168 Mr. Webster on the Strata lying over the Chalk. 



The chalk of the middle hills of the Isle of Wight dipping to 

 the north, and that of the South Downs dipping to the south, it 

 was an obvious inference that it might pass under the channel called 

 the Solent, thus forming a basin. This idea was rendered still 

 more probable on finding that the bottom of this channel consisted 

 mostly of the London clay, which stratum is found under Ports- 

 mouth, whence it may be traced eastward, forming the lowermost 

 bed next the sea all along the shore of Sussex to Pagham and Bognor, 

 and westward to Stubbington cliff, and along the coast of Hamp- 

 shire to Hordwell and High cliffs. In all its characters and fossils, 

 this bed was found to agree with the blue clay which lies over the 

 chalk, in the counties of Kent, Surrey, Middlesex, Essex, &c. and 

 with the most northerly of the vertical beds of Alum bay.* Besides, 

 the chalk itself lies at no great depth from the surface in all that 

 part of Sussex south of the South Downs, and is even found on 

 the shore at lowwater-mark at Middleton, two miles east of Bognor. 



It appears, therefore, that between the vertical chalk-hills of the 

 Isle of Wight and the South Downs there is a basin or hollow, 

 occasioned by the disturbance of the whole mass of strata from 

 below the chalk to the London clay, inclusive : and also that this 

 disturbance took place at a period subsequent to the deposition of the 

 last-mentioned stratum, since it is amongst those which have suf- 

 fered a change of position. 



From this it will be readily admitted, that all the beds situated 

 within this basin lie above the London clay, and are posterior to it. 

 Of this description are the horizontal beds of the most northerly 

 part of the Isle of Wight ; and since they come almost into contact 



* Having by the kindness of Mr. Ilolloway, of Portsmouth, become familiar wi(h 

 the fossils of Stubbington, I readily perceived their agreement with the above-mentioned 

 »(ra(um in Alum bay. 



I 



