as well as in Fifeshire, in
Scotland. In some of these places the fire has continued to burn for
ages. To prevent, therefore, as much as possible, the collieries from
being filled with these pernicious damps, it has been found necessary
carefully to search for the crevices in the coal whence they issue, and,
at those places, to confine them within a narrow space, conducting them
through large pipes into the open air, where, being set on fire, they
consume in perpetual flame as they continually arise out of the earth.
Mr. Spelling, an engineer of the Whitehaven coal mines, having observed
that the fulminating damp could only be kindled by flame, and that it
was not liable to be set on fire by red-hot iron, nor by the sparks
produced by the collision of flint and steel, invented a machine called
a steel-mill, in which a wheel of that metal is turned round with a very
rapid motion, and, by the application of flints, great plenty of sparks
are emitted, which afford the miners such a light as enables them to
carry on their work in close places, where the flame of a candle, or a
lamp, would, as has already happened in various instances, occasion
violent explosions. In that dreadful catastrophe, the explosion of the
Felling colliery, the particulars of which will be hereafter detailed,
it will be seen that mills of this description were employed, in
searching for the remains of the victims of the sad disaster; but this
event happened before the invention of Sir Humphrey Davy’s safety-lamp,
a discovery which, while it affords a more certain light, holds out
every security to the miner against accidents which, without such a
resource, might still be superadded to those already recorded, as
arising from the flame of a candle or lamp.
A greater number of mines have, however, been ruined by inundations than
by fires; and here that noble invention, the fire-engine, displays its
beneficial effects. It appears from nice calculations, that it would
require about five hundred and fifty men, or a power equal to that of
one hundred and ten horses, to work the pumps of one of the largest
fire-engines, having a cylinder seventy inches in diameter, now in use,
and thrice that number of men to keep an engine of that size constantly
at work. It also appears that as much water may be raised by such an
engine, as can be drawn, within the same space of time, by twenty-five
hundred and twenty men with rollers and buckets, after the manner long
practiced in many mines; or as much as can be borne on the shoulders of
twice that number of men, as is said to be done in several of the mines
of Peru. So great is the power of the elastic steam of the boiling water
in those engines, and of the outward atmosphere, which, by their
alternate actions give force and motion to the beam, and through it to
the pump rods which elevate the water through tubes, and discharge it
from the mine!
Years since there were four fire-engines belonging to the Whitehaven
colliery, which when all at work, discharged from it about twelve
hundred and twenty-eight gallons of water every minute, at thirteen
strokes; and at the same rate, one million, seven hundred and
sixty-eight thousand, three hundred and twenty gallons, upward of seven
thousand tuns, every twenty-four hours. By these engines nearly twice
the above-mentioned quantity of water might be discharged from mines not
more than sixty or seventy fathoms deep, which depth is rarely exceeded
in the Newcastle collieries, or in any other English collieries, with
the exception of the above.
Coal pits have sometimes taken fire by accident, and have continued to
burn for a considerable length of time. About the year 1648, a coal mine
at Benwell, a village near Newcastle-upon-Tyne, was accidentally kindled
by a candle: at first the fire was so feeble, that a reward of half a
crown, which was asked by a person who offered to extinguish it, was
refused. It gradually increased, however, and had continued burning for
thirty years, when the account was drawn up and published in the
Philosophical Transactions: it was not finally extinguished until all
the fuel was consumed. Examples of a similar kind have happened in
Scotland and in Germany.
But of all the recorded accidents relative to coal mines, that of
Felling colliery, near Sunderland, a concise narrative of which here
follows, was the most disastrous.
Felling is a manor about a mile and a half east of Gateshead. It
contains several strata of coal, the uppermost of which were extensively
wrought in the beginning of the last century. The stratum called the
high-main, was begun in 1779, and continued to be wrought till the
nineteenth of January, 1811, when it was entirely excavated. The present
colliery was in the seam called the low-main. It commenced in October,
1810, and was at full work in May, 1812. This mine was considered by the
workmen as a model of perfection in the purity of its air, and orderly
arrangements; its inclined plane was saving the daily expense of at
least thirteen horses; the concern wore the features of the greatest
possible prosperity, and no accident, except a trifling explosion of
fire-damp, slightly burning two or three workmen, had occurred. Two
_shifts_, or sets of men, were constantly employed, except on Sundays.
