﻿MURCHISON FLINT DRIFT OF S.E. ENGLAND. 



375 



But to return to the escarpment of the North Downs. In look- 

 ing at the fracture, dismemberment, and great denudation of the chalk 

 and tertiary strata near Farnham, we have before us a very adequate 

 cause to explain the abundant local distribution of such detritus. In 

 short, the angle which the North Downs here makes with the Hamp- 

 shire or Selborne escarpments has probably been the scene of still 

 greater rupture than that to which allusion has been made to the 

 west of Petersfield, where the latter range is confluent with the chalk 

 of the South Downs. 



In looking to the present drainage of the county, and in perceiving 

 that the western tributaries of the Wey flow along the south side of 

 the Hog's Back, or parallel to the axis of the chalk-ridge on the one 

 hand and to the Wealden on the other, we have before us somewhat 

 of the same geographical feature as that before described, on the other 

 side of the great Wealden axis, where the river Rother flows from a 

 depression in the chalk west of Petersfield. 



For some miles between Farnham and the environs of Godalming, 

 I am not aware of the existence of any drift ; but the Lower Green- 

 sand, particularly that portion of it which is charged with iron- 

 stone-bands or "clinkers," has been powerfully denuded, and is 

 always near the surface. In proceeding farther eastwards along the 

 longitudinal depression, leaving the hills of chalk on the north or left 

 hand, i. e. to Compton and Godalming, we reach the depression called 

 Pease Marsh, where, owing to a former excavation, to which I do 

 not now refer, the whole of the greensand which surrounds it was 

 removed, and the Weald Clay first denuded and afterwards covered by 

 copious accumulations of gravel and clay. That the Weald Clay con- 

 stituted, at the period of the spread of the debris under consideration, 

 a true terrestrial surface*, was first suggested by Mr. Austen, who 

 has detected thereon, and beneath all the detritus, stumps and stems 

 of forest-trees, the former vertical, and as if in a growing position. 



As the detritus of Pease Marsh occasionally presents somewhat of 

 stratified appearances, more indicative of regular deposition under 

 water than the drifted materials, to which allusion has already been 

 made ; and as Mr. Austen, who recently pointed out to me the leading 

 features of the deposit f, entertains opinions respecting the origin of 

 this detritus differing from my own, I beg permission to enter into a 

 little detail, the more so as a communication formerly made by my 

 friend to the Geological Society, and relating to this very point, has 

 never been communicated to the public. 



The patch of detritus in question is not merely confined to the 



* Vide supra, p. 288. In consequence of this Memoir taking its place at the 

 end of the present volume (its publication having been unavoidably deferred), and 

 Mr. Austen's Memoir, On the Valley of the Wey, as well as the Papers on the 

 Folkestone Bone Bed and the Sangatte Cliff, by Mr. Mackie and Mr. Prestwich 

 respectively (in each of which Memoirs detailed accounts are given of phaenomena 

 alluded to in the present Communication), having already appeared in the Quar- 

 terly Journal of the Society, references are here made to the above-mentioned 

 Papers whenever required. 



f See the Memoir alluded to in the preceding note ; read June 25, 1851. Vide 

 supra, p. 278 et seq. 



