The middle district of England, in a mineralogical and geological point of view, which is bounded on the cast by the calcareous range that extends from Dorset shire to Yorkshire ; and oo the west from Northumber land to Derbyshire, by the metalliferous limestone moun tains of the northern alpine district, or by mountains of millstone grit, resting upon limestone, consists of argilla ceous and silicious sandstone. The secondary strata of this district extend west, till they touch the Irish sea, on the coast of Lancashire ; or, farther south, are bounded by the alpine districts of Wales and Devonshire. The strata here arc very irregular, hills of transition and basaltic rocks rising through them, and branches from the mountains of Wales, shooting, as it were, into this district, especially in Shropshire, and in a line extend ing from that county to the hills of Charnwood forest in Leicestershire. Basalt, or whinstone, also appears in this district, in the eastern moorlands of Yorkshire, which forms the highest part of it : the sides of the hills com posing these moorlands, are covered with a bed of altiniinous schistus, upwards or 100 yards in thickness ; this schistus forms cliffs, extending in a waving line along the coast near \Vhitby : above it lie vegetable soils of various thickness: loose stone or rubble of un certain thickness : coal from four to eight inches thick : compact iron stone, 24 inches thick, and broken iron stone five inches thick.
The princip .1 cot fields, in the northern part of this district, lie in Northumberland and Durham, the west riding of Yorkshire, and Derbyshire: the strata of coal terminate a few miles to the north-east of the town of Derby, but make their appearance again to the south of the Trent in Leicestershire, near Ashbey de la Zouch : on the south-east, they terminate at the Charnwood while, on the south-west, a thick bed of coarse breccia and gravel, separate them from the coal fields in the county of Warwick. A considerable part of the western side of the middle district, from the southern division of Lancashire to Somersetshire, is occupied by a red sand rock ; which extends through part of the counties of Lancashire, Cheshire, Staffordshire, Shropshire, and \Vorcestershire : the southern extremity of this rock, in Shropshire, rests on highly elevated strata of grey wacke ; and it is probable that it rests, through its whole extent, on transition rocks. No coal is found un der the sand rock, and it seems to cut off the coal fields, which lie near, or upon it : it occurs at a very low com parative elevation. The principal salt springs, and the rock salt of Cheshire, are near, or on the red sand rock, in the vicinity of a range of lofty hills, which extend from the high peak in Derbyshire to Browngrove Lickey in \Vorcestershire. Near Northwich, in Cheshire, the upper bed of rock salt lies 42 yards below the surface, and is 26 yards thick : it is separated from the lower bed by a stratum of argillaceous stone 10 yards thick ; the lower bed has been penetrated to the depth of 40 yards ; its breadth is 1400 yards, and, in one direction, it has been ascertained to extend 11 mile. Three other beds of rock-salt have been found in another part of the county : the uppermost four feet ; the second 12 feet thick ; the third has been sunk into 25 yards. Brine springs are likewise met with at Droitwich in Wor cestershire, in the midst of a similar red sand-stone. The strata here are as follow : from the surface mould, five feet ; marle, 35 feet ; gypsum, 40 feet ; then a river of brine 22 inches ; afterwards gypsum again : and be low this, a rock of salt, into which the workmen have bored five feet.
Although, as we have already remarked, the red sand stone rock cuts off the coal fields in general, yet in some parts of Lancashire and the western counties, detached coal fields arc surrounded by it. The greatest quanti
ties of coal, however, in this district, are in Stafford shire, and that part of South Wales that borders on the Bristol Channel : all the strata of coal and iron stone in South \Vales, are deposited in a limestone basin, the form of which is an it regular oval ; in length 100 miles, and where broadest from IS to 20; its greatest breadth is in the counties of Nlonmouth, Glamorgan, Caermar then, and Brecon : in Pembrokeshire it is not more than five miles broad. The deepest line in this basin is be tween Neath in Glamorganshire, and Llanelly in Caer marthenshire : the uppermost stratum of coal is found here : the utmost depth of this stratum does not exceed 50 or 60 fathoms. The succeeding strata of coal lie deeper, and are accompanied with parallel strata of iron ore : the lowest strata at the centre range are from 600 to 700 fathoms deep. In this basin there are 12 strata of coal, from three to nine feet thick, and eleven others from 18 inches to three feet, making in all 95 feet. The limestone that forms the substratum of this mineral de position, appears to the surface all along the boundary of the basin, and is supposed to have an underground con nection from point to point.
As we approach the south-western counties, the mid dle distiict becomes very narrow, the calcareous strata of the low district approaching near the primary and transition rocks.
The alpine district of England and Wales is formed by an assemblage of lofty mountains, which pass along the western side of the island : the eastern side of the northern range of these mountains, from Cumberland to Derbyshire, is composed of subcrystalline metalliferous limestone, which in many parts is covered with the mill stone grit, and shale grit, that have been already des cribed. In the south-west part of Yorkshire, the lime stone, for more than 20 miles, is covered by the incum bent grits ; the mountains of Craven again exhibit it ; and it rests on slate in Swaledale, at the base of Ingle borough, and in other parts adjoining Westmoreland. The mountains of this county and Cumberland are com posed principally of grey wacke, flinty slate, roof stone, and porphyry : a low range of granite rock rises near Snap in Westmoreland, and marble is found in different parts of this county. In this part of the northern range, ores of lead, copper, and zinc, are found: in some parts of Craven, carbonate of lead and galena are raised. The north-west of Lancashire, which composes that district called Furness, consists for the most part of coarse slate and grey wacke : red hematite, a very rich and valuable iron ore, is procured in great abundance in this part of the country, particularly between Ulverstone and Fur ness Abbey. The southern part of this range consists of the rocks of Derbyshire : these consist of limestone and basaltic amygdaloid : it is supposed that the former rest on slate : there are here three beds of limestone, the depth of which and the basaltic amygdaloid, is up wards of 250 yards ; in some parts a fourth bed of lime stone is found, thicker than any of the others. The total depth of all the known Derbyshire strata, includ ing the small portion of Nottinghamshire, which con tain the magnesian limestone, is 1310 yards. In this range there are 30 beds of coal, varying in thickness from six inches to 11 feet : the total thickness of coal is 26 yards. Hence it appears, that as the thickness of the strata of the low district, (as has been already ob served,) is about 700 yards, we must sink 1300 yards deeper, to arrive at the limestone incumbent on slate rocks, the depth of which, below the stratum of clay, in the valley of the Thames, must consequently be about a mile and a quarter.