was first introduced into London it has gradually extended, and become quite as important to the metropolis, where it was at first prohibited, as to any other part of the realm. In 1829, the London market took up 2,018,975 tons, conveyed (including repeated voyages) in 6,992 ships. In 1858 this quantity had increased to 4,447,191 tons. The coal trade for a long time was kept down by the duties which were levied upon it; an export duty was formerly levied, amounting to 17s. the chaldron, or 6s. 5d. ton upon large, and 1s. 8d. per ton upon small coal. In 1831 these duties were modified to 3s. 4d. per ton upon large, and 2s. upon small coal. In 1831 the coastways duty was repealed, and in 1835 all the other duties were taken off. Since then the coal trade has gradually and rapidly expanded.

In this gradual expansion of the mining interest, every aid which mechanical science offered has been laid under contribution. The invention of the safety lamp, by Sir Humphrey Davy, in 1815; and the simultaneous invention of the "Geordie," by Mr. George Stephenson, proved a great boon. In numerous instances works had been abandoned, with one third of the coal remaining, on account of the danger of explosion from using the naked candle; but, on the introduction of the Davy lamp, these pits were reopened, and afterwards profitably worked. This invention virtually added twenty or thirty per cent. to the workable area of the coal fields of the United Kingdom, and, in fact, of the world. Much good has also been effected by the improvements in the drainage of mines. The old wooden pumps would have proved quite inadequate to the drainage of many collieries, and consequently vast quantities of coal have been rescued from loss. And may we not anticipate that future discoveries in this respect will also virtually add to the coal bearing properties of a mine; the different improvements in working, &c., will all be the means of not only getting the coal more neatly, but also in obtaining more of it.

In conclusion, we shall devote a few pages to the description of the principal coal-fields of Great Britain and Ireland. In describing their geographical distribution, we shall follow the arrangement of Conybeare and Phillips: dividing them into--

I. The coal fields north of the Trent, surrounding the Great
Penine chain, and containing--

1. The coal field of Northumberland and Durham,

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2. That of Yorkshire, Nottinghamshire, and Derbyshire.

3. The coal field of North Staffordshire, sometimes called the Pottery coal-field.

4. The coal field of Manchester.

5. The coal field of Whitehaven.

II. The central coal district, comprehending the coal fields1. Of Leicestershire.

2. Of South Staffordshire.

III. The western district, subdivided into

1. The north-western, containing the coal fields of North Wales. 2. The western, containing those of the Plain of Shrewsbury, of Colebrookdale, and the Dee Hills.

3. The south-western, comprising the coal fields of South Wales, of the Forest of Dean, and of Gloucestershire and Somersetshire.

Although the coal fields of England are so insulated, often existing in basins, &c., there are many circumstances which render it exceedingly probable that they were once continuous, or nearly so, and that their separation has been caused by dislocations subsequent to their formation; some of them, as the coal fields of Durham, and Yorkshire, and of Lancashire, and North Wales, appear from the dip and strike of their strata to be even now united; although their junction is concealed by deposits of permian, and new red sandstone.

I. NORTHERN COAL DISTRICT.

1.-Coal fields of Northumberland and Durham.

This celebrated coal field extends from the mouth of the river Coquet on the north, nearly to the Tees on the south; occupying according to Mr. Buddle an area of 700 square miles. It is bounded by the sea as far as Shields on the east; beyond which there is a margin of a few miles from the sea; and it extends about ten miles west from Newcastle. South of Shields the surface is covered by a triangular area of magnesian limestone, the apex of which is on the northern bank of the Tyne, while the base extends from Hartlepool on the east, to Pierce bridge on the west. It was long maintained that no coal of workable quality was to be found beneath the cover of magnesian limestone; but, in 1821, through the persuasion of Mr. William Smith, the celebrated geologist, Colonel Braddyl was led to sink through it in search of coal, and the result has been the Great South Hetton Colliery and numerous others.

