CARBONIFEROUS LIMESTONE OF SOUTH WALES, ETC. 



155 



New Red Sandstone than any hitherto penetrated ; for as it appears that the most 

 important seams on the west, dipped to the east and south-east, so is it possible that 

 the measures may be found to have expanded, when followed upon their dip. Whether 

 this prove to be the case or not, there can be little doubt that these carboniferous 

 strata, in some form or other, are prolonged beneath the New Red Sandstone to the east 

 of Newent, as indicated by a highly sulphureous medicinal spring, which there rises to 

 the surface 1 ; whilst there is every probability that the strata being further removed from 

 their junction with the Old Red Sandstone, may run in more continuous and unbroken 

 masses, than in those spots along the line of outcrop, to which all previous undertakings 

 have been confined. 



West. 



17. 



a. New Red Sandstone. b. Coal Measures. c. Old Red Sandstone. 



The importance of the discovery of a really productive coal-field in this accessible and 

 level tract, is too obvious to require notice, seeing its contiguity to that part of Gloucester- 

 shire on the one side, where the overlying formations are of great thickness ; and to 

 those wide agricultural tracts of Herefordshire and South Worcestershire on the other, 

 in which, from their geological relations, no coal can ever be detected. 



1 By this observation, I do not mean to imply that sulphureous waters are always to be taken as proofs of 

 the existence of carboniferous strata. (See remarks on Mineral Waters, p. 34.) Here, however, the reason- 

 ing would be as follows. The coal measures which crop out on the west, contain much iron pyrites, which on 

 decomposing would afford sulphureous springs ; on their dip to the east, these beds pass beneath a cover of 

 New Red Sandstone, in which no pyrites is observed, and hence it is fair to infer, that the waters which have 

 flowed upon the inclined and pyritous beds of the coal measures, after becoming highly sulphureous, rise to their 

 original level through cracks in the overlying sandstone. In fact the depression in which the spring rises, is 

 probably the scene of a fault, by which the coal measures are thrown up to the east of this mineral source. 

 (See Wood-cut above.) 



Northern, Western, and Eastern edges of the great Coal-basin of South Wales. 



Carboniferous Limestone. 



The value of its mineral contents, and the great extension of the South Welsh coal- 

 basin, entitle it to be treated of in a separate work, and geologists may well rejoice that 

 the task of describing it has been undertaken by the Rev. W. Conybeare. I have, 

 therefore, not attempted to examine in detail any part of this basin, but have confined 

 my observations to that portion of its margin which is conterminous with those ancient 



