the seams at the eastern side of the Lancashire and Cheshire coal-field are thin, and much split up by partings of shale.

The Royley or Arley Mine, at the base of the middle coal-series, has been extensively worked around Oldham, and as far south as Lees, but has never been proved at Ashton-under-Lyne. Further south, it is considered, with great probability, to be represented by the Upper Woodley Mine, which has been worked in Cheshire, and upon this supposition we have been enabled to trace this remarkable coal-seam over the entire coal-field, with an area of nearly 200 square miles. It is considered, also, to reach into Yorkshire and Derbyshire, where it is called the Black Shale or Clod-coal.

The Black Mine forms the most valuable seam of this district : Oldham and Ashton are built upon it, and, consequently, the interior of the earth is perfectly honeycombed under these densely-populated towns. Under Oldham, indeed, little of this seam remains entire, and the workings have advanced towards the west and south, where a large area still remains, most of which is in the hands of the Chamber Colliery Company. It is this seam to which the Astley Pit of Dukinfield Colliery has been sunk, at a depth of 687 yards, the greatest yet attained by one vertical descent in Britain, if not in the world. The workings in this magnificent colliery extend, however, to a considerably greater depth even than this. The dip of the Black Mine being rapid, and the seam having been followed by a "down-brow" tunnel, a depth of, we believe, 2,500 feet from the surface has already been reached; and should it be found practicable to drive in the same direction to the extremity of the estate, a total depth of about 3,300 feet or more will ultimately be attained. We look forward with extreme interest to the progress of the workings of this remarkable colliery. Much light may be thrown on the effects of the weight of the superincumbent strata, the pressure of the atmosphere, the powers of ventilation, and of the increase of temperature at great depths. Already two of these influences, namely, the thrust of the strata, and increase of temperature, are making themselves very sensibly felt; but we feel sure that, under the skilful management of Mr. Charlton and his intelligent underlooker, these obstacles to the extraction of the coal will (as far as is possible) be surmounted.

The Black Mine varies in thickness from 4 to 5 feet, and at a short distance below it is a seam which yields a good cannel, about 18 inches thick at Dukinfield.

The uppermost workable seams are the Great Mine and Roger, both thick and moderately good coals; but owing to the small extent of surface which they occupy, they have not as yet been largely worked.

After crossing into Cheshire, the coal-field begins to contract in breadth, and ultimately ends off in a point in the direction of Macclesfield. This is owing to the existence of a large fault, which throws in the New Red Sandstone on the west against the Coal-measures which gradually rise and crop out southwards until ultimately the millstone grit reaches the surface. The vertical displacement of this fault must be several thousand feet, if not yards.

Having concluded our short account of the principal coal-seams, it may not be altogether useless or uninteresting to point out some of the districts where the coal lies for the most part undisturbed, and to

FIG. 2.

which we may look for the future supply, when the mineral shall have been more or less exhausted in those localities where it is at present most largely mined. We shall presently offer some details, showing that the exhaustion is proceeding with accelerated speed, and it therefore becomes a question of importance, whether there are still remaining certain tracts as yet unopened up, where the coal may be found at a future day within workable depths.

We are glad to be able to state that as far as the Lancashire coalfield is concerned, there are several districts of considerable extent, where some of the most valuable seams lie in all their primeval integrity, at depths within a thousand yards, and therefore certainly available. That which is best known and appreciated is the belt of country lying to the north of the Mersey, and forming the southern limit of the coal-field. Although formed of New Red Sandstone and Permian strata, it is well known that the coal-seams dip under these newer formations, and have in several collieries actually been worked underneath. Of these we may mention the collieries of Haydock, Edge Green, Astley, Bedford, and Patricroft. It will, however, in all probability, be a long period before the New Red Sandstone is extensively invaded by coal-pits.

One of the most important districts for future supply is that which lies to the south and south-east of St. Helen's, and extends as far as the Railway Junction in the direction of the dip of the beds. At this deepest point the vertical distance to the St. Helen's Main Coal would be a little over 1,000 yards; and at every step nearer St. Helen's the depth would be lessened.

In the Wigan district, besides the "deep belts," in which the Arley Mine lies at a depth of 1,000 yards and upwards, with several shallower seams of great value, at still smaller depths, there is, also, the tract lying between Standish and Coppul, which has been very little explored, and which contains three or four seams of workable coal. There is a considerable tract of virgin ground formed of upper coalmeasures around Abram, and extending as far east as the great fault west of Bickershaw Colliery. Here several seams would be found at depths under 1,000 yards. Between Bickershaw Higher Hall and West Leigh Hall, there is another tract of upwards of a square mile in extent, where the coal lies as yet undisturbed. This band of coalmeasures extends as far west as the large fault just referred to, which introduces the New Red Sandstone.

