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 GEOLOGY Jukes, the unconformity was distinct, although the discordance was not very striking. Of especial importance in the region is the Fire-clay, mined at King's Swinford and Old Swinford, near Stourbridge, for the manufacture of fire-bricks, saggers, crucibles, etc. Fire-clay is one of the kinds of impure clay in the Coal Measures, and is usually regarded as an ancient exhausted soil. The clay, in consequence, will bear intense heat without melting, because of the small amount of lime, protoxide of iron and alkalies contained in it.^ Many plant-remains have been obtained in the South Staffordshire coalfield from the shaly beds, notably giant club-mosses {Lepidodendron and Sigillaria), horse-tails {Calamites), and sundry ferns. Freshwater or estuarine mollusca such as Anthracosia also occur ; and there are marine fossils, such as Aviculopecten, Lingula, etc., as well as fishes, such as Megalichthys, which have been found in some of the ironstone bands belonging to the Lower Coal Measures. PERMIAN Throughout the greater part of the country there is a marked break between the Coal Measures and the succeeding deposits of Red rocks, the lowest portion of which is grouped as Permian. This unconformity is conspicuous along the eastern side of the exposed coal-fields of Derby- shire, Yorkshire and Durham. In the Dudley district we find that the so-called Permian rocks are nowhere distinctly unconformable to the Coal Measures, and at one time they generally overspread the area. The Permian is divided into : — Feet. Upper Sandstones and marls (local) ..... 300 Breccia, sandstones and marls, with beds of calcareous conglomerate | 200 to 500 Lower Sandstones and marls 500 to 850 The mass of the Lower Sandstones and marls and some higher beds have in recent years been proved to contain not only occasional layers of limestone with Spirorbis, but also thin coal-seams. They evidently con- stitute a portion of the Upper Coal Measures. Mr. T. C. Cantrill indeed is inclined to regard the whole series up to the Upper Sandstones and marls, a series which may be 1,500 feet thick, as belonging to the Upper Coal Measures.^ The breccia of the Clent Hills, which is reckoned to be about 450 feet thick, forms a bold range of hills rising to a height of 1,028 feet. The breccia is overlaid by the Bunter pebble-beds and the range extends by Romsley to Bromsgrove Lickey, which is about 900 feet high. At Northfield the strata are well exposed. 2 Quart. Journ. Geol. Soc, vol. li. pp. 530-533, and Coll. Guard., vol. Ixxiii. (1897) p. 581 ; see also W. W. King, Quart. Journ. Geol. Soc., vol. Iv. p. 97. 13
 * See Analysis in Percy's Metallurgy, vol. i. p. 98.