Twenty-five acres of coal had been excavated. The first shift entered
the mine at four o’clock, A. M., and were relieved at their
working-posts by the next at eleven o’clock in the morning. The
establishment employed under ground, consisted of about one hundred and
twenty-eight persons, who, from the eleventh to the twenty-fifth of May,
1812, wrought six hundred and twenty-four scores of coal, equal to
thirteen hundred Newcastle, or twenty-four hundred and fifty-five London
chaldrons.
About half past eleven o’clock, on the morning of the twenty-fifth of
May, 1812, the neighboring villages were alarmed by a tremendous
explosion in this colliery. The subterraneous fire broke forth with two
heavy discharges from the low-main, which were almost instantaneously
followed by one from the high-main. A slight trembling, as from an
earthquake, was felt for about half a mile around the workings; and the
noise of the explosion, though dull, was heard to three or four miles’
distance, and much resembled an unsteady fire of infantry. Immense
quantities of dust and small coal accompanied these blasts, and rose
high into the air, in the form of an inverted cone. The heaviest part of
the ejected matter, such as corves, pieces of wood, and small coal, fell
near the pits; but the dust, borne away by a strong west wind, fell in a
continued shower from the pit to the distance of a mile and a half. As
soon as the explosion was heard, the wives and children of the workmen
ran to the pit; the scene was distressing beyond the power of
description.
Of one hundred and twenty-eight persons in the mine at the time of the
explosion, only thirty-two were brought to daylight: twenty-nine
survived the fatal combustion; the rest were destroyed. Nor from the
time of the explosion till the eighth of July, could any person descend.
But after many unsuccessful attempts to explore the burning mine, it was
reclosed, to prevent the atmospheric air from entering it: this being
done, no attempt was afterward made to explore it, till the morning of
the last-mentioned day; from which time to the nineteenth of September,
the heart-rending scene of mothers and widows examining the putrid
bodies of their sons and husbands, for marks by which to identify them,
was almost daily renewed; but very few of them were known by any
personal mark; they were too much mangled and scorched to retain any of
their features. Their clothes, tobacco-boxes, shoes, &c., were,
therefore, the only indexes by which they could be recognized.
At the crane twenty-one bodies lay in ghastly confusion: some like
mummies, scorched as dry as if they were baked. One wanted its head,
another an arm. The scene was truly frightful. The power of fire was
visible upon them all; but its effects were extremely variable: while
some were almost torn to pieces, there were others who appeared as if
they had sunk down overpowered with sleep. The ventilation concluded on
Saturday the nineteenth of September, when the ninety-first body was dug
from under a heap of stones. At six o’clock in the morning the pit was
visited by candle-light, which had not been used in it for the space of
one hundred and seventeen days; and at eleven o’clock in the morning the
tube furnace was lighted. From this time the colliery has been regularly
at work; but the ninety-second body has never yet been found. All these
persons, except four, who were buried in single graves, were interred in
Heworth chapel-yard, in a trench, side by side, two coffins deep, with a
partition of brick and lime between every four coffins.
Having thus glanced at some of the coal mines of Great Britain, we now
pass to some of those of the United States. In these coal is found in
_four_ different forms: _first_, the _genuine_ anthracite, or _glance_
coal, as near Worcester, Mass., and Newport, R. I.; _second_, coal
destitute of bitumen, commonly called anthracite, but which is more
properly anasphaltic, which is found at Pottsville, Mauch Chunk,
Lackawanna, Wilkesbarre, &c.; _third_, bituminous coal, usually found in
the slate rock, as at Tioga, Lycoming, etc.; and _fourth_, the lignite
coal, found along the south shore of the bay of South Amboy, New Jersey.
From the state of Alabama to Pictou, Nova Scotia, the coal beds can be
followed in a north-east direction, for fifteen hundred miles; and from
Richmond, in Virginia, to Rock River, in Illinois, they are continually
crossed at right angles, for about eight hundred miles. At Richmond, the
coal is bituminous; on the Alleghany belt, it is anthracite. Geologists
think that the anthracite was lifted out of its horizontal position when
the great Alleghany belt was upheaved, and that its non-bituminous
quality is owing to the influence of the intense heat that accompanied
its upheaval.
