66 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



represented by our S.E. counties, and along a line to the N. of the 

 "Wealden denudation. 



To what extent the Oolitic group may exist beneath the Wealden 

 and Cretaceous groups of Kent, Sussex, and Surrey, is a more difficult 

 question ; but, the continuity of the old ridge being granted, we may 

 infer that, relatively as to its breadth, it exercised along our area a 

 like influence to that it had along its continental course, and that, 

 whilst the ascending members of the group were brought up against 

 it by a process of successiye overlap, as in the Boulonnais, so also 

 they were abraded and denuded from above downwards, as has hap- 

 pened there. We shall see reasons for assuming that such a con- 

 dition of surface existed, when noticing the composition of the Lower 

 Cretaceous sand-group. 



§ 3. Wealden Series. 



I suggested in 1850* that the so-called Wealden strata would be 

 found to be referable to two distinct geological periods of time, — the 

 Oolitic and Cretaceous ; and, apparently, from the movements which 

 took place in the Western European area at those times, the secondary 

 lacustrine series of the South of England corresponds with the 

 Upper Oolitic and Lower Cretaceous or Neocomian group, whilst to 

 the N. it may be the equivalent of older portions of the Oolitic 

 series. 



In the course of an excursion into Belgium in 1852, together 

 with several members of this Society — the late Prof. E. Forbes, Mr. 

 D. Sharpe, Mr. Prestwich, and Mr. Tylor, — we were shown by M. 

 Dumont an old land-surface near Tournay, in an intermediate posi- 

 tion between the Carboniferous Limestone and the lowest Cretaceous 

 beds ; again, near Mons, we were conducted by Mr. Lambert to a 

 most striking instance of such conditions. Both these localities 

 occur in that area which was dry land during the whole of the Per- 

 mian, Triassic, and Oolitic periods. The evidence as to age from the 

 contents of these beds has not as yet been worked out. 



The lowest strata exposed in our S.E. counties belong to the 

 Secondary lacustrine series ; of this, the portion known as Weald 

 clay may be seen on the W., as at Punfield, in Swanage Bay, to 

 alternate with, and therefore be synchronous with, the marine Neo- 

 comian group f. No Neocomian beds occur anywhere W. of Pun- 

 field whilst Wealden strata do ; and, as freshwater formations imply 

 subordination to land-surface, it is clear that the direction in which 

 it lay must have been W. and S. at the time when that subsidence 

 was taking place which brought the Neocomian sea-group into the 

 area of the Wealden lake. 



Some beds in the Boulonnais which immediately overlie the Port- 



* Quart. Journ. Geol. Soc. vol. vi. p. 467. 



t The evidences of this were brought before the Geological Society in 1850, 

 and I gave the fossils to the Jermyn Street Museum, it being the intention of my 

 friend the late Prof. Edward Forbes to have described them in his account of the 

 Purbeck and Wealden deposits. 



