﻿Vol. 64.] ME. H. BURY OjST THE EIVER WEY. 325 



of the middle ridge ; and I have no hesitation in ascribing a similar 

 origin to the gravels of Eowledge and the southern ridge. 



The patches of drift scattered over Alice Holt I have had no 

 opportunity of studying in section, but from examination of the 

 surface-material I sliould judge their composition to be very similar 

 to that of the Eowledge gravels — certainly Lower Greensand 

 pebbles are present in greater quantity than on the northern ridge. 



In ascribing all these drift-beds to one river, which also planed 

 down the underlying Gault and Lower Greensand, I am running 

 counter to the teaching of the maps of the Geological Survey, on 

 which only the gravel of the northern ridge is described as ' River- 

 Gravel,' while all the other beds are classed as ' Gravel and Sand of 

 uncertain age and origin.' I do not know the grounds for this 

 distinction, but perhaps the following passage from Topley's 

 ' Geology of the Weald' (p. 196) throws some light upon it : 



' FHuts are scattered about over the high land of Farnhatn, Frensham, and 

 Thursley Commons,^ and over Alder Holt; but these are probably the remains 

 of the Chalk which once covered the lower beds and are not a deposited 

 gravel.' 



This, of course, was written before Monckton's & Mangles's recog- 

 nition of some of the beds as of fluviatile origin ; but, quite apart 

 from that, it should have been obvious that mere disintegration of 

 the Chalk and Upper Greensand could not plane down the lower 

 strata to one level, and that this planing is conclusive in favour of 

 river-action. 



But, although the formation of this plateau by a river admits of 

 no doubt, yet it is not at once obvious what the course of that river 

 was. At the present day we find the Farnham River immediately 

 on the north, and the Tilford River on the south, with no vestige in' 

 either case of a former watershed which would enable us to identify 

 our plateau-river with either. It is true that the gravel of the 

 northern ridge is continued for a short distance down the slope of 

 the Earnham Valley, while on the southern ridge the drift hardly 

 extends to the edge : but that, of course, is not conclusive, and on 

 the other hand the tendency, already noted, of the whole plateau 

 to slope south-eastwards might be held to point to the Tilford 

 stream as the modern representative of the plateau-river. The key 

 to the problem lies, I think, in the junction with the old consequent 

 river which we have already traced : for, while it is easy to under- 

 stand how this junction might shift downstream (that is, northwards) 

 it hardly seems possible for the Tilford River, if it formerly joined in 

 as far north as the plateau extends, to have shifted its point of 

 junction upstream to Tilford. We have already seen reason to 

 believe that the consequent river was not beheaded till a lower 

 level than the plateau had been reached ; and I wdll now add some 

 further evidence pointing in the same direction. 



Each of the three ridges of the plateau, after maintaining for a 

 considerable distance the plateau-level (of which 350 feet may be 



^ Farnham Common embraces the eastern ends of the three ridges ; Alder 

 Holt is the name erroneously substituted for Alice Holt on the old Ordnance- 

 Survey map. 



