As we approach the alpine district on the west side of England, rocks of a similar class to those in Wales are met with, but surrounded by the secondary strata of the middle district : the most considerable of these are the Malvern hills, and the Caradoc hills in Shropshire. Ac cording to Mr Horner, the central parts of the former are principally composed of granitic rock, mixed with horneblende : the lower declivities are covered with lime stone and sandstone. The Caradoc and Wrekin hills are composed of a variety of green stone ; some of them con tain actynolite : on the sides of these hills are singular beds of claystone, containing cells, flattened as if by pressure since their formation.
The mountains, on the eastern side of North Wales, are composed of limestone, containing lead and zinc. The limestone is similar to that of the northern range : detached coal fields are met with on their lower declivi ties, in Flintshire and Denbighshire. The limestone rests on slate, which, as we proceed to the west, is seen rising from under it : in the same direction, mountains, princi pally composed of grey wacke, flinty slate, and roof slate, are found : veins of quartz, containing copper ore, also occur. Organic remains have been discovered in the slate of North Wales ; it has not been ascertained that any true granite has been found here : in Anglesey there is serpentine, however, which, from its hardness, beauty, and tendency to a crystalline arrangement, may perhaps be regarded as a primary rock. Diallage, intermixed with steatite, is found in two mountains, on the eastern side of Radnorshire. Rocks composed of cellular clay stone, resembling lava, are met with to the west of these mountains, at Llandegley. The north side of Cader Idris, is covered with scattered basaltic columns, corn posed of porphyritic greenstone : this mountain contains silicious porphyry in mass, intersected by veins of quartz ; silicious schistose porphyry, also intersected by veins of quartz ; argillaceous porphyry in mass ; and granite com posed of quartz and schorl in mass.
It has already been mentioned, that limestone is the foundation rock of the great coal formation in South Wales. The principal mineral treasures of the alpine districts of Wales, are copper, lead, and slate ; and of the less elevated districts, coals and iron stone.
We shall now pass to the Devonian range of the al pine district. The strata of the middle district rise at an elevated angle, as they approach the granite rocks of this range. The western boundary of the coal dis trict in Sontersetshire is formed of metalliferous lime stone and grey wacke, which pass from that county into Devonshire and Cornwall. Mountains of granite
extend from Dartmoor to the Land's End. Slate, grey wacke, and sometimes metalliferous limestone, occur on their declivities and summits. At the Lizard, the granite rocks are covered with serpentine, near which diallage in rocks is found. In the serpentine also, soft steatite is imbedded. The most extensive and valuable mineral treasures of this part of the alpine district are copper and tin ; besides these, ores of silver, cobalt, bis muth, manganese, antimony, zinc, and iron are found. Indeed, it has been remarked, that all the 27 known metals are met with in Cornwall, except platina, mer cury, molybdena, tellurium, tantalium, columbium, and cerium. In some of the granite rocks of Cornwall, schorl is found intermixed ; and in some particular places, it constitutes the principal part of the rock.
Having given this general sketch of the mineral geo graphy and geology of England and Wales, arranged into districts, we shall now proceed, in order more fully to illustrate this important subject, to offer some mis cellaneous remarks, though at the risk of repeating some of the statements which have been already made.
To begin with the primary rocks. Granite and gra nitic rocks occur in Cornwall, Devonshire, North Wales, Anglesea, the Malvern Hills in Worcestershire, Chant wood Forest in Leicestershire, and in Cumberland and Westmoreland. The granite of these two counties is, however, porphyritic ; and that of Charnwood nearly allied to sienite. Blocks of granite are found detached in some parts of Lancashire and Cheshire. Glick is found no where in England, except at the Malvern Hills; and here it is imperfectly formed. Mica slate occurs only in Cornwall, where, along with it, lying over gra nite, serpentine, another primary rock, is also found exclusively, with the exception of the Isle of Anglesea.
Of the intermediate or transition rocks, slate is found in Westmoreland, Yorkshire, Leicestershire, North Wales, Cornwall, and Devonshire. In the Yorkshire slate are cubic crystals of pyrites. In the slate rock at Charnwood Forest, in Leicestershire, the slaty la minx make an angle of 60 degrees with the principal seam, by which the rock is divided. Graywacke is met with in Cornwall, where it is called killas. In the northern part of Radnorshire is a lofty range of moun tains, composed of graywacke, which, on the eastern side, resembles sandstone, and on the western, roof slate.