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canals, the quality of the coal, and its price at the pit's mouth; this last must be in a great degree regulated by the expense of bringing it to the surface, which is very variable, according to situations.

There are in England and Wales twelve great coal-fields, of which those marked I. II. IV. VI. XII. are the most important. These are,

1. The Northumberland and Durham Fields, the almost exclusive feeders of London, and supplying also the whole of the eastern and southern coasts from Berwick to Plymouth, and as far inland as the county of Bedford. Formerly the inland markets extended further; but the extension of canals has brought other and cheaper coals into competition. There is also a very large foreign export, and a considerable quantity is sent to Scotland.

II. The Yorkshire, Nottinghamshire, and Derbyshire Fields. III. The Whitehaven Fields.

IV. The South Lancashire Fields.

This, with the Yorkshire and Nottinghamshire Fields, are the foundation of our great national superiority in the woollen and cotton manufactures, the principal seats of which are upon them.

V. The North Staffordshire, or Pottery Fields. VI. The South Staffordshire, or Dudley and Warwickshire Fields,-not of great superficial extent, but immensely productive, and containing the thickest seam of coal in the island. It is also one great seat of our iron manufactures.

VII. The Shropshire Fields, including Colebrook Dale, and the Plain of Shrewsbury.

VIII. Forest of Dean Field.

IX. South Gloucestershire, or Bristol Fields.

X. Somersetshire Field.

XI. North Wales, or Flintshire Fields.

XII. The South Wales Fields, comparatively little worked as yet, but the most extensive of all, and upon which our posterity must depend, when the other fields are exhausted.

Thus it will be seen that all the coal-fields, and all the great seats of our manufactures, lie to the north and west of the line Z Z, which is the boundary of the middle and superior strata of the secondary series; for, with the exception of some detached points in Somersetshire and Glamorganshire on the Bristol Channel, neither the lias limestone, nor any of the formations superior to it (I. in the Diagram, p. 235) are found westward of that line. The new red sandstone K, which is immediately under the lias, and covers so vast a surface in the midland and northern counties, lies to the north and west of the line; many of the coal-fields are surrounded by it, and it is possible that others may be discovered within its domain, either where it is partially denuded, or where it is so thin that it may be sunk through without great expense. All searches for coal in the red sandstone itself would, according to every probability, end in disappointment.

The Newcastle coal-field is by far the most important of all those at present worked in England. The area covered by this coal-field will be seen by the map at the top of the next column.

The length of the coal-field, from the Tees to the Coquet, is almost fifty-five miles; its greatest breadth, between the mouth of the Tyne and the Western Pits, about twenty-two miles. It is bounded on the east, from a short distance south of Shields very nearly to its southern termination, by strata of magnesian limestone under which the coal-measures have been found to be prolonged in many places: along the northern half of its eastern limit, the coal-measures are exposed in the cliffs on the sea-shore. The whole of the western side is bounded by the Millstone Grit, upon which the coal-measures repose. (See Diagram, p. 235, L, M, N.)

The entire area contained within those limits is occupied by beds of sandstone and shale, of great variety of composition and thickness, interstratified with seams of coal, also of different

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degrees of thickness. The valuable seams of coal are in general very deep beneath the surface of the ground, and are got at by a circular opening like a well, called a shaft, which is sunk perpendicularly through the strata. The following enumeration of the different strata thus passed through in order to get at workable seams of coal in Bigge's Main Colliery, to the depth of 1158 feet, will show the numerous alternations of which the coal-measures consist in the Newcastle coal-field. The section is one of several given by Mr. N. J. Winch, a practical mining engineer, in his Observations on the Geology of Northumberland and Durham,' published in the 4th volume of the Transactions of the Geological Society.'

