602 SCIENCE PROGRESS 



ment enclosing the Weald, there are, on the contrary, long 

 peninsulas and island outliers of chalk ; while the crest line 

 follows a very sinuous course. 



The reason for this disparity is this. In the Weald the 

 absence of spurs and outliers of chalk is an indication that 

 there was higher ground from which the streams descended, 

 making frontal attacks on the chalk and spreading east and 

 west until they found suitable exits, which have resolved into 

 the main arteries of the present day. 



Such a history certainly goes to explain this uniformity 

 and absence of outliers, while it clearly indicates how the main 

 valleys — so often quoted as presenting a geological difficulty — 

 have been formed. This question of these river-valleys is dealt 

 with below. 



Starting with this presumption, one cannot fail to be struck 

 with the difference in outline and aspect of the Dorset- Wilts 

 chalk frontier, which speaks eloquently of an immunity from 

 sub-aerial erosion possessed by the chalk summits, as com- 

 pared with the Greensand and Kimmeridge clay flanking it. 



Here it is evident that the erosion of formations adjacent 

 to the chalk started at a fairly even level with the chalk. 

 The same differential erosion was in operation ; but rivers, 

 only under a mild compulsion of gravity, constantly shifted 

 their beds, enlarging a bay here, and leaving peninsulas and 

 islands there, to follow the usual meandering habits of low- 

 land water systems. 



It is perhaps because, under such conditions, the leaving 

 of outliers would be inevitable, that investigators have been 

 hitherto misled as to the cause of the Weald denudation, and 

 have been induced to infer that some other factor of a more 

 sweeping character was responsible for the regular line of 

 escarpment. 



The Transverse Valleys 



In Our opinion the various causes of the denudation of the 

 Weald are still to be sought, and the question may still be con- 

 sidered an open one. Especially do we think this to be the case 

 when considering the point on which the whole of the question 

 seems to turn, viz. : how to account for the gaps cut in the chalk 

 escarpment to the north and the south. — F. R. Bennett, late of 

 the Geological Survey, in Ightham : the Story of a Kentish 

 Village " (The Homeland Association). 



