342 Denudation of 



and towards which, the long plains of Gault and 

 Weald Clay directly lead. But this, except with cer- 

 tain rivulets, is so far from being the case, that some 

 streams, like the Beult, rise close to the sea coast and 

 flow westward. If, on the other hand, such a plain 

 as p p once existed, it is easy to understand, how the 

 rivers in old times flowed from a low central 

 watershed to the north and south across the top of the 

 Chalk, at elevations at least as high as, and probably 

 even higher than the present summit-levels of the 

 Downs, 



Then, as by the action of running water, the general 

 level of the inner country was being unequally reduced, 

 so as to form tributary streams each cutting out its 

 own valley, the greater rivers, augmented in volume by 

 these tributaries, were all the while busy cutting and 

 deepening those north and south channels through the 

 Chalk Downs now known as the valleys of the