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They then came upon the first seam of coal, but From this seam to the thick bed called the High which had only a thickness of ...... Main Coal of the Tyne, they sunk through 29 different beds of sandstone and shale, varying in thickness from 40 inches to 31 feet, interstratified with 8 seams of coal from 5 to 18 inches thick, amounting together to ..... ..... 418

The High Main Coal of the Tyne had here a thick

ness of

From this seam they sunk farther through 52 beds of sandstone and shale, varying from 5 inches to 34 feet in thickness, interstratified with 19 different seams of coal from 2 to 37 inches thick, and amounting together to

7. They now came upon the seam of coal called the Low Main Coal of the Tyne, which had in this pit a thickness of...

8. And they sank beneath this through 10 different beds of stone, from 12 inches to 12 feet thick, and two seams of coal of 4 and 12 inches, making together...

and giving a total depth of.

2

6 8

503 2

2 9

S2

...1158

having passed through 125 different strata, including 32 seams of coal, 19 of which have been worked.

The coal-measures lie in an inclined position, and at different angles of inclination in different parts. The conse quence of this is, that the same seams are found at much greater depths from the surface in one colliery than in another. Nor will two distant parts of the field give the same succession of strata in a vertical section, either as regards the beds of stone, or the seams of coal, in point of quality and thickness: the same seam of coal swells out in one place, and in another thins off so much as not to be worth working, and the same thing occurs with the sandstone and shale; a bed of stone or seam of coal, which in one pit is scarcely perceptible, will increase in another pit to several feet. Neither are these coal strata continuous over the whole area. In many parts of the district, a vertical section of the ground would at one time have presented an appearance similar to the following:

h

Fig. 5.

but a section now shows that the surface has been deeply indented, and great portions of the superior strata have been carried away, so that it exhibits the following appearance. Fig. 6.

There are also several parts of the district where, although the other beds of the coal formation exist, the seams of coal are either altogether wanting, or are so mixed with bands or layers of stone, or are so thin, that they would not pay the expense of working them. It also frequently happens that, by the inclined position of the strata, the superior beds containing the best coal terminate at the surface, or crop out, as the miners call it. Thus, in Figure 5, the seam of coal a, which would be found by sinking a pit in any part of the country between e and f, crops out at f, and there terminates: in like manner the seam b crops out at g, and thus in the country between g and h, instead of having the three seams of coal, a, b, c, they have only the last of these. If they go deep in sinking their shaft they may come upon the seam of coal d, which the inclination of the strata may have brought within their reach, but which was unavailable in the country from e to f on account of its great depth. All the most valuable mines in the southern division of the coal-field are situated between the river Wear and the magnesian limestone which bounds the coal-field on the east; and a large proportion of the country west of the Wear, by this cropping out of the beds is occupied by barren strata of sandstone and shale, containing, occasionally only, a few small and unimportant seams, but no good workable beds of coal: and there is an enormous thickness of barren coal-measures beneath the low main coal, that crop out westward between Newcastle and the mountain called Cross Fell. It is probable, too, that along the whole west frontier of the triangular portion of the coal-field north of the

Tyne, one-half of the area is occupied by strata barren of workable coal.

No bed of coal is uniformly good throughout any great extent the high main coal is for many miles so deteriorated in quality, and so mixed up with stone, that it becomes worthless in many places. The coal seams worked in this field vary from eighteen inches to fourteen feet in thickness; but in the thick seams there is always a considerable portion of such bad quality as not to be saleable at a profit; and the best quality is seldom more than about six or seven feet thick. Throughout the whole of this field the best coals are those in the superior part of the series of strata of which the formation is composed. The best beds are those called by the miners the High main and the Low main.

The mode of working coal-mines varies in different parts of the country, partly on account of the situation of the seams of coal in the ground, and partly on account of customs peculiar to the spots. That which we are about to describe is the method usually adopted in the Newcastle coal-field; the chief sources of information on the subject are contained in the evidence given before the Committees of the Houses of Lords and Commons in 1829 and 1830, by Mr. Buddle and Mr. Taylor, eminent engineers or coal viewers, and of large experience in the north of England collieries.

