152 PROF. EDWARD HULL, LL.D., F.R.S., P.G.S., ON 



Professor Hull. — Very much so, yes. I am much pleased with the 

 discussion, and I am especially pleased that Dr. Jack is able to 

 coincide with the views I have put forth. 



What he says with regard to the dependence of natural physical 

 features and independence is perfectly true, and it is sometimes very 

 difficult to know why we have both. In such a case as the table- 

 lands of Cornwall and Devon, the independence of the features is a 

 matter which we know is very remarkable and originates from the 

 enormously powerful action of the ancient ocean during the times of 

 the subsiding and emergence of the land. On the other hand, we 

 have features such as those of the Cotteswold Hills, not so very far 

 off, in which the dependence of the features is capable of explanation 

 hy the character of the strata. For instance, in the case of the 

 Cotteswold Hills, we have first the plain of Gloucester, and then it 

 gradually rises in this way [e^.plaining on the blackboard]. Beyond the 

 escarpment of the Cotteswold Hills we have another plain, the upper 

 plain being formed of Oolite limestone ; the whole plain of 

 Gloucester being formed of the Lias clay. So that the dependence 

 of the escarpment of the Cotteswold Hills is clearly due to the 

 superior hardness of this mass of limestone, which is about 250 feet 

 and 300 feet in thickness, superimposed on the soft shales and other 

 strata on which it rests. This limestone was originally covered 

 over by newer strata to a height we do not know ; but what remains 

 of this table-land is the result of a horizontal denuding agency when 

 exposed to the waves of the sea and subsequent subaerial erosion. 



Then we have a second plain of marine denudation in this valley 

 of the Severn and the plain of Gloucester, by which the strata of the 

 Cotteswold Hills have been eroded back from their original margin. 

 So in this case we have a repetition of the effect of the dependence 

 of the conditions of the strata for their physical features and 

 independence in such cases as those of Devon and Cornwall. 



Now Dr. Jack does, I think, very clearly indicate the difference 

 between denudation which produces a plain surface and denudation 

 which produces valleys, and I have been endeavouring for many years 

 to maintain that you cannot have a great plain of strata, more or less 

 elevated, without bringing in the action of the ocean. On the 

 other hand, the valleys, as everyone admits, are the result of the 

 erosive action of running water. But there are geologists in the 

 present day who will not admit that these islands were submerged 



