PITTON S SECTION AT ATHERFIELD. 



Fig. 3. Fig. 4. 



mm 



291 



Black- Gang Chine. 



Whale and Walpen Chines. 



Vndercliffs. — The picturesque scenery at the back of the Isle of 

 "Wight, emphatically called " the UndercliiF," is a most striking ex- 

 ample of the structure, or rather destruction, produced by the alterna- 

 tion of solid or permeable strata with others more retentive of moist- 

 ure. In the present section, some cases occur of less prominence, but 

 not undeserving of notice. Looking eastward, from the top of the 

 cliif, near Atherfield, towards Rocken End, the strata are seen to rise 

 conformably at a very small angle of inclination ; but their uniformity 

 is broken by two or three less regular shelves, and these upon exami- 

 nation are found to have been produced by certain retentive beds 

 among the looser strata. The water thus kept up carries off a part 

 of the lower mass, undermining that above ; and the result is the pro- 

 duction of a shelf or terrace, between two ranges of cliffs, one of them 

 supporting " the Undercliff," the second forming a remoter vertical 

 face behind. 



Six or seven of these minor undercliffs formerly existed on the 

 coast between Atherfield and Rocken End, one of which (near Ather- 

 field) has now nearly disappeared. The most remarkable of those 

 which remain is due to a group of clay and retentive sand, in which 

 Captain Ibbetson was the first to discover several species of fossil 

 shells, and which is for the greater part concealed by ruins of the 

 upper strata. The underclifP upon this clay rises nearly at Walpen 

 Chine, ascending westward and crossing Ladder and Whale Chines. 



Another marshy undercliff, which comes down to the shore on the 

 east of Cliff-End, has been produced by the fall of the white sand and 

 clay No. 41, a small portion only of which is visible near Walpen 

 High-cliff : and still other alternations of clay and sand in the beds 

 above have cooperated with the Gault in producing the fall of the 

 upper greensand, by which enormous masses of that deposit have 

 been brought down, even to the sea-side, at Rocken End. 



Divisions of the Section. 



The whole series of deposits here consisting of sand and clay, with 

 great uniformity of aspect, the most obvious divisions might be derived 

 from their difference in mineral composition. The list of strata which 

 I have adopted is therefore in some measure arbitrary, and intended 

 chiefly to facihtate reference to this particular section ; and I cannot 

 too strongly caution my reader against supposing that similar sub- 

 divisions of groups, which in a geological sense are the same, are to 

 be expected in other places, especially when the distances are great. 

 It will presently be seen that within the Isle of Wight itself, the 

 distant portions of continuous beds vary considerably in character: 