Perhaps the most important band of country for future coal supply is that which stretches on either side of the outcrop of the Worsley 4-feet seam, from the great fault which runs within half a mile to the N.E. of Leigh and Bedford to Monton, a distance from west to east of six miles. Over every portion of this tract, on the north side of the outcrop of the Worsley 4-feet Mine, all the seams, including the Arley Mine, may be reached at depths within 1,000 yards. South of this outcrop none of the underlying coal-seams have as yet been touched; and there is, therefore, an area of about 10 square miles, in which the 4-feet coal lies at a depth considerably under 700 yards, and several deeper seams, such as the Rams Mine, under 1,000 yards. Many of these seams may be worked (as already hinted) under the New Red Sandstone, which runs for the most part parallel to the trend or "levels" of the coal-seams in this district.

FIG. 3.

GENERAL SECTION, SHEWING THE SUCCESSION OF THE COAL SERIES WEST OF MANCHESTER.

Proceeding eastward, the next district of reserve of special importance is that which lies along the northern outcrop or border of the New Red Sandstone and Permian strata from Ringley to Prestwich, and some distance further eastward. This tract is much obscured by sand and clay, so that the strata are rarely visible even in deep brook Still, judging from the southerly dip of the coal-seams which reach the surface along the banks of the Irwell, as far east as Radcliffe Bridge, there can be little doubt that this district is full of coal. The construction of shafts will, probably, be attended with much difficulty and expense, owing to the depth of the running sand.

courses.

The Manchester coal-field ought, according to all the recognized principles of stratigraphical succession, to contain a vast supply

of coal below the seams now being worked; but from some unexplained cause these have never been reached in the trial-borings which have been made.

To the north and east of the margin of the New Red Sandstone, from Middleton to Denton, there runs a band of about ten square miles, stored with all the coal-seams of Oldham, Ashton and Dukinfield, but at greater depths as being further removed from the outcrop. On this tract is situated Mostyn Colliery, at which the upper Great Mine is worked at a less depth than 300 yards; consequently the Black Mine would be found at less than 1,000 yards at this spot, and throughout the greater part of this band of coalmeasures the dip is likely to be found rather steep, and the ground considerably broken by faults.

There are, therefore, from 30 to 35 square miles of what may be considered as reserve-ground, plentifully stored with coal at depths varying from 2,000 to 4,000 feet, which is as yet scarcely broached.

FAULTS OR DISLOCATIONS.

The Lancashire coal-field is remarkable for the magnitude of the lines of fracture by which it is traversed, and in some parts bounded. The western boundary of the coal-field is a large fault, which throws in the New Red Sandstone along a line ranging from Lathom Park on the north, by Bickerstaffe and Knowsley Hall to Huyton and Tarbock. The throw of this fault may probably reach 1,000 yards

in some places.

The "Great Up-Holland" fault, which ranges north and south by Pimbo Lane, has a throw of 700 yards. The effect of this dislocation is to reintroduce a large area of coal-ground to the west of its outcrop at Billinge, Orrell and Up-Holland. On this area-which is the nearest collieries to Southport and the northern suburbs of Liverpool-are situated the collieries of Rainford, Blaguegate, Swifts' Folds, Skelmersdale and Holland.

Of the five great parallel faults which traverse the Wigan district, the "Pemberton Fault has a throw of 470 yards at Tan House Colliery; the "Shevington Fault" of 600 yards opposite the John Pit of the Kirkless Hall Company; the "Giant's Hall Fault" of 600 yards, west of Ince Hall Colliery; the "Standish Fault" of 160 yards at Amberswood Colliery; and the "Great Haigh Fault" of 600 yards near Kirkless Hall Colliery. In general, notwithstanding the magnitude of the vertical displacement occasioned by these great fractures, they are remarkably "clean," very little broken or barren ground being found on either side of them. They have proved of immense benefit to the mining operations of the district, as they form natural barriers for damming the waters in old workings. On this account great precautions are taken by colliery owners on both sides, that the natural sluices may not be cut through.

The Worsley district is traversed by three parallel faults varying east and west in the same direction as the outcrop of the coalseams. The most southerly of these may be traced over five miles; the others for a less distance. The effect of these faults is to repeat several of the same seams twice, or thrice; so that in traversing the district from south to north (in the direction of the dip and rise) we