Plastic Clay Formations of the Isle of Wight. 



171 



Beyond this point, the freshwater strata, abounding in Potamides and other cha- 

 racteristic shells, occupy the remainder of the space represented in the diagram. 



The result of this examination is, that we tind a complete alternation of the Lon- 

 don and plastic clay formations throughout the whole space of 525 paces from the 

 chalk to the break at/ e, as we not only have abundance of London clay fossils at 

 the place marked e, which corresponds with the great mass of that formation in 

 Alum Bay, marked B in Mr. Webster's section, but we likewise find them at the 

 points marked h, and at h*. At k we again meet with the Venericardia planicosta 

 and other characteristic shells f. 



Having terminated our examination in White Cliff Bay, we next directed our 

 attention to the corresponding out-crop at Alum Bay ; but before proceeding to 

 describe the beds, it is necessary to mention that the diagram No. 2. is copied from 

 Mr. Webster's, in vol. ii. of the First Series of the Transactions. It includes the 

 London clay B, which adjoins Headon Hill, and the coloured sands beneath it, 

 down to the chalk marl a. I have inserted the letters of reference used by Mr. 

 Webster in his paper on these formations, that reference may, if necessary, be 

 made with greater facility to his descriptions of the strata. But as a detailed 

 account of the whole of the beds described by Mr. Webster is not the object of the 

 present notice, I have therefore divided the space into nine portions, commencing 

 at the chalk marl and proceeding towards the London clay B ; the following is the 

 order of superposition : the beds in the section are in the inverse order to those 

 in White Cliff Bay : 



ALUM BAY. 



Chalk 



London Clay. 



1. Yellow sand 



2. Variegated clay 



3. Dark greenish gray sand, containing Cancer Leachii, etc 



4. Dark greenish clay, containing abundance of London clay fossils 



5. Dark greenish gray sand, with veins of clay 



6. Same sort of clay as No. 4 



7. Variegated sands and clays without fossils 



8. Gray and brownish clays without fossils 



9. London clay, commencing with a band abounding with Nummulites and minute shells 



2 1 



Paces. 

 2 



35 



3 

 58 



9 



16 



252 



12 



83 



f In the section of White Cliff Bay, p. 170, I have carefully abstained from tinting any part of the 

 cliflFs, excepting those portions which retain their original positions. The back cliff and disrupted portions 

 are expressed by outline only. 



z 2 



