164 



NEOZOIC TIME. 



[CHAP. x. 



Isle of Wight. 

 6. Tipper Chalk. 

 5. Middle Chalk. 

 4. Lower Chalk. 

 3. Upper Greensand ) 



and G-ault. j 



2. Lower Greensand, I 



or Vectian. / 



1. Wealden. 



Yorkshire. 



Upper Chalk. 

 Middle Chalk. 

 Lower Chalk. 



Eed Chalk. 



Speeton Clay, ) 

 . j 



France. 

 Senonien. 

 Turonien. 

 Cenomanien. 



Albien. 

 Aptien. 



upper 270 feet. 



Speeton Clay, \ Urgonien. 



lower 230 feet, j Neocomien. 



1. Stratigraphical Evidence. 



Lower Cretaceous. The Wealden Beds are restricted to 

 a comparatively small area in the south of England, and 

 do not extend far beyond the limits of the Purbeck Beds. 

 They occupy the country known as the Weald of Kent and 

 Sussex, and pass beneath the chalk hills which surround 

 this district, but they do not extend far to the north, for 

 the deep borings at Chatham, Erith, and Eichmond proved 

 their absence at those places. Eastward they reach below 

 the Straits of Dover into the Boulonnais, and westward 

 they spread beneath Hampshire and the Isle of Wight into 

 Dorsetshire, but have not been traced beyond Osmington 

 and Bidgeway. Southward they do not seem to have 

 reached so far as the present shores of France, for they 

 do not appear below the Aptien at the northern end of the 

 Pay du Bray inlier in Normandy. 



The Wealden Beds consist of thick lenticular alternations 

 of sand and clay, the sands being thickest in the lower part 

 and the clays in the upper part, so that they are usually 

 divided into (1) the Hastings Sand, and (2) the Weald 

 Clay. In the lowest beds (Ashdown Sand) layers of lignite 

 are not unfrequent ; the Wadhurst clay also contains lig- 

 nite as well as nodules of clay ironstone. In the sands 



