1822.] Geology of the Isle of JVight,&^c, 343 



The sandy cliffs, west of Christ Church Head, are traversed 

 by irregular subordinate argillaceous beds, some of which con- 

 tain calcareous concretions. The presence of organic remains 

 may be expected in such cases, though my very limited observa- 

 tions did not enable me to detect them. It is impossible to give 

 any description of the London clay without entering on details 

 which are incompatible with the objects of this notice. 



The natural section exhibited between Handfast Point and the 

 western termination of Hordwell Chff", not only affords a satis- 

 factory confirmation of the classification which has been adopted ; 

 but by a shght imaginary prolongation of the beds may be 

 linked to another natural section between Colwell Bay and the 

 Needles of the Isle of Wight. These general view^s enable us 

 to connect the great depositions on both sides of the Solent, and 

 to fix the relations of the vertical beds of Alum Bay by evidence 

 not short of demonstration. 



VI. Beds between the London Clay and the Lower 

 Freshwateii Formation. 



The vertical beds of Alum. Bay are succeeded by a formation 

 principally composed of siUceous sand ; the lower portion of 

 which is considerably inclined, while the upper portion is nearly 

 horizontal. It should seem, therefore, that this formation 

 belongs to the epoch of the great catastrophe which tilted the 

 central chalk range into its present unnatural position. The 

 section in Whitechff' Bay confirms this hypothesis. All its more 

 important features are beautifully delineated in the work of Sir 

 H. Englefield on the Isle of Wight ; and the accompanying 

 descriptions by Mr. Webster prove that its component parts are 

 contemporaneous, and probably continuous, with the formations 

 of Alum Bay. The two localities, however, diflfer from each 

 other in some points which are not unimportant. The lower 

 freshwater beds rest immediately upon the most northern ver^zca/ 

 bed of Whitecliff" Bay, and descend so rapidly to the level of the 

 beach that it is impossible to ascertain the nature of the strata 

 by which they are afterwards supported. Nor is this the only 

 distinguishing circumstance. The last vertical bed bears little 

 resemblance to the London day (D) of Alum Bay ; for it is 

 principally composed of siliceous sand, and contains a distinct 

 suite of fossils. I have no specimens of these fossils now before 

 me ; but from memoranda made upon the spot, they appear 

 chiefly to consist of the following genera : 



(1.) Ostrea, with a convex and deeply striated valve. 



(2.) Venus. 



(3.) Nucula. 



(4.) MureXj two species. 



(5.) Rostellaria rimosa, 



(6.) Cerithiuniy one or two species. 



{V») Ancilla subulatafKc. 



