﻿660 MR. H. BURY ON THE DENUDATION OF [Nov. I9IO,. 



from it. If I am correct in supposing that the warped plain felL 

 away both east and west of Botley Hill, then the lower passage 

 across the Chalk of the Medway and the Mole may have been one of 

 the factors which led to the superiority of these rivers over their less 

 fortunate neighbours, the Darent and the Wandle. The predomi- 

 nance of the Medway, however, extending as it does behind the Stour 

 as well, cannot be wholly explained in this manner. Some of its 

 advantage may be derived from the change of strike which (even 

 if there be no true anticline) would reduce the level of the Chalk 

 over which it flowed by forming in it a re-entering angle ; and there 

 is also the syncline in the Lower Greensand (26, p. 277) to be 

 considered. The Medway, however, lies outside the scope of this 

 paper, and I merely draw attention to these possible factors in its 

 success, without attempting to determine their relative importance. 



The effect of transverse folds on an antecedent drainage-system 

 presents much the same difficulties as in the case of the longitudinal 

 folds ; but, if the folds were shallow (as they seem to be), and the 

 rivers well established, I cannot see any probability that the main 

 consequent lines of drainage would be much affected, except where 

 fold and river happened to coincide : and this, unless the river- 

 system was still very immature, would seldom happen. 



There are several recognized instances (26, p. 277) of the coinci- 

 dences of rivers with transverse synclines, and others (7, p. 406 ;: 

 24, p. 10 ; 29, p. 431) in which the facts are more or less disput- 

 able ; but I know of no such syncline unconnected with a river, 

 so that contemporaneity of river and transverse fold is strongly 

 indicated. Now, the transverse disturbances are considered by 

 Dr. Barrois (1, p. 115) to be later than the longitudinal, and 

 Mr. Young (29, p. 435) has given an instance in which this is 

 certainly the case. If, then, we accept Dr. Barrois's opinion on 

 this point, it follows that the longitudinal folds are antecedent to> 

 the rivers. This accords very well with the hypothesis of marine 

 planation in Pliocene times, but is opposed to continuous subaerial 

 denudation since the close of the Eocene. 



There are said to be two rivers running along transverse anti- 

 clines, the Medway (27, p. 350) and the Cuckmere (1, p. 23). 

 I am not in a position to affirm the accuracy of these inferences,, 

 but accepting them as correct, the hypothesis of prolonged sub- 

 aerial denudation, whether the rivers were contemporaneous with 

 or antecedent to the folds, affords no satisfactory explanation. If, 

 on the other hand, we assume that marine planation followed the 

 formation of these two transverse anticlines (and Dr. Barrois spreads 

 them over a long period), the problem ceases to afford any further 

 difficulty. 



While, therefore, it would be very rash to draw conclusions from 

 the relations of rivers to the folds without collateral evidence, yet 

 it is legitimate to claim that they do, on the whole, support a belief 

 in a period of marine planation which was subsequent to most of 

 the longitudinal folding, and immediately antecedent to most, 

 though perhaps not quite all, of the transverse disturbances. 



