Between Abberford and Halifax it is 25 miles in breadth, but it decreases greatly in breadth as it passes through Derbyshire, and terminates at Woollerton, near Nottingham. The thickest bed of the Yorkshire coal is worked near Barnsley. The greater part of the coal of this county is required to supply its numerous population, and its important manufactures of woollen and iron. A part of the coal of Derbyshire is carried by canals to the midland counties. Ironstone, of a good quality, is abundant in this coal district. South-west of Derbyshire there are a few small coalfields, in Leicestershire and Warwickshire, near Ashby-de-la-Zouch, Tamworth, Atherstone, and Coventry. The main coal of the Ashby-de-la-Zouch coalfield, at Ashby Wolds, is 13 feet thick. It is worked, in the lowest part, at the depth of 224 yards.

The Coventry coalfield is the most southern situation in which coal has been discovered in the midland counties.

On the north-west side of England we find a valuable small coalfield, extending from Maryport to Whitehaven, containing seven beds of good coal in one mine it is worked at the depth of 298 yards, and in some mines, the workings have been carried on under the Irish Sea. A considerable quantity of coal is exported from this district to Ireland.

The Lancashire coalfield is separated from that of Yorkshire by a range of lofty hills, extending from near Colne to Blackstone Edge, and thence to Ax Edge, in Derbyshire. The coalfields of Lancashire commence near the western side of this range, the strata dip westward, but are more broken and deranged by faults than the Yorkshire coal strata. The principal beds of coal are one of 6 feet in thickness, and a lower one, called the three-quarter bed.

The Lancashire coalfield runs nearly due north from Macclesfield to Oldham, at the feet of the range of hills above mentioned, but in this part it is scarcely more than 6 miles broad: from Oldham, it extends westward to Prescot, near Liverpool, and northward to Rochdale and Colne. The ample supply of fuel which this coalfield yields for the use of the cotton manufactures of Manchester and its vicinity, may be regarded as contributing, in an eminent degree, to their unrivalled prosperity. In the north part of the county of Lancaster there is a small coalfield, on the southern side of Ingleborough, but it is of little importance. South of the great Lancashire coalfield there is a small but valuable coalfield, near Newcastle-under-Line, in Staffordshire it is about 10 miles in length from north to south, and from 5 to 7 miles in breadth, and supplies the potteries of this district with potters' clay and fuel. There are numerous beds of coal in the different parts of this coalfield, varying in thickness from 3 to 10 feet.

A little to the south-east of the pottery coal district, there is a small coalfield, near Cheadle, but it is of little importance.

The coalfield of Wolverhampton and Dudley, in Staffordshire, is the most valuable one in the central parts of England; it contains the thickest bed of coal in South Britain, the main coal varying from 30 to 45 feet in thickness, beneath which are several beds of coal from 3 to 4 feet in thickness; and several beds of coal occur over the main coal. The tract of country containing the main coal is estimated by Mr. Keir to be 7 miles in length, and about 4 miles in breadth; but, beyond this, an equal space northward is occupied by thinner beds of coal. The value of the 30 feet bed of coal is not so great as might at first appear, though it is of a good quality, and within the reach of the miner. So much labour and expense is required to support the roof, when the coal is worked away in any part, and so much waste coal is left in the mine unavoidably, that it is calculated that one bed of good coal of 10 feet thickness, with a firm roof, would yield more profit to the miner, per acre, than the 30 feet bed of main coal. The coal of this district rests upon the lower transition limestone, so celebrated for its fossil trilobites. This limestone is singularly raised and bent, at Dudley Castle Hill and Wrens-nest Hill: the upheaving and bending of the strata has probably been effected by the protrusion of basaltic rocks, of which several make their appearance in the vicinity: the basalt is provincially called Rowley ragg.