No instances occur in this country of beds of coal lying so near the surface that they can be worked in open day like a stone quarry, nor are they often met with in the side of a hill, so that the mines can be pushed forward in a horizontal direction. When, therefore, a coal-field is to be won, as it is technically called, that is, when the coals are to be taken out, the first step is to sink a perpendicular circular shaft like a great well, in order to get at the coal, and by which the miners or pitmen descend, and the coal is brought to the surface. The sum required for winning a field of coal, that is, the coal under a certain portion of land marked out on the surface, is some. times so considerable, and the risk of failure so great, that very few individuals venture upon it on their sole account. They are usually won by a company, called adventurers, who take a lease from the proprietor. On the river Tyne there are only five proprietors, out of the 41 collieries, who work their own mines, and on the river Wear there are only three out of eighteen collieries; all the rest are in the hands of lessees or adventurers. The capital is raised by shares, often of small amount, and being transferable are constantly in the market. Collieries vary exceedingly as to the amount of capital required to win them, the difference being so great as from 10,000l. to 150,000l. One of the difficulties in sinking a shaft is passing through quicksands; another is the immense quantities of water which are met with in certain parts of the stratification, generally within 40 or 50 fathoms from the surface, which is always dammed back by a tub. Mr. Buddle mentions a shaft in which he had to apply 40 fathoms, that is, 240 feet of cast-iron tubbing. One shaft is not sufficient, another being required for drawing up the water and for ventilating

the mine.

The depth of the mines is very various; in one place near Jarrow, about five miles from the mouth of the Tyne on its southern bank, the High main coal of the Tyne is found within 42 feet of the ground, and the same coal lies under Jarrow Lake more than 1200 feet from the surface. This great depth is not reached by one perpendicular shaft, but a shaft and steam-engine underground, with descending inclined planes. A great improvement was made by this erection of steamengines to be worked in the pits underground, and which first took place in 1804.

The pit having been sunk to a sufficiently thick seam of coal, the process of excavating is begun by cutting out the coal laterally in galleries. In the Newcastle mines large masses of the coal, named pillars, are left to support the roof, at short intervals; but in Staffordshire the whole of the coal is taken away, and the roof of the mine is suffered to fall down, care being taken to support it so far as not to endanger the safety of the

THE MINERAL KINGDOM.

workmen. One set of workmen is employed in digging out the coal, and another in removing it to the bottom of the shaft, from whence it is drawn up by machinery to the surface. The work of the miners is very laborious, especially where the seams are so thin as to prevent their being in an erect posture.

In many collieries, after the whole of the coal has been got out in the ordinary way of working, they gradually cut away a part of the pillars of coal which have been left at intervals for the support of the roof, substituting props of timber; and sometimes the whole of the pillar may be taken awaywithout the roof falling in so as to impede the workmen in When the whole of the coal has been other parts of the mine. excavated and the roof does not fall down, vast empty spaces or wastes are left, which very generally after a while become filled with water, to the great danger of the adjoining collieries.

The chief accidents to which collieries are exposed, besides that of the roof and floor coming together by the pressure over the places where the coal has been worked out, are inundations of water, and explosions of gas. The quantity of water which of flows into the mines is sometimes enormous, and the expense drawing it off by pumps worked by steam-engines is one of the heaviest charges of a colliery. Mr. Buddle states, that in one with which he is connected, they draw eighteen times the weight of water which they do of coal. It very often happens that a mine is drowned by an accidental opening into an old working filled with water.

But of all the accidents to which coal-mines are exposed, the explosions of inflammable gas or fire-damp are the most frequent, and by far the most calamitous in their consequences. All coal, even the charcoal-like variety called anthracite, appears to contain, in its natural state while underground, a considerable quantity of free uncombined gas which it parts with when exposed to the air, or when it is relieved from great superincumbent pressure. The gas is evolved from the coal in great quantity at the ordinary temperature of mines; and instances have been known of explosions on board of ships laden Coals lying deep give out more gas with fresh-worked coals. than those near the surface, because there are openings at the surface by which it escapes; but in the deep mines it cannot have such an outlet, and therefore it accumulates in all the fissures of the stone above the coal, and this sort of natural disThe fissures of the roof are tillation is constantly going on. in some places very great, and there are sometimes miles of communication from one fissure to another; they may be considered as natural gasometers, and having no outlet, and the process of distillation constantly going on, the gas becomes accumulated in them in a very highly condensed state, the degree of condensation depending on the thickness of the surrounding rock, and the quantity poured in. In the course of pursuing the workings the miners sometimes cut across one of those fissures, or approach so near to it, that the intervening rock becomes too weak to resist the elastic force of the compressed gas; it gives way, and then, in either case, the gas rushes out with immense force. These blowers, as they are in a called, emit sometimes as much as 700 hogsheads of gas minute, and continue in a state of activity for many months together. Sir James Lowther found a uniform current of gas in one of his mines for two years and nine months.

