Ch. XXII.] VERTICAL STRATA OF ISLE OF WIGHT. 31 5 



tion of the above theory to the region immediately westward 

 of the great line of chalk escarpment which runs through the 

 central parts of England from Dorsetshire to Cambridgeshire. 

 The denudation in that country has doubtless been on a great 

 scale, and was, perhaps, effected during the Eocene period ; 

 for we know of no reason why one line of movements should 

 not have been in progress in a direction north-east and south- 

 west, while others were heaving up the strata in lines running 

 east and west. We may remark, at the same time, that if the 

 chalk in the interior of England, in those tracts from which it 

 has been extensively swept away, began to rise during the ter- 

 tiary epoch, and before the emergence of the chalk which once 

 extended over the central axis of the Weald, some tertiary 

 deposits may, in that case, have been thrown down upon that 

 central ridge. We have at present, however, no data to lend 

 countenance to such conjectures. 



Vertical strata of the Isle of Wight. A line of vertical and 

 inclined strata running east and west, or parallel to the central 

 axis of the Weald, extends through the isles of Wight and 

 Purbeck, and through Dorsetshire, and has been observed by 

 Dr. Fitton to reappear in France, north of Dieppe. The 

 same strata which are elevated in the Weald Valley are up- 

 heaved also on this line in the centre of the Isle of Wight, 

 where all the tertiary strata appear to have partaken in the 

 same movement *. 



From the horizontality of the fresh-water series in Alum 

 Bay, as contrasted with the vertical position of the marine ter- 

 tiary beds, Mr. Webster was at first led very naturally to 

 conclude, that the latter had undergone great derangement 

 before the deposition of the former. It appears, however, 

 from the subsequent observations of Professor Sedgwick f , 

 that these appearances are deceptive, and that at the eastern 



* See Mr. Webster's section, Geol. Trans., vol. ii. First Series, plate XI. 



f Anniv. Address to the Geol. Soc., Feb. 1831, p. 9. Professor Sedgwick in- 

 forms me that his observations, made six years ago, have recently been confirmed 

 by Professor Henslow. 