The Dudley coalfield is about 60 square miles in surface, the 30 feet coal occurs on the southern part of the field; it may be seen cropping out between Wrens-nest Hill and Dudley, preserving a compact form. Minor beds of coal, when they rise to the surface, are generally decomposed, forming what is called coal smut. There are two valuable beds of ironstone, of considerable thickness, extensively worked in this district, on which there were about 100 iron furnaces in full activity in the year 1827. This coal district, in proportion to its size, may be regarded as the most valuable mineral repository in Europe. Besides the immense consumption of coal in the various iron founderies, forges, and other numerous manufactories in Birmingham and the adjacent country, large quantities of coal are sent by the canals into the neighbouring counties.

In Shropshire and Herefordshire, there are a few small coalfields ; the principal one, at Coalbrook Dale, 10 miles east of Shrewsbury, is 6 miles in length, and about 2 miles broad. Coalbrook Dale, some years since, was celebrated for its iron furnaces and founderies, but, owing to the superior quality or cheapness of the Welsh iron, they have recently been closed. The Clee Hills, near Ludlow, contain

some detached coal basins. The summits of these hills are capped with basalt; and a mass of basalt cuts through the most southern of them There is a narrow coalfield on the north-eastern border of Wales, extending from Mostyn, in Flintshire, to the entrance of the valley of Llangollen, in Denbighshire: the coal strata are separated from mountain limestone by coarse millstone grit.

The coalfield of the Forest of Dean, on the western side of Gloucestershire, is about 10 miles in length, and 6 in breadth; and is a very valuable repository of this useful mineral. The several beds of coal, and the strata of sandstone that accompany them, are arranged in a basin-shaped concavity, resting on millstone grit and mountain limestone. It is the most perfect type of what geologists call a coal basin, of any in Great Britain.

The most southern coalfield in England is situated on each side the river Avon in Somersetshire, and the South of Gloucestershire; it is about 25 miles in length, and 6 in breadth; but it is covered in many parts by beds of red marl and sandstone, and lias limestone. The deepest coal mine in England is stated to be at Radstock, near Bath: it is 409 yards from the surface. There are several small seams of coal in this coalfield, none exceeding about 3 feet; they would scarcely be deemed worth working, were it not for the scarcity of coal in that part of England.

We have now noticed all the repositories of coal in England and Wales deserving attention, except the great coal basin of South Wales, which may be considered the most important coalfield in Great Britain, containing a quantity of coal sufficient to supply its inhabitants for 2,000 years after most of the other coalfields are exhausted. The coal strata extend about 100 miles in length, from St. Bride's Bay, in Pembrokeshire, to Pontypool, in Monmouthshire; but they are broken into by Caermarthen Bay. In Pembrokeshire, the breadth is only about 5 miles, but they cover a great part of Glamorganshire. The extent of surface is about 1,200 square miles. The strata are arranged in a kind of trough, and dip down on each side, north and south, towards the centre of the field, or rather to the central axis of the field, along a line drawn from St. Bride's Bay to Pontypool. The deepest part of this coalfield is near Neath. The coal is there 700 fathoms below the highest parts of some of the beds. There are 23 workable beds of coal, the average thickness of which is 95 feet. There are 12 beds of coal, varying in thickness from 3 to 9 feet, and 11 minor beds, varying from 18 inches to 3 feet in thickness. The coal is of different qualities, in different parts of the district; that on the western side being chiefly dry coal, and on the eastern side, bituminous coking coal, suited for the smelting of iron. Many

of the beds of coal and ironstone occur at a great depth from the surface, but the country being intersected by valleys that run north and south, and cut through and lay open the lower beds, the miner can work them at a small expense, by driving levels into the sides of the hills. From the great quantity of ironstone, and the facility with which it may be obtained, iron can be produced at a lower price at Merthyr Tydvil, and other parts of this district, than in Staffordshire, or, we believe, in any other part of Great Britain.