This gas, in the state in which it issues from the coal, burns with a bright flame, like ordinary artificial coal gas; but when united with a certain proportion of the air of the atmosphere, the whole volume of air, upon the approach of a flame, suddenly catches fire, and goes off like gunpowder, with a tremendous explosion. If there be more than one volume or bulk of the inflammable gas to fourteen of atmospheric air the mixture is explosive, and must not be approached with a naked flame. Great pains are taken to ventilate the mines so as to free them from this foul air, by large fires kept constantly burning at the mouth of the ventilating shaft, aided very often by air-pumps worked by steam-engines to quicken the draft. One mine is described by Mr. Buddle as generating so much

gas as to require a supply of 18,000 cubic feet of atmospheric
Men can
air in a minute to keep it in a safe working state.
continue to work and breathe in an explosive mixture of the gas
without feeling any material inconvenience; and formerly
such places were approached by making use of what were
called Steel Mills, to give light. This machine consists of a
small wheel of steel, of six or seven inches diameter, moved by a
little toothed wheel with great velocity, and by holding a piece
of flint to the steel, a stream of sparks is given out. Although
in the day the light appears very feeble, in the darkness of the
mines it is strong enough to enable one to write by it; but the
use of the steel mill is not free from danger of explosion in
That contrivance has, however,
certain mixtures of the gas.
been now completely set aside by the important discovery of
Sir Humphry Davy, the SAFETY-LAMP.

Davy instituted a long series of experiments on the nature
of the fire-damp, and on the proportions with which it must he
mixed with atmospheric air in order to become explosive. He
found that, in respect of combustibility, the fire-damp differs
most materially from the other common inflammable gases, in-
asmuch as it requires a far higher temperature before it can be
set on fire; an iron rod, at the highest degree of red heat, and
at the common degree of white heat, did not inflame explosive
mixtures of the fire-damp, and an
explosion only took place when a
flame was applied. He further
made the important discovery, that
flame will not pass through a tube
with a very small bore; and, guided
by this principle, he was ultimately
led, through a train of ingenious
experiments, to the construction of
an instrument which has saved the
lives of hundreds, and which has
rendered a large extent of property
productive that the proprietors were
unable to turn to any profitable
account. The accompanying is a
representation of "THE DAVY," as
the safety-lamp is now called by
the miners.

The construction of it is very
simple:-A. is the lamp in which
oil is used; and there is a small,
bent wire, moved by passing
smoothly through a hole in the
bottom, for the purpose of trim-
ming the wick. B. is a cover of
fine wire-gauze, which is fastened
upon the lamp, and generally A
locked to prevent the miners taking
it off; and this cover is strength-
ened by upright wires, twisted at
the top to receive a ring for carry.
ing the lamp. Some recent im-

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provements have been lately introduced by the application of reflectors, for the purpose of concentrating the light. When the lamp is carried into a part of the mine which is highly charged with fire-damp, the flame of the wick begins to enlarge, and the air, if it contain so much of the inflammable gas as to be highly explosive, takes fire as soon as it has passed through the gauze, and then burning within the lamp extinguishes the flame of the wick by cutting off all communication with the pure air of the atmosphere. Whenever this appearance is observed the miner must instantly withdraw; for although the flaming gas within the lamp cannot pass through the gauze so as to set fire to the explosive mixture outside, it makes the wire gauze so hot that it would very speedily be wasted, and a hole, large enough to let the flame come out, would be burned.

