82 SECTIONAL ADDRESSES. 



north-westerly direction for several miles, then resumes its westerly course 

 until it crosses to the north side of the Vale of Pewsey. It appears to 

 have been determined locally by the position of the most important fold 

 which traverses the chalk outcrop, and as this tends to occur farther north 

 in the west than in the east, so the watershed migrates in that direction. 



If, however, we follow from the Vale of Pewsey the water-parting 

 between the streams that flow into the Bristol Channel and those that flow 

 into the English Channel, we find that it swings in a south-westerly direction 

 to the south of Yeovil and then westward along the north flank of the 

 Blackdown Hills, and thence along the centre of the Exmoor Range. 

 We have seen previously that starting at the Vale of Pewsey and going 

 east, the principal axis of folding lies farther and farther south, until we 

 reach the Battle axis north of Hastings ; and that going west from that 

 Vale the most important of the anticlinal axes lie farther and farther 

 south. In the extreme west the anticlinal axis of the Exmoor range is the 

 dominant structure. It will be observed that the water-parting behaves 

 in a closely similar manner. 



In accordance with the view herein expressed, I regard the Bristol 

 Channel as having come into existence as a definite basin by folding 

 during the Miocene period, and that the present form of the surface in 

 Devon and South Wales owes its origin to warping, during the same 

 period, of an ancient surface of erosion. 



It appears to me that the number of correspondences and analogies 

 between the physical features and particularly the drainage systems of 

 the south-east of England and those of the lands on both sides of the 

 Bristol Channel are so many and so close as to rule out mere coincidence, 

 and I believe that the only hypothesis which satisfactorily accounts for 

 them is the one which I have outlined. Whether the ancient surface was 

 eroded under marine or under continental desert conditions is still a 

 subject of uncertainty. There is no doubt, however, that the possibility 

 of desert denudation having played a leading part in its development has 

 a claim to serious consideration. 



As I stated at the beginning of my address, I have had to omit all 

 consideration of the later episodes which have given the Bristol Channel 

 its present configuration and coastal features. It may appear that in 

 the course of this address I have propounded more problems than I have 

 solved. It is my earnest hope, however, that I have sufficiently indicated 

 the interest and wide bearing of these problems, and that future workers 

 will turn to them and apply to their further elucidation the ever-increasing 

 knowledge and resources of our Science. 



