Great Britain. Near which furnace the author discovered many new coal-mines, ten yards thick, and iron-mines underneath, which coal-works being brought into perfection, the author was by force thrown out of them, and the bellows of his new furnace and invention by riotous persons cut in pieces, to his no small prejudice, and loss of his invention of making iron with pit-coal." He informs us, further on, that this had been "of late a mighty woodland country;" and proceeds, "Now if the coals and ironstone so abounding were made right use of, we need not want iron as we do, for very many measures of ironstone are placed together under the great ten yards' thickness of coal, and upon another thickness of coal two yards thick, not yet mentioned, called the bottom coal or heathern coal, as if God had decreed the time when and how these smiths should be supplied, and this island also, with iron; and most especially that this coal and ironstone should give the first and last occasion for the invention of making iron with pit-coal, no place being so fit for the invention to be perfected in as this country for the general good, whose lands did formerly abound in forests, chases, parks, and woods, but exhausted in these parts." Many subsequent attempts with furnaces supplied with air from leathern bellows, worked by oxen, horses, or human labour, were failures, for additional resources from mechanical powers were needed before the blast could be rendered sufficiently powerful to enable pit-coal to be applied to the smelting of iron. The required assistance was at length provided in the steam engine, improved and perfected within a few miles of one of the great coal and ironstone districts.

The beds of coal in a coal-field, though of a considerable number, are far less numerous than the alternating strata of sandstone, and shale, called rock measures, and far less in the aggregate thickness. At Anzin, near Valenciennes, a pit less than 100 yards deep passes through 50 layers of coal, small and great; at Liege 61 have been ascertained; the single mountain of Duttweiber, near Saarbruck, includes 32; at Newcastle the Killingworth pit, within 230 yards, traverses 25. The total thickness of the coal in the English and Scottish fields is stated to be from 50 to 60 feet, divided into 20 or more beds, which vary in thickness from a few inches to six feet, and alternate with from 20 to 100 times as great a quantity of rock measures. Mr. W. Forster, in the following table. represents the alternations of the coal and rock measures in the Newcastle district, with the thickness of each :

Mr. N. J. Winch gives the following enumeration of the different strata passed through in Bigge's Main Colliery in the Newcastle coal-field, which shows the relative preponderance of the rock measures over the seams of coal in thickness:

1. From the surface of the ground they sunk through clay to the depth of

2. Through sandstone from thence

s. They then came upon the first seam of coal, but which had only a thickness of

4. From this seam to the thick bed called the High 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

5. The High Main coal of the Tyne had here a thickness of

6. From this seam they sunk further through 52 beds of sandstone and shale, varying from 5 inches to 84 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

82 0

And giving a total depth of

1157 11

Thus 125 different strata were passed through, only 32 of which were seams of coal, and only 19 of these were capable of being profitably worked. The thickest bed of coal in the Newcastle district, the High Main of the Tyne, does not exceed 6 feet; this is exceeded by a bed in the Yorkshire coal-field, near Barnsley, which is 10 feet; but this is again far surpassed by the south Staffordshire or Dudley coal-field, which contains seams from 30 to 45 feet in thickness. In this latter case, however, the enormous thickness seems to be rather made up of a number of beds divided by thin layers of clay slate, than one continuous stratum. In general, except near to the surface, a seam of coal will not pay the expense of working under a thickness of two feet.

The position of the coal measures is occasionally very highly inclined, but commonly they lie at a less angle, and often, as a whole, exhibit the appearance of a huge trough, or basin. The next engraving represents this construction, a section of the Bristol coal-field, extending from the Mendip Hills to the north-west of Bath, a distance of about twenty miles. The regular basin-shape given to the strata in the section is not indeed that which a perpendicular cutting into the ground of the district would expose, for many dislocations and disturbances would appear; but the general arrangement of the coal measures of that locality, and in other places, shows the concave bendings indicated. This disposition is not peculiar to the coal series, but belongs more or less to all formations where underlying strata or igneous rocks project in hills and mountains, though it has been more particularly remarked in the carboniferous system, from that having been more attentively searched for its important product. It is obviously due to an upheaving subterranean agency, to the action of which the series of coal seams has been variously

exposed, tilted up on the sides by the obtrusion of subjacent masses.

