Vol. 63.] BASEMEjSTT-BEDS OF THE BRISTOL COALFIELD. 447 



The Ashton-Vale Colliery, in which the section about to be 

 described was obtained, lies on the south-west side of Bristol. The 

 surface-deposits consist of river-alluvium, underlain by the New Red 

 Sandstone and New Red Conglomerate, which in turn rest upon 

 the upturned edges of the Coal-Measures. To the north, however, in 

 Ashton Park, members of the Millstone Grit crop out in several 

 places, and the Carboniferous Limestone comes to the surface over 

 a large area. Owing to the overlap of the Trias, the junction of the 

 Millstone Grit and the Coal-Measures is nowhere seen at the 

 surface, and the precise limits of the two have thus been a matter 

 of conjecture. 



A generalized statement of the pit-shaft section at Ashton-Vale 

 Colliery is as follows : — 



Thickness in feet inches. 



Clayey alluvium 22 



New Red Sandstone and Conglomerate 64 6 



Coal-Measures : — 



Strata 126 3 



Coal 2 



Strata 45 6 



Coal 4 



Strata 82 9 



Coal (Red Ash), ? Little Toad Vein 2 9 



Strata 39 6 



Coal 3 3 



Fireclay 4 



Coal 1 



Strata 39 



Coal 1 



Strata 157 6 



Coal (Top Vein) 4 



Strata 43 3 



Coal (Great Vein) 4 6 



Strata 122 



Coal (Red Ash), ' Little Vein * 2 



770 9 



The dip appears to have been fairly regular throughout, and to 

 the south at the rate of 1 in 3. Since the formation of the shaft 

 all the seams have been mined to the deep to a considerable 

 depth. 



The exploration- branch commenced at the level of the ' Red Ash ' 

 or ' Little Vein ' of Ashton Yale, and was carried horizontally in a 

 northerly direction, cutting the underlying beds successively as they 

 rise to the edge of the basin. The rate of dip kept fairly uniform 

 with that in the shaft ; and, when a thickness of about 820 feet of 

 thin coals, shales, and mudstones had been penetrated, the branch 

 passed into beds of gritstone 70 feet thick which yielded water. 

 From this point onwards, grit-rocks predominated ; and, after a 

 distance of about 450 yards had been penetrated, the work ceased 

 in a massive fine-grained grit with mudstone-partings, from which 

 the water burst in and flooded the level. 



The result of the exploration has been to show that the ' Gays 

 Q. J. G. S. No. 252. 2 k 



