186 Mr. Webster o« /y&^ Strata lying over the Chalk, 



tent and thickness. They extend quite across the island in a vertical 

 position, keeping parallel to the chalk, and appearing again at White- 

 clifF bay on the east end, where they are however much concealed 

 by grassy slopes. 



All along the north side of the range of chalk hills which extends 

 from Handfast-point through Corfe Castle, there is an extensive 

 stratum of pipe clay in a horizontal position. It contains a bed of 

 coal so exactly resembling that of Alum bay, that this circumstance, 

 added to the quality of the clay and its geognostic position, is suf- 

 ficient to identify it. 



I have been favoured by Alexander Jaffray, Esq. with the follow- 

 ing section of the clay pits of Norden, near Corfe. 



Sand on the top - - - 



10 



feet 



Blackish brown clay 



14 





Wood coal - - - - 



3 





Refuse clay . . - - 

 Fine white potter's clay 

 Dark brown clay - - 



5 

 6 

 2 





Fine white potter's clay 



Q\ 





461 



The same stratum of clay, though not of equal quality, may be 

 traced in the hills near Poole ; and is found in many parts of that 

 extensive tract called the trough of Poole. 



Potter's clay, white, yellow, or greyish white, similar to that In 

 the Isle of Wight, is also frequently found in the London basin : 

 some of it is of considerable fineness, as on the east bank of the river 

 Medway, near Rochester. 



The plastic clay is frequently of a deep red colour, or red and 

 white mottled, as in Alum bay : a similar red clay is dug near 

 Portsmouth and other places along the South Downs. It also ap- 

 pears at Reading. 