This basin-shape is of immense utility, since it has brought all the layers of the formation near to the

Mendip Hills.

surface, and thus placed them within reach; for had they followed a uniformly inclined course without interruption, the lower seams would have sunk to depths inaccessible to the art of man. The preceding section very clearly points to the cause of the concave form of the coal-beds. It shows also that the carboniferous deposit must have been laid down before the elevation of the Mendip Hills, and that the horizontal strata overlying the coal, belonging to the saliferous and oolitic systems, must have been formed after the disturbance took place, since they exhibit no symptoms of participation in it. Besides the proof of disturbance afforded by the concave form of the coal strata, they

Fault in Coal-field,

have been splintered and broken in various directions, by the same tremendous power to which their general contour is due, and hence the slips, faults, and dykes which the miner encounters in traversing a single stratum. The simplest form of a fault, or dyke, is shown in the engraving, the corresponding beds on each side being slightly thrown out of their level, the fault itself having no great breadth. In many cases, ¦

however, faults have a considerable width, one of 22 yards occurring in Montagu colliery in the Newcastle coal-field; and instead of the beds thus broken presenting only a trifling change of level, the difference is often enormous. In the Newcastle coal-field a fault occurs termed the "ninety fathom hitch," the strata on the opposite sides deviating from a common line to that extent. A fault at Sheriff-hall, in the vale of the Esk, in Mid Lothian, throws the strata out of the line of stratification no less than 500 feet, and in that locality 120 ascertained dislocations occur. They abound also in the coal-fields of Fife and Clackmannan, causing divergences to the extent of from between 500 and 1200 feet. The extraordinary energy of the dislocating power is sufficiently proclaimed by the fact of massy beds being fractured, and the broken parts separated from each other, by such intervals as these, either through the elevation of the one or the subsidence of the other, for it is impossible to say which has happened. Faults are sometimes repeated several times within a very short distance, each involving the displacement of strata. However

seriously these derangements interrupt for a time the work of the miner, they are not without their use, acting sometimes as valves by which the water of a mine is drained off, or when filled up with compact matter, they serve as floodgates arresting its course, and preventing its access to deposits which it might otherwise inundate.

The coal-beds exhibit immense disturbances from the eruption of igneous rocks, the members of the trap family - greenstones, clinkstones, and basalts-which are associated with them in disrupting, overlying, and interstratifying masses, charring the coal in their neighbourhood, and variously converting it into coke, anthracite, and plumbago. The South Staffordshire coal-field is invaded by a picturesque range of basaltic hills between Dudley and Rowley Regis, and by other eruptions of trap which fill up dykes and faults occurring in the strata. The manner in which the beds of coal have here been disturbed and broken through by protruding plutonic masses, is illustrated in the two sections from

a, Lower new sandstone; b, thick coal seams; c, thin seams spreading out beneath the seams; d, silurian rocks on which they rest. Sir R. Murchison; the one an imaginary sketch of its appearance while a depositary undisturbed by the subterranean forces; the other exhibiting its present shattered aspect as the result of their action. Analogous disruption and dislocations of the coal by trap rocks appear in almost every field.

a, Lower new red sandstone; b, b, coal measures; c, thin coal and ironstone; d, silurian rocks; e, trap rock.

The working of the coal measures is one of the most severe and dangerous departments of human labour, even when under the most enlightened and humane superintendence, and with capital sufficient to command the application of steam-power as extensively as it can be employed; but when under the management of a needy or grasping owner, a colliery is equally degrading to humanity and perilous to life. In coal mines of this latter description females were employed at the windlass and at labours still more revolting -a spectacle which legislation has in the present age laudably abolished. The master difficulty, however, of many coal-mines, which no law can touch, and which defies the power of capital and the contrivances of humanity, arises from the thinness of the coal-seams, which become the subterranean roadways after the mineral has been extracted, and the distances to which these lateral passages extend from the main shaft, together with the depth below its bottom to which excavation leads. They cannot be traversed except in an unnatural and constrained posture, nor could their capacity be enlarged without an

Every pit which has been worked any length of time contains a number of these excavated seams, one above another, connected by trap stairs, all lying below the

bottom of the shaft of the mine, to which the coal has to be carried. The height ascended, with the length of the lateral passages, is often a journey equal to the ascent of St. Paul's, but far more laborious, owing to the burdens borne by the coal-bearers. Sometimes the subterranean highways, instead of being connected by a trap staircase, are severally reached by a "turnpike stair," a gradually ascending, spiral, unrailed road. Besides the exhausting nature and the dreary scene of their toils-plying with blackened arms the pickaxe, a hundred fathoms deep below the surface of the soil, in damp and darkness which a few flickering lamps serve but to render visible-peculiar dangers threaten habitually the mining population, from the possibility of the roof of their subterranean workshop falling in upon them, or the explosion of the inflammable gas evolved from the coal, through contact | with an unguarded flame.

In no part of the world are the coal measures, with the other members of the carboniferous system, so extensively developed, within the same area, as in the British islands. Leaving out of sight the great beds in the lowlands of Scotland, and in Ireland, there are in England and Wales the following fields, the arrangement of which is adopted from Conybeare and Phillips :

COAL DISTRICT NORTH OF THE TRENT, OR GRAND PENINE CHAIN.

1. Field of Northumberland and Durham, stretching from the river Coquet on the north to the Tees on the south, a distance of fifty-eight miles, by a breadth, at the greatest, of twenty-four.