﻿Vol. 66. .] THE WESTERN END OF THE WEALD. 689 



insisted on in this paper, and the composition of the Southern 

 Drift. It seems to me in the highest degree improbable that 

 existing rivers could, on a Chalk soil, oscillate sufficiently to account 

 for this distribution ; or that, if they did so, they would have 

 sufficient carrying power to transport the bulky material of which 

 the Drift is often composed. I am aware that the Black water has 

 carried chert several miles to the west of its passage across the 

 Chalk; but the conditions are quite different: the river-curve in 

 that case is on an Eocene soil, and by the time that the Loddon is 

 reached the chert fragments are invariably small. Lastly, I may 

 point out that the curve of the crest of the escarpment (though 

 without, it is true, any present connection with the river-system) 

 is very conspicuous on the Hog's Back, where the Chalk can hardly 

 be supposed to have formed part of a post-Eocene plain, subaerial 

 or marine. Some other cause, therefore, than the one just sug- 

 gested, must be found for the peculiarities of the Downs and their 

 relation to the subsequent rivers ; whether, however, there are 

 structural features which have hitherto escaped notice, or whether 

 solution of the Chalk, acting more forcibly in the neighbourhood of 

 the transverse rivers, could produce such large effects, I must leave 

 others to determine. 



The absence of any definite longitudinal consequent streams 

 forbids us to assume that the rivers and longitudinal folds originated 

 at the same time, and where connection exists between stream and 

 ssyncline it has probably been arrived at, more often than not, as 

 the result of a movement of the former down the dip-slope while 

 the escarpment retreated before it. A similar movement has 

 possibly more than once obscured early connections between longi- 

 tudinal anticlines and subsequent rivers, as, for example, between 

 Bentley and Farnham, where the high-level gravels still mark the 

 former coincidence. On the other hand, there is strong reason to 

 believe that the early success of the Wey and the Adur was in no 

 small measure due to the exposure of soft beds along the planed-off 

 crests of longitudinal anticlines. The evidence then, on the whole, 

 points to the main longitudinal folds having preceded planation, 

 though some further movement along the North Down line accom- 

 panied the upheaval of the plain ; but the transverse movements, 

 which in some cases at least are of later date than the longitudinal, 

 often show a connection with the rivers which is best explained by 

 the hypothesis of contemporaneity. Thus the Arun and the Adur, 

 or perhaps the Wey, the Darent, and the Stour, pass through the 

 Chalk in transverse synclines ; a similar syncline coincides with 

 the passage of the Medway through the Lower Greensand ; and the 

 old valleys of the Blackwater and the Merstham stream, as well 

 as the Seale stream, are closely connected with transverse faults. 

 Perhaps, too, we may associate with this cause the change of strike 

 which accompanies the consequent trunks (past or present) of the 

 Blackwater, the Mole, and the Adur, as well as the long straight 

 watershed which separates the Mole from the Wey, including those 

 streams which have been captured from the latter by the Arun. 



