204 



LYELL'S ELEMENTS OF GEOLOGY. 



Position of Wealden. 



Fig. 191. 



Cone from the Isle of Purbeck, 

 resembling the Dammara of 

 the Moluccas. Fitton. 



Sphenopteris gracilis (Fitton), from 



near Tunlridge Wells. 

 a. portion of the same magnified. 



clay passing beneath the green-sand in various parts of Surrey, 

 Kent, and Sussex ; and if we proceed from Sussex westward to 

 the Vale of Wardour, we there again observe the same forma- 

 tion occupying the same relative position, and resting on the 



Fig. 193. 



Vale of Wardour. Wilts. 



Hants. 



Sussex. 



Wealden. 



Wealden. 



oolite. (See Fig. 193.) Or if we pass from the base of the 

 south downs in Sussex, and cross to the Isle of Wight, we there 

 again meet with the same series reappearing beneath the green- 

 sand, and we cannot doubt that the beds are prolonged subterra- 

 neously, as indicated by the dotted lines in Fig. 194. 



Isle of Wight. 



It has been already suggested that, during the accumulation 

 of the green-sand, there was a gradual sinking down and sub- 

 mersion of land, by which the wide open sea of the chalk was 

 produced. But the position of the Wealden points still more 

 forcibly to such a conclusion, and especially the appearances 

 exhibited at the point of junction of the wealden, and the oolitic 