The annual consumption of coals in Great Britain is enormous; but there are no means of ascertaining the amount with

anything approaching to accuracy. In the evidence before the Committees of the Lords and Commons, in 1829 and 1830, we have some calculations by Mr. Buddle and Mr. Taylor. Mr. Buddle says, "The calculation which I have made of the consumption of England and Wales is as follows:-manufactories 3,500,000 London chaldrons; household consumption, 5,500,000, making 9,000,000 in all consumed from inland collieries: the quantity sent coastwise, on both sides of the island, is 3,000,000; together 12,000,000 chaldrons." As a London chaldron is nearly 27 cwt., that quantity is equal to about 16,200,000 tons weight.

Mr. Taylor's estimate of the consumption of coal in Great Britain is given in the following form:

The annual sale of coals carried coastwise, from
Durham and Northumberland, is
Home consumption, say one-fifth.....

Tons.

3,300,000 660,000

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Total tons, exclusive of foreign exportation.... 15,580,000 The export of coals from the Tyne and the Wear amounted, in 1828, to about 3,200,000 tons, and the consumption on the spot to about 660,000 tons. In 1838 the quantity exported by sea from Newcastle alone was 3,004,953 tons.

So vast a consumption leads to the inquiry, "what, at this rate of annual excavation, will be the probable duration of this coal-field?" This question occupied a great deal of the attention of the Committees of both Houses of Parliament, already spoken of, and there was a very wide difference in the answers which they received. Mr. Taylor being asked by the

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There remain....6,046,320,000

Dr. Buckland, however, considers the estimate of Mr. Taylor much exaggerated. Mr. Sedgwick is also of opinion that Mr. Taylor's estimate is too great. He has assumed that there is a continuous thickness of 12 feet of workable coal over the whole area of 732 square miles; but all experience, both of this coal-field and of every other, is unfavourable to this assumption, for not only are the coal-seams extremely variable in thickness, but they are equally so in quality, as we have already shown. Mr. Bakewell, in his "Introduction to Geology," calculates that the coal-field now under consideration will not last above 360 years. All these calculations, however, have reference only to the best qualities of coal,-to those which can be raised at an expense sufficiently low to enable them to be sold at a remunerating price in competition with other coals.

It appears to be very clearly made out that all those parts of the country which are now supplied with fuel from the Northumberland and Durham mines will continue to enjoy that advantage for the next 400 years; and there is still a store

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in reserve far greater than there was in the whole of the North of England field before a single fire was lighted by its produce. This extensive repository is in the coal-field of South Wales.

The geographical position of this vast deposit of the coalmeasures will be seen by the annexed Map. It lies in a great basin of the carboniferous limestone (O, Diagram, p. 235) which rises from under the coal strata nearly all around the limit of the coal-field. In a part of Pembrokeshire the limestone is wanting, and the coal strata rest upon slate (Q) which is inferior to the limestone, and, near Narbeth, they are in contact with the old red sandstone (P) which lies between the slate and the limestone. In a part of the southern boundary in Glamorganshire the coal-measures are separated from the limestone by a detached deposit of strata of posterior formation to them, and therefore lying upon them, viz. new red sandstone (K), and lias limestone (I. f).

The coal-measures within this limestone basin lie in a trough shape, being deepest towards the middle, and rising up towards the outer limits, the ends of the several strata cropping out, that is, appearing successively at the surface. They do not, however, form one uniform sweep or inverted arch; for there has been a partial upheaving of the strata, so that a section across the field from Bridgend, due north, would present the following appearance :—

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There are thus two basins, the one to the north, the other to the south of a high ridge a, which runs from Aberavon half a mile north of the Avon by Cefn Eglwysillan, two or three miles north of Caerphilly, a little beyond which it disappears. In the northern basin, which is by far the more extensive, the strata are much less inclined than in the southern basin; for in the former the dip of the strata is generally under 10°, while in the latter it is often 45° and upwards. The whole coal-field is traversed by dikes or faults, generally in a north and south direction, which throw all the strata from 300 to 600 feet up or down. On the western termination of the basin, in St. Bride's Bay, the strata are both vertical and twisted in every possible direction.

