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



The stratum marked A, is chalk with flints,* which at the 

 north side is in nearly vertical layers, the inclination becoming gradu- 

 ally less and less towards the south side, where they dip about 60°. 

 B is chalk without flints. 

 C chalk marl. 



D calcareous sand-stone, with subordinate beds of limestone and 

 chert. 



E bluish-black marl. 



F ferruginous sand and sand-stone, with potters' clay, slate clay, 

 argillaceous limestone, wood-coal, &c. The part of this stratum in 

 the middle ranges of hills inclines only a few degrees, extending to 

 the south side of the island, where it is horizontal. It is to be re- 

 marked, that towards this side of the island there is a higher range 

 of hills H, composed of horizontal strata which correspond ex- 

 actly with a part of those of the highly inclined series of the middle 

 range, not only in their nature, but in their order of superposition ; 

 thus irresistibly forcing upon us the conclusion, that they belonged to 

 the same formation, and that they had probably at some period been 

 continuous. 



The strata G, to the north of these already mentioned, consist of 

 a numerous alternating series in a vertical position, and are com- 

 posed chiefly of sand and clay. These may be seen to great advan- 

 tage in Alum bay, where they form cliffs about 200 feet in height. 



The whole of the most northern part of the island, I, consists of 

 nearly horizontal strata, which come up abruptly against those that 

 are vertical, but are slightly curved at their junction with the latter. 

 These, however, proved to be entirely different in their mineralogi- 

 cal characters and in the fossils which they contained, from the strata 



* It was this chalk, together with the verUcal strata of Alum bay, and the horizon- 

 tal strata on each side, that were first observed and described by Sir H. Englcficld. 



