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



These beds of Liancourt contain also masses of sandy limestone 

 filled with chlorite : and Stubbington is remarkable for the quantity 

 of green earth which it contains. 



A circumstance is mentioned by the French authors which 

 appears to point out a remarkable era in the history of these strata. 

 They observe, that in the beds of the lower marine formation, and 

 particularly in those of Liancourt, natural wells of considerable 

 size are sometimes found, filled with ferruginous and sandy clay 

 and water-worn siliceous pebbles. These wells do not pierce 

 through all the beds of the calcaire grossier ; but begin at the 

 same level, and are covered and closed by the uppermost beds : 

 shewing that they were formed after the period of the formation 

 of the lowest, and before that of the upper beds ; which points out 

 a very long interval, and the action of violent causes during 

 this time. 



It may be remarked, that this is exactly the period to which we 

 must look for the subversion of the strata of the Isle of Wight, and 

 the formation of its basin. If therefore the deposition of the 

 upper beds of the calcaire grossier was general, and extended to 

 this part of the globe, it must be placed at the lowest part of the 

 Isle of Wight basin, and probably therefore at an inaccessible depth. 



The rocks of Bognor and Selsea appear to be the most easily 

 referable to some of the beds of the calcaire grossier of France. 

 The correspondence in their geognostic situation, in the nature of 

 their materials, and in the fossils which they contain, sufficiently 

 justify the supposition. 



Although in general the beds of the calcaire grossier maintain a 

 regularity remarkable and distinctly to be traced, yet that is not 

 always the case, the quarries of Salllancourt being cited as an 

 exception to this rule: all the beds are there united, and nearly of 



