1849.] AUSTEN ON THE VALLEY OF THE ENGLISH CHANNEL. 97 



ting no great moving power, seem to require some such agent as that 

 of floating ice to account for their position. 



Terrestrial conditions of great geographical extent, and of long 

 duration, intervened between the oolitic and cretaceous periods : the 

 Wealden strata of Sussex, Isle of Wight and Dorset indicate clearly, 

 by the interchange of marine and freshwater conditions, that the 

 Wealden area was at the sea level, or at the lowest portion of the 

 area of dry land to which it was subordinate. It is not necessary to 

 consider the direction of the dry land of the period ; it is sufficient 

 that no beds of the Wealden age underlie the Neocomian deposits 

 from Trouville to Cape la Heve : the slight and even questionable 

 traces of the Wealden in the Boulonnais show that it had its limit in 

 that direction. The palaeozoic series of the Boulonnais had received, 

 long prior to this, the features of elevation and folding which it 

 now presents ; the line of this disturbance extends eastwards : if pro- 

 longed west it would pass along the English Channel, which, being 

 occupied by the lower oolitic groups, whilst the Boulonnais presents 

 only the middle and upper, prove it to have been relatively an area 

 of depression. 



Coarse rounded shingle formed of local materials, such as of the 

 siliceous bands of the carboniferous deposits, occurs abundantly at the 

 base of the greensand beds west of the Haldon Hills. The equiva- 

 lent beds in the Cotentin are also a shallow-water accumulation. 



Terrestrial conditions again obtained during the course of the eocene 

 accumulations ; but the freshwater deposits of Hampshire and the 

 Isle of Wight, and which are entirely included in the area of the 

 present Channel, indicate, by the alternation of marine, brackish, and 

 freshwater conditions, a like position with respect to the area of eocene 

 dry land, which the Wealden lake had presented before at the same 

 place. 



VOL. Yl. PART 1: 



