SILURIAN ROCKS BENEATH THE COAL. 



489 



concretions of impure limestone. It is difficult to determine the exact relations of this band to the 

 thicker strata of Wallsall, from which it is separated by an argillaceous tract of more than a mile 

 in width; for whilst, from its dip to the north- west, we might be disposed to consider it an inferior 

 stratum, the organic remains on the whole are the same as those of the limestone hills of Dudley. 

 There are also evidences of this mass being bent over in a saddle shape, dipping both to the south- 

 east and north-west (See PI. 37. f. 3.), while there is reason to think, that a thin course of un- 

 productive coal measures is interpolated between it and the New Red Sandstone of the Bar Beacon. 

 In addition to some of the usual and well-known fossils, the band of Hay Head contains a good 

 many large orthoceratites, and the rare trilobite of the genus [sotelus ? (commonly known in this 

 part of England as the Bar trilobite, from the hill of the Bar Beacon lying immediately to the east 

 of the lime works where it is found). The banks of an abandoned canal between Hay Head and 

 Daw End exhibit a great variety of the smaller shells and corals so characteristic of the Wenlock 

 shale. (See Plates and Descriptions.) 



Silurian Rocks, including Limestone beneath the Coal-field. 



Having shown that the upper Silurian rocks, either rising in isolated masses, or 

 forming the edge of the coal-field, dip in all cases under it, it would naturally be ex- 

 pected that the limestone would have been sought for beneath the coal. These relations 

 being surmised, have been partially ascertained in the Wolverhampton district, where 

 the coal measures being thinner are more easily penetrated. 



Mr. J . Barker, for example, informed me that in one of his collieries, sinkings and borings were 

 carried down 150 yards beneath the "blue flats/' or bottom of the Wolverhampton field; and that 

 at a depth of eighty yards, the works passed through a sort of limestone clunch, which continued 

 with occasional small beds of limestone to the end of their operations. I have little doubt that 

 these works traversed the parts of the Ludlow formation, and that the Wenlock limestone would 

 have been found beneath. Again, at the Park Field colliery, one and a half mile east of Wolver- 

 hampton, beds of limestone abounding in shells and corals, were formerly found beneath coal mea- 

 sures and grit. This rock was evidently the black limestone of Sedgeley, which rises up to the 

 surface half a mile south of this colliery. (See Map.) 



In the centre, however, of the deeper or ten yard coal-field, the lower coals being 

 seldom penetrated, these rocks had not been reached till very lately, and few or none 

 of the practical men were of opinion that the same limestone which formed the side of 

 their field could exist beneath it, when one of those happy accidents occurred, by which 

 miners are enriched (may we say it) in spite of themselves, and geologists are gratified 

 in the display of facts, confirmatory of views founded upon a general knowledge of the 

 structure of the country. Having exhausted the coal in certain works at Dudley Port, 

 the proprietors, in the hope of finding coal and ironstone, were induced to sink a fresh 

 trial shaft upon the side of, or rather in, the great fault which bounds upon the S.E., the 

 trough of coal before described. (See PL 37. f. 1.) At a depth of 208 yards, and about 

 100 yards beneath the old coal works on the south-east, they came unexpectedly upon 



