﻿668 MR. H. BURY ON THE DENUDATION OF [Nov. 1910, 



modification of the views expressed in my former paper (2) 

 as to the origin of the Farnham River. The western part of it 

 I still regard as having originated on Chalk, but some of its 

 eastern end must have arisen in the softer Lower Cretaceous beds, 

 and it is not easy to know what limits to assign to the two 

 portions. It is perhaps significant that, although the Alice Holt 

 gravels lie close to the crest of the anticline, the river to the west 

 of Bentley departs altogether from that line, which is continued, 

 with ' diminished intensity, through Upper Froyle, Holybourne 

 Down, etc. (12, p. 48). In order to make clearer my own con- 

 ception of the evolution of this river- system, I have ventured in 

 fig. 5 to indicate the position of several early consequents, in 

 relation to the existing streams ; and at the same time I have tried 

 to show the limits of the Chalk upon the marine plain, as com- 

 pared with its present escarpment. When due allowance has been 

 made for the wide margin of error inseparable from such an attempt, 

 the development of the existing river-system from the marine plain 

 presents no special difficulties. The extension of the Chalk is 

 perhaps somewhat greater than might have been expected, but 

 between the southern limit assigned to it and the crest of the 

 Farnham anticline (say, roughly, the village of Wrecclesham) the 

 strata are extremely level, so that planation would probably leave 

 nothing but a thin layer of Lower Chalk ; this would be cut into 

 narrow strips by the numerous consequent rivers, and so, all things 

 considered, its removal would be rapid. We are not obliged to 

 determine the relative parts played by the sea and by rivers in 

 producing the small amount of chert found on the Farnham Plateau 

 and north of Bentley ; but the Dippenhall drifts point to the survival 

 of the Crondall consequent, until a valley had been excavated 

 about 200 feet below the level of the plain. 



If, on the other hand, we adopt the subaerial theory, without any 

 assistance from the sea, we are obliged to attribute all the chert 

 found north of the Farnham Valley to consequent rivers. It 

 follows, then, that there was an early period of denudation, prior to 

 the exposure of the Hythe Beds at Hindhead, which has left no 

 distinct record behind it ; and a second period to which all the 

 remaining drifts belong, those of the Farnham Plateau (late 

 Pliocene ?) being the earliest. For convenience, I shall speak of 

 these two periods as the first and the second cycle, without in any 

 way implying a physical break between them. 



We have no means of deciding at all closely the position of the 

 Chalk escarpment at the end of the first cycle, but it is evident that 

 the cycle must have been a long one, since the exposure of the 

 Hythe Beds at Hindhead involves the removal of about 1000 feet 

 of strata (26^ p. 217) without counting the Eocene beds. On the 

 other hand, in the second cycle Hindhead has apparently not been 

 lowered more than 50 feet ; and it is, therefore, somewhat surprising 

 to find that at the beginning of this period (and even for some 

 time later) the river-system was in a very immature state. The 

 distribution of chert shows that the Farnham River did not exist, 