Taylor, in his book on coal, estimates the area of bituminous coal in
the United States, east of the Mississippi river, at one hundred and
twenty-four thousand, seven hundred and thirty-five square miles, and
west of the Mississippi, at eight thousand, three hundred and
ninety-seven square miles; British North America, eighteen thousand
square miles bituminous. More than one-third of the area of
Pennsylvania, is more or less marked by coal formations; one-third of
Kentucky, Ohio and Virginia, one-fifth of Indiana, and three-fourths of
Illinois, are occupied by carboniferous strata. Western Pennsylvania
abounds in bituminous coal, and it is found also in several counties of
New York. By the census of 1839-40, we find that the quantity of
bituminous coal produced that year in the United States, was
twenty-seven million, six hundred and three thousand, one hundred and
ninety-one bushels, employing about four thousand men, and a capital of
some two million dollars; and that about four million dollars of capital
were invested in raising anthracite coal, of which some nine hundred
thousand tuns (of about twenty-eight bushels each) were produced by the
labors of about three thousand men. Most of this was from Pennsylvania.
In 1819, the anthracite coal trade had no existence; in 1820, this kind
of coal was first used as fuel, and just three hundred and sixty-five
tuns were sent to market; in 1845, the amount was two million tuns; in
1850, about three million, five hundred thousand tuns, and the present
year (1854) the amount will probably be between six and seven million
tuns. The demand and supply so steadily and rapidly increase that it is
impossible to estimate the vast extent the business of coal mining is
yet to attain.
Glancing for a moment at other countries, we find that Belgium, in 1845,
had two hundred and twelve mines, employing thirty-eight thousand miners
and five hundred steam-engines, and producing five million tuns; France,
four hundred and forty-nine mines, employing thirty thousand miners, and
producing five million tuns; Prussia, in 1840, seven hundred and
fifty-two mines, employing twenty-four thousand miners, and raising
three million, five hundred thousand tuns; and that Great Britain, in
1846, produced thirty-five million tuns, valued at forty-five million
dollars at the mines. Austria and Spain, also, have excellent mines,
though less productive. And as a late and interesting discovery, it may
be added, that the recent Arctic expedition sent out from England, found
coal in those northern regions, on the island of Disco, outcropping near
the shore. They also, in another locality not far off, discovered some
curious specimens of petrified trees, and near them extensive quarries
of anthracite coal, of good quality. There appeared to be no limit to
the quantity that might be thrown into a boat with ease, and in the
space of three hours they conveyed not less than twelve tuns to the
steamer, three-quarters of a mile distant. It proved, on trial, to be of
good quality, the combustion was perfect, and the coal as economical as
the Welsh.
We will conclude the subject of coal mines, with the statement of a
recent tourist, as to some of the wonders of the Cornish mines in
England, as he saw them in 1854. He says: “Some of the mines are truly
grand undertakings. The ‘consolidated mines,’ the largest of the Cornish
group, employ upward of three thousand persons. One of the engines pumps
water from a direct depth of sixteen hundred feet, the weight of the
pumping apparatus alone being upward of five hundred tuns; the
pumping-rod is one thousand, seven hundred and forty feet long, and it
raises about two million gallons of water in a week, from a depth equal
to five times the hight of St. Paul’s. These are, indeed, wonders to
marvel at! The consolidated and united mines, both belonging to one
company, are stated to have used the following vast quantities of
materials in a year: coals, fifteen thousand, two hundred and seventy
tuns; candles, one hundred and thirty-two thousand, one hundred and
forty-four pounds; gunpowder, eighty-two thousand pounds; leather, for
straps, &c., thirteen thousand, four hundred and ninety-three pounds;
pick and shovel handles, sixteen thousand, six hundred and ninety-eight
dozens. Sir Charles Lemon has estimated, that in the whole of the
Cornish mines, thirteen thousand pounds’ worth of gunpowder is used
annually; that the timber employed in the underground works, equals the
growth of one hundred and forty square miles of Norwegian forest; and
that thirty-seven million tuns of water are raised annually from the
mines.”