It has been before stated, that a waving line might be drawn from Exmouth to Stockton-on-Tees, east of which no good mineral coal is found; very near the same line, a lofty range of calcareous hills may be traced through England, but with some interruption. On the south side of the Vale of Severn, in Gloucestershire, they are well known as the Cotswold Hills, and the range terminates in the Cleveland Hills, on the east side of the North Riding of Yorkshire. Between this line of hill, and the transition and coal districts before described, the surface of England is covered by secondary formations, chiefly consisting of red marl and sandstone, called by geologists the new red sandstone, to distinguish it from the red sandstone which sometimes occurs below the coal formation; whereas this new red sandstone, where it occurs with coal strata, always is found above them.

The new red sandstone is regarded as the lowest of the secondary formations that succeed the coal strata in an ascending series. The coal strata are often much bent or inclined, but the strata of red sandstone are nearly horizontal; hence it appears that the latter were deposited after the coal strata, and the transition rocks, had been subjected to the action of the disturbing causes, by which the beds were inclined or bent. The relative position may be conceived, by imagining a series of books to be inclined from the perpendicular, and another series to be laid flat over the inclined edges of the former.

The secondary formations of England may be enumerated in the following order, without entering into any of the numerous subdivisions, which it would be useless to introduce in a general outline. We shall begin with the lowest. In some situations the thickness of the different formations has been ascertained, but this thickness is very variable in distant parts of the same formation.

Red sandstone and red marl.

Magnesian limestone, subordinate to red sandstone.

Lias limestone and clay.

Oolitic limestone, with beds of sand, sandstone, and clay.

Lower and upper green sand, with clay.

Lower and upper chalk.

The new red sandstone and marl is most frequently of the colour which its name implies; its prevailing mineral character is siliceous, but it comprises a great variety of beds, from a coarse conglomerate, composed of large fragments, to a fine-grained sandstone. A series

of strata of magnesian limestone, of considerable thickness, occurs between the lower and upper beds of the new red sandstone, forming a narrow range of low hills, extending from Sunderland to Nottingham.

In the upper part of the red sandstone formation, there are thick beds of red and variegated marl, in which are rocks of gypsum and irregular masses of rock salt. The red marl forms some of the most productive soils in England. The new red sandstone and red marl occupy a considerable part of the midland counties, and extend on the western side of England, into Lancashire, and on the eastern side, into Yorkshire. Rock salt has hitherto only been found in Cheshire and Worcestershire, but numerous saline springs, in different parts of the new red sandstone formation, indicate the presence of this mineral. The upper bed of rock salt, in Cheshire, was discovered, about 150 years since, in searching for coal: it is about 40 yards below the surface, and 26 yards thick, and is separated from a lower bed of salt by a stratum of argillaceous stone, 10 yards thick. The lower bed has been sunk into 40 yards. At Northwich, the rock salt extends in a direction from north-east to south-west, 1 mile; its farther extent in that direction is not ascertained. The breadth is about 1,400 yards. In another part of Cheshire there are 3 beds of rock salt, the lower of which has been sunk into 25 yards, but has not been cut through.

The rock salt of Cheshire is sometimes coloured red, by an admixture with a small portion of oxide of iron; the colourless, transparent specimens are nearly pure salt, with scarcely any water of crystallisation. There are also numerous salt springs in Cheshire, containing 25 per cent. of salt.

At Droitwich, in Worcestershire, the existence of rock salt has been proved by boring, but all the salt is procured by evaporating the water, which is nearly saturated with it.

Lias limestone and clay may be traced at the feet of the Cotswold Hills, and along the whole range, from Lyme, in Dorsetshire, to Whitby, in Yorkshire. It rarely attains an elevation of 200 feet. It consists chiefly of dark argillaceous limestone, which contains iron, and forms, when bound, a good water-setting lime. The most conspicuous section of the lias beds may be seen at Lyme, forming cliffs on the coast, remarkable for the abundance of fossil organic remains, particularly of large saurian animals partaking of the structure of