260 Messrs. Buckland's and Conybeare's Observations on the 



In the coal-basin of Nailsea the Pennant covers an area 1^ mile broad on 

 Nailsea heath, and the upper seams of coal worked in that field appear to be sub- 

 ordinate to this rock. In the Clapton coal-field the Pennant along the line of 

 fault abuts, as has been already stated, against the mountain limestone. The 

 occurrence of this rock on the coast at Portishead has also been noticed. 



4. The upper coal-shale consists principally of slaty clay, alternating with 

 some thin beds of grit, called greys, a word, perhaps, of the same origin with 

 the French grhs. Impressions of ferns are very abundant in this shale, and 

 some Lepidodendra occur. [See Sternberg's Flora zur Vorwelt.~] Some of 

 the collieries worked in the upper shale, those of Radstock for instance, are 

 subject to the fire-damp, which is hardly known in those of the lower shale, at 

 Bedminster or in the southern coal-tract. 



The diameter of the upper shale, within the zone of Pennant, in the trough 

 of Coal-pit heath, is rather more than 2 miles. The strata dip regularly 

 towards the centre of the trough about 1 in 6 on an average. Three seams of 

 coal are worked, the hard vein, the hollybush, and the great vein, containing 

 in the aggregate from II to 12 feet of that mineral. (See 18th Coal-section.) 

 They all consist of excellent slaty caking-coal, free from bad smell in burning. 

 The hard vein, however, is sometimes stony, containing black ponderous no- 

 dules, and is of a less regular structure than the other seams. No shells have 

 been found in the strata at Coal-pit heath. Vegetable impressions occur chiefly 

 in the roof of the seams, immediately above the coal. The pits are free from 

 fire-damp. The coal-measures in Coal-pit heath are traversed by several faults. 

 One commences at Mays-hill, crosses the turnpike-road at Oxbridge, and runs 

 about 1 mile to the south. That near the Engine-pit at Bitterwell is supposed 

 to be a continuation of this fault. Another occurs to the east of the Serridge 

 engine, running westwards under the engine towards Kendleshire. A third 

 fault is found about 1 100 yards to the south of the Serridge engine, behind 

 Wait's farm-house at Henfield, and thence runs east towards Lyde Green. 



In the trough of Radford the upper coal-shale constitutes a very irregular 

 area, whose longest diameter, from Brislington on the N.W. to Kilmersdon on 

 the S.E., is about 12 miles, and whose shortest diameter from N.E. to S.W. 

 is about 5 miles. Its western border follows an indented line from Brisling- 

 ton to Burnet, Pensford, Stanton Drew, Bishops Sutton, Clutton, Faringdon- 

 Gurney, and Midsummer Norton. Thus far it can be traced by the range 

 of coal-seams, which are known to be nearly contiguous to the Pennant; 

 at the other sides of the trough its boundaries are concealed by the overlying 

 rocks. 



The first part of the western border near to Brislington presents a seam of^ 



