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Page 3
When vegetable matter is excluded from air and under great pressure, it
decomposes slowly, parting with carbonic acid gas; and is first changed
into lignite or brown coal, and then into bituminous coal, or the soft
coal that burns with smoke and flame. I have been in a coal-mine where
the carbonic acid gas, pouring from a crevice in the coal, put out a
lighted candle. The high temperature to which the coal has been
subjected when buried at great depths has also probably assisted in
producing this change; and where that temperature has been very high,
the coal by the influence of the heat having parted with its inflammable
gases, we have the hard or anthracite coal, which burns with little or
no flame and without smoke. It is indeed coal made into coke under
tremendous pressure, and this is the kind of coal which Americans use
exclusively in their dwelling-houses and monster hotels.
It was at first supposed that the plants of the carboniferous times were
bamboos, palms, and gigantic cactuses, such as are now found in tropical
regions, but a more careful examination of them shows that, with the
exception of the tree-fern now found in the tropics, they differ from
all existing trees. A large proportion of the plants of the
coal-measures were ferns, some authorities say one-half. From their
great abundance we may infer the great heat and moisture of the
atmosphere at the time when they grew, as similar ferns at the present
day are only found in the greatest abundance on small tropical islands
where the temperature is high. Coal often contains impressions of fern
leaves and palm-like ferns--no less than 934 kinds are drawn and
described by geologists. Many animals and insects are found in the coal,
such as large toad-like reptiles with beautiful teeth, small lizards,
water lizards, great fish with tremendous jaws, many insects of the
grasshopper tribe, but none of these are of the same species as those
found now living on this globe.
Wood, peat, brown coal, jet, and true coal, are chemically alike,
differing only in their amount of oxygen, due to the difference of
compression to which they were subjected. The sun gave his heat and
light to the forests now turned into coal, and when we burn it ages
afterwards, we revive some of the heat and light so long untouched.
Stephenson once remarked to Sir Robert Peel, as they stood watching a
passing train: "There goes _the sunshine of former ages_!"
COST OF WORKING.
Having thus stated shortly the origin and extent of the coal of this
country, more particularly that of the northern coal-fields of
Northumberland and Durham, I think it may be interesting to say
something of the cost at which this valuable article is obtained, as I
am sure few are at all aware of the vast sums of money that have to be
expended before we can sit down by our comfortable firesides, with a
cold winter night outside, and read our book, or have our family
gathered round us; and few know the danger and hardship of the bold
worker who risks his life to procure the coal. The first step is to find
out if there is coal. This done, the next is to get at it, or, as it is
termed, to _win_ the coal. The process is to sink a shaft, and this is
alike dangerous, uncertain, and very costly. The first attempt to sink a
pit at Haswell in Durham was abandoned after an outlay of �60,000. The
sinkers had to pass through sand, under the magnesian limestone, where
vast quantities of water lay stored, and though engines were erected
that pumped out 26,700 tons of water per day, yet the flood remained the
conqueror. This amount seems incredible, but such is the fact. At
another colliery near Gateshead (Goose Colliery), 1000 gallons a minute,
or 6000 tons of water per day, were pumped out, and only 300 tons of
coal were brought up in the same time, and thus the water raised
exceeded the coal twenty times. The most astonishing undertaking in
mining was the Dalton le Dale Pit, nine miles from Durham. On the 1st
June 1840 they pumped out 3285 gallons a minute. Engines were erected
which raised 93,000 gallons a minute from a depth of 90 fathoms or 540
feet, and this was done night and day. The amount expended to reach the
coal in this pit was �300,000. Mr. Hall estimates the capital invested
in the coal trade of the counties of Durham and Northumberland,
including private railways, waggons, and docks for loading ships, at
�13,000,000 sterling.
The great difficulty in working coal, should these upper seams fail, is
not only the increase of cost in sinking further down, but the increased
heat to be worked in. At 2000 feet the mine will increase in heat 28�,
at 4000, 57�; to this must be added the constant temperature of 50� 5',
so that at 2000 feet it would be 78� 5', and at 4000, 107� 5' Fahr. By
actual trial on July 17, 1857, in Duckingfield Pit, the temperature at
2249 feet was 75� 5'. From this it may be conceived in what great heat
the men have to work, and the work is very hard. One may fancy from this
what can be endured, but it would be next to impossible to work in a
greater temperature. I can speak upon this from actual experience, as
when down the Lady Londonderry Pit the temperature was 85�, and here the
men worked naked. Another great source of expense and anxiety lies in
keeping up the roof, as, from the excessive pressure, the roof and floor
are always inclined to come together, and props must therefore be used,
and these in some pits cost as much as �1500 a year. To digress for a
moment, an amusing story is told of Grimaldi, the celebrated clown, when
paying a visit to a coal-pit. Having gone some way through the mine, a
sudden noise, arising from the falling of coal from the roof, caused him
to ask the reason of the noise. "Hallo!" exclaimed Grimaldi, greatly
terrified, "what's that?" "Hech!" said his guide, "it's only a wee bit
of coal fallen down--we have that three or four times a day." "Then I'll
thank you to ring for my basket, for I'll stop no longer among the wee
bits of falling coal." This "wee bit" was about three tons' weight. A
large proportion of the sad accidents in coal-mines is caused by these
falls of the roof, which give no warning, but suddenly come down and
crush to death those who happen to be near.
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