Mr. Conybeare makes three great divisions of the seams in this coal-field-the lower, middle, and upper series; and he assigns to them, respectively, the average thickness of 35, 15, and 10 feet, making altogether 60 feet of workable coal. Martin, who described this coal-field, makes them amount to 95 feet; and Mr. Conybeare thinks that Martin does not overstate the amount, provided all the seams be taken into the account. But Mr. Conybeare's calculation only includes the workable coals, and he considers that those seams cannot be worked with profit where it is necessary to go lower than 1200 feet, for beyond this the expense of drainage, &c., becomes enormous. Keeping the same considerations in view, Mr. Conybeare makes the following estimate of the area occupied by the coal

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times that amount, we have a supply of good coal, which, at the present rate of consumption, would last above 3000 years. The coal-fields of Scotland, although very productive, are confined to a limited space. Nearly all the valuable mines are in the Low Country, between the Highlands on the north and the range of slate mountains which run in a north-east and south-west direction across the island in the South of Scotland. The capital is very abundantly supplied with excellent qualities of coal brought from a distance of only a few miles, and delivered in Edinburgh at from 9s. to 12s. per ton. Glasgow is surrounded with collieries, and is supplied at even a cheaper rate than the capital; and to this profusion of fuel not only Glasgow but Paisley, and the neighbouring great manufacturing towns, owe, in a great degree, their origin and prosperity. The mines in the counties of Fife and Clackmannan also produce very fine qualities of coal.

The coal formation of Scotland is found in the county of Antrim, on the opposite coast of Ireland. The collieries of Ballycastle, on the north coast of Antrim, formerly sent from ten to fifteen thousand tons to market yearly, but they are now greatly fallen off. In the eastern part of the county of Tyrone, at Coal Island and Dungannon, a coal-formation occurs associated with that variety of limestone which is usually found underlying or alternating with the coal-measures in Scotland and England.

Coal has been discovered in 17 counties of Ireland. The coal district of the province of Munster, according to Mr. Richard Griffith, is greater in extent than any in England. It extends over a part of the county of Clare, over a considerable portion of the counties of Limerick and Kerry, and a large part of the county of Cork. But none of the coal-beds of this province, with the exception of those in the county of Clare, belong to the same geological period as the coal-fields of England and Scotland: in place of lying above the carboniferous limestone (O, Diagram, p. 251), they lie under it, and are interstratified with the old slate rocks (A), the lowest in the whole series of the secondary strata. The quality of the coal too is quite different from either the Euglish or Scotch coal, being that variety called anthracite, which burns without flame, and approaches to the nature of charcoal. It is chiefly used for burning the limestone of the adjoining districts; and the most considerable collieries, those of Dromagh, have yielded 25,000 tons per annum, at from 10s. to 15s. per ton. The district of Clare belongs to the true coal. measures (M), but they are chiefly the shales, sandstones, and sandy slates, coal being of very rare occurrence, as far as discoveries have yet been made, and when found it is of very indifferent quality. Mr. Griffith is of opinion that coal of a bituminous quality is very extensively distributed over the eastern part of the province of Connaught, particularly in the counties of Leitrim and Roscommon. In the province of Ulster, besides the collieries in the counties of Antrim and Tyrone, coal has been met with in the counties of Fermanagh, Monaghan, and Cavan, but not to any great extent. The province of Leinster contains the true coal-measures, lying above the carboniferous limestone, in the county of Carlow, and in Queen's County, and in the county of Kilkenny, from whence it stretches some way into the county of Tipperary. The great deposits are around Castlecomer in Kilkenny, and Killenaule in Tipperary, and both these have been extensively worked; but, according to Mr. Weaver, in his account of the Killenaule district, the coal of that field, and of the other portions of the Leinster coal-tract, is wholly of the nature of anthracite, and of a thin stratified structure.

Coal is found in many parts of the continent of Europe. One of the most considerable deposits is that of Belgium, where, in the province of Liege, the coal-formation extends from Thon near Namur to the confines of the province of Limburg, along the Maas for 33 miles, and with a breadth of about 8 miles. Continuing in a north-east direction from Liege, we find another coal-field between Aix-la-Chapelle and Dusseldorf, the principal collieries being in the neighbourhood

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