South-western Coal District of England. 253 



The millstone-grit may be seen at the following places^ either in the Kings- 

 wood ridge or along the borders of the coal-basin. In the northern coal-tract 

 at Cromehall it reposes on alternating beds of grit and limestone, dipping south- 

 wards at an angle of 35° ; and hence it stretches towards Titherington, though 

 concealed at the latter place by overlying beds of lias. Still further to the 

 south it is found resting against mountain limestone in Knoll-park near Al- 

 mondsbury. Between Sodbury and Yate it may be seen on the road-side. On 

 the borders of the eastern and western coal-tracts its position has already been 

 described ; on those of the southern it every where intervenes between the 

 other coal-measures and the limestone, lying parallel to the latter, and being 

 nearly vertical. It here frequently contains beds of the most decided conglo- 

 merate. It appears also as a quartzose conglomerate between the coal and 

 limestone along the northern frontier of the small coal-basin of Nailsea, and 

 may be traced over Nailsea-heath, a long- slip of swampy ground lying- north 

 of the village. It is the lowest of the beds exhibited in the saddle of Kings- 

 wood, and may be studied in the quarries on the north side of the new church 

 of Kingswood, where it dips rapidly to the north. An axis of this rock pro- 

 bably exists near the surface along the whole diameter of the elevated plain of 

 Kingswood. The saddle is said by the most intelligent miners to abound with 

 contortions and undulations. 



2. The Lower coal-shale, which reposes on the millstone -grit, consists prin- 

 cipally of argillaceous strata, even the grit, which alternates with the shale, 

 containing much clay, and occasionally resembling some of the varieties of 

 grey-wacke. Slate-clay predominates, and imparts its character to the whole 

 series. This, when very fissile, is called by the miners, on account of its easy 

 cleavage, " cliff" or " dives ;" but when compact, and less disposed to cleave, 

 it is called " duns," a word obviously of the same origin as the German 

 "thon." Ironstone occurs in some of the lower beds of shale. Vegetable 

 remains, particularly those of long-fluted reeds, and of trunks marked on 

 their exterior by lozenge-shaped impressions, are common ; but those of ferns 

 are less so than in the upper coal-shale. 



The coal-seams are improperly called veins by the miners throughout the 

 Bristol coal-basin. Many seams belong to this lower series ; but no permanent 

 distinctions have been ascertained between those of the upper and lower coal- 

 shale ; and it is only by their position in relation to the Pennant coal-grit that 

 we are able to distinguish them. 



In the northern part of the northern coal-tract two sets of coal-seams have 

 been ascertained to exist between the millstone and Pennant grits ; those of 

 Cromehall, which contain three seams, and those of Yate, which contain four. 