The rise of strata in this coal field is towards the west, and is seen in the valleys of the Tyne and Wear. There is every probability that the Northumberland coal field is in reality a synclinal trough, the eastern half of which is beneath the German Ocean; for, at South Shields, the beds rise towards the east. The total thickness of the measures in this district is about 2,000 feet; containing about 600 separate beds, and eighteen workable seams, comprising a total thickness of eighty feet. The most important seams of coal are the "high main," and the "low main ;" the first being six feet, and the second, seven feet in thickness. Between these, and distinct from each other about sixty fathoms, is the "bensham" seam, exceeding three feet in thickness, and the "yardcoal," of the thickness implied in the name. There are seven beds below the "low main," but they are of rather inferior quality. The largest is the "wickham street," six feet in thickness; and the lowest is the "brockwell," about three feet thick. The coal is generally very bituminous, and is supposed to be the best in the world for household purposes. There is very little ironstone in this district; but iron pyrites is abundant, disseminated through the coal. The best defined sandstone beds are the "grindstone," the "seventy fathom," and the "main post" beds; the first supplies excellent grindstones, and good building material; the other two beds lie below it, a good thickness of argillaceous strata intervening. The "main post" bed is most continuous, and always accompanies the "main" coal. The great denudations of the Tyne and the Wear are supposed to have destroyed an immense quantity of the most valuable beds of coal; but this destruction has been compensated by the complete exposure of all the contents of the coal fields, and the facilities thus offered for the discovery and working of many of the seams, and by the aid afforded to their cheap drainage by means of adits. This coal field is also much disturbed by faults and dykes, which are sometimes filled with sand and clay. The principal fault is from ninety to 130 fathoms perpendicular, and is regarded as a downthrow. It brings, however, into a workable position a second time, several important seams, cropping out near Newcastle. There is hardly a colliery in which several of these faults are not met with. When these faults are filled with clay, they serve to dam up numerous springs, and cause them to find

*Trimmer's "Geology."

vent at the surface. There is one fault which commences on the southern part of the Newcastle cold field, near Bishop Auckland, in Durham, and runs in an easterly direction through the secondary rocks of Yorkshire, being traceable for nearly sixty miles in a straight line. A stratum of sandstone occurs in this coal field, nearly five hundred feet below the surface, on which numerous fossil trees have been found standing erect, each from two to eight feet in circumference; their roots were found extending into thin layers of coal.

2.-Coal field of South Yorkshire, Nottinghamshire, and

Derbyshire.

The

This is another valuable and extensive coal field, closely allied in its character to that of Newcastle, and is perhaps a re-emergence of the same strata beneath the magnesian limestone. The strike of the strata, as in the Newcastle coal field, is from north to south; and their dip to the east beneath the magnesian limestone; their western outcrop is against the rocks of the millstone grit, which constitute the higher regions of the Penine chain. It occupies an area extending north and south, from a little north-east of Leeds, nearly to Derby, a distance of above sixty-five miles; its greatest width is on the north, about twenty-three miles; whilst it reaches nearly to Halifax on the west, and to Nottingham on the east. Midland Railway traverses this coal field, and has consequently caused a great increase in the working of the collieries. The towns of Leeds, Halifax, Bradford, Huddersfield, Wakefield, Chesterfield, Sheffield, Nottingham, Pontefract, and Derby, are situated upon, or adjoining to, this coal district, which supplies fuel to the important manufactures carried on in the neighbourhood; and, by means of the railways, to the counties lying south-east of Derbyshire. The number of coal seams contained in it has been estimated at upwards of thirty, varying from six inches to eleven feet, and constituting a total thickness of twenty-six yards, with numerous alternations of grit and argillaceous strata, some of them containing ironstone. The various workable beds of coal known to exist in the South Yorkshire coal field are the following:

The total being fourteen beds, comprising an aggregate of fiftyone feet, three inches in thickness. The most important of these seams are the "Silkstone" and the "Barnsley," or "Thick bed," which, taken together, have an average thickness of twelve feet.* The thickness of the entire coal series in Yorkshire exceeds 8,000 feet.

There are also detached coal fields in the north of Yorkshire, but they are comparatively limited; lying generally in the hollows of the grit-stones.

3.-The Coal field of North Stafford.

This is sometimes called the "Pottery Coal Field;"it is a small detached district, whose greatest breadth is about fifteen miles; having Cheadle and Newcastle-under-Lyme on its eastern and southern extremities, and Congleton on its north-western edge.

It has been ascertained to contain about thirty-two beds of coal, from three to ten feet thick, which are found at various depths from fifty to four hundred yards. The strata are subject to great dislocations, and dip from the sides towards the centre of the basin, with an inclination on the eastern side of one in four; while on the western side it is still more steep. Some seams, only twenty inches in thickness, have been worked; but they are generally neglected if they are of less thickness than four feet.f There are some very extensive iron-works situated upon this coal field.

4.--Manchester, or South Lancashire.

This coal field is an irregular, crescent-shaped tract, the span of which is about forty miles. It extends from the borders of

*Trans. South York Viewers' Association.-Vol. I.

†Trimmer's" Geology."