466 



Sir Roderick Murchison has argued that, inasmuch as the 

 Somersetshire coal field is apparently entirely cut off to the east- 

 ward by older rocks ranging from Wickwar through Bath to 

 Frome, and as the French coal field is cut off to the westward by 

 Devonian rocks, which have been met with immediately below the 

 chalk, there is no reason to expect Coal measures in the intervening 

 area. He has argued further that the continental coal fields 

 become deteriorated in proceeding westwards, so that even if coal 

 strata should exist in the south of England, they would probably 

 be of no commercial value. 



While the alleged deterioration is disputed by some authorities 

 the other statements cannot be denied, but the argument Sir 

 Roderick based on these is not conclusive. Subordinate to the 

 principal east and west axis there would appear to have been many 

 cross lines of disturbance which have separated the South Wales 

 coal field from the Forest of Dean, the Forest of Dean from 

 Somersetshire, and which have in like manner split up the conti- 

 nental coal field into many parts. The Devonian rocks of the west 

 of France and the Mountain limestone to the east of Somersetshire 

 may therefore be only additional examples of these transverse 

 elevations of the older rocks, and their presence at opposite ends of 

 the area under consideration by no means implies the absence of 

 Coal jn-eofSMres between. 



The only other evidences of palaeozoic rocks bearing on the 

 question are the presence of Cambrian rocks at Chamwood Forest, 

 and the fact that at Harwich the Carboniferous limestone and near 

 London the Devonian have been found to underlie the chalk, but 

 these lie to the north of the supposed basin of productive Coal 

 measures, and we must hope that the Wealden boring will shortly 

 throw additional light on the subject. 



Another possible coal area, which has given rise to a good deal 

 of discussion, lies to the south of the great axis of disturbance to 

 which I have referred, in the country intervening between the 

 Mendips and the Quantock hills, and under the Bristol Channel to 

 the south of the Welsh coal field. The Mendip range, as I have 

 already said, is a true anticlinal, the centre of the ridge being 

 occupied by the Old red sandstone, from which the Mmintain lime- 



