Geological Society of London. 581 



2. " On the Evidence afforded by the Detrital Beds without and 

 within the North-eastern part of the Valley of the Weald as to the 

 mode and date of the Denudation of that Valley." By S. V. Wood, 

 Jun., Esq., F.G.S. 



The author commenced by discussing the various hypotheses that 

 have been proposed to explain the denudation of the Weald Valley. 

 In his opinion the upheaval of the district took place in Postglacial 

 times, and subsequently to the deposition of the gravels of the 

 Thames Valley, of East Essex, and of the Canterbury heights ; and 

 the denudation was effected chiefly by tidal erosion during gradual 

 upheaval in an inlet of the sea, aided by the action of fresh water 

 flowing into this inlet from the north by streams draining the land 

 which now constitutes the counties of Middlesex and Essex. The 

 chief evidence in favour of his views is as follows : 1. The absence 

 from the Glacial beds of Essex of any debris representing a consider- 

 able denudation of the Weald during the Glacial period, and the 

 probability that the Wealden area was beneath the sea during the 

 deposition of the Boulder-clay. 2. The comparative absence of 

 Lower Cretaceous or Hastings-sand materials from the Postglacial 

 gravel-sheets outside the north of the Weald. 3. The impossibility 

 of reconciling the presence of Tertiary pebbles in certain Weald- 

 gravels with an origin by means of streams flowing in the direction 

 of the present rivers. 4. The antagonism between the character of 

 the major valley of the Weald and that of any excavation producible 

 by the agency of rivers. 5. The persistence of the old coast contour 

 with the river- drainage entering it from the north. 6. The existence 

 of a cause, in the shape of an isthmus at Dover, sufficient to induce 

 a strong tidal scour. 



Discussion. — Mr. Godwin-Austen tliouglit that the author had done his theoiy 

 injustice in presenting only a portion of the "Wealden area for consideration. He re- 

 marked that phenomena similar to those of the Weald were to be found in various 

 parts of "Western Europe. He was glad to find that Mr. Searles "Wood did not regard 

 the escarpment as representing marine cliffs ; but he did not attach sufiScient weight 

 to the absence of any material of marine origin at their base ; so that there was no 

 evidence of the presence of the sea within the "Wealden area. He differed wholly 

 from the author as to the age of the gravels ; for beneath the gravels were silty beds 

 containing Elephant-remains. These gravels he was inclined to refer to a Glacial 

 ■ period, as they contain blocks such as could only have been transported by the agency 

 of ice. The elephants found in the valley of the Wey are of the species E. primi- 

 genius, which also occurs in the Selsea beds ; and he believed both to be of Glacial 

 age. As to the theory of the denudation of the "Weald, he professed himself a con- 

 vert to the views of Messrs. Foster and Topley, and cited what was now going on 

 in Heligoland in illustration of atmospheric denudation. 



Mr. "Whitaker observed that the present absence of gravels along parts of the 

 vaUey of the Thames affords no proof of their not having formerly existed. He 

 pointed out the soft and friable nature of most of the rocks of the "Wealden, which 

 would account for their absence in the gravels. The only really hard rock was the 

 Chert of the Lower Greensand, which was abundant in the gravels of "West Kent. 

 Angular flints occurred at the base of the chalk escarpment wherever it had been 

 carried back by denudation. The major valley of the "Weald had been spoken of; 

 but he denied that any such valley existed ; it was merely a series of numerous small 

 valleys. He could not conceive the rivers flowing against the dip of the strata, as 

 supposed by Mr. "Wood. He did not agree in the view of the denudation of the 

 "Weald being such an enormous affair, but thought that it might be due to compara- 

 tively small causes. 



