V. the London and Hampshire Basins. \t 279 



hereafter see to be of the greatest consequence with reference to 

 theories on the origin of the present inequaUties of the earth's 

 surface), more strikingly displayed*/' 



Since the early publication of my ^^ Theory of the Weald De- 

 nudation/' and the explanation there given of the nature and 

 cause of these transverse river-courses_, the subject has become 

 familiar to a great majority of geologists ; all that remains now 

 to be insisted on is the collective view of this phsenomenon : — 

 the watershed diverging by different channels from a common 

 centre, the curious opposition of the river valleys as they traverse 

 the North and South Downs (betokening the original stretch of 

 the deepest rents across the whole breadth of the area), and the 

 uniform character of the whole arrangement^ from the coast at 

 Hastings to the Alton Hills, — all bespeaking a general, simul- 

 taneous, and sudden up burst of the whole. 



Westward from the Alton range, the Meon Valley and the 

 chalk denudation at Winchester maintain the same character of 

 transverse drainage in the courses of the Itchin and the Test. 

 But a change takes place as we approach the extremity of our 

 anticlinal line. The greater part of the Vale of Pewsey, up to 

 the foot of the Marlborough Downs, sheds its waters across the 

 whole breadth of the chalk by the Avon ; and the Vales of War- 

 minster and Wardour send theirs also eastward and southward 

 into the Avon at Salisbury, and so through the New Forest into 

 the Channel at Christchurch. This is still transverse drainage; 

 but it seems to be influenced, if not altogether directed, by the 

 well-known general rise of the secondary strata in a direction 

 N.E. and S.W. all across the kingdom, the line of which elevation 

 passes through that part of Wiltshire. The remarkable trans- 

 verse valleys of the Avon, and of the stream called the Bourne 

 in Mr. Greenough's map — like the winter-bournes of the chalk, 

 very generally dry half the year — seem to answer to this inflec- 

 taon;; !=This requires, and is worthy of further investigation, ru 



" ' In the foregoing sketch I have confined myself chiefly to the 

 phsenomena of elevation and disruption, the basis of the surface- 

 changes we are contemplating. I come now to the third and 

 fourth classes of plia3nomena before spoken of, viz. lacerated 

 escarpments and drift. And as the first two related to upheaval, 

 so the latter have reference mainly to the concomitant action of 

 denuding flood ; — always keeping in mind, that the operations 

 of elevation and denudation have gone hand in hand. 



3. By lacerated escarpments I mean those appearances in the 



Ihih QY^ li'Conybeare and Phillips's Outlines, &c., p. 145. ^^^-oi} a^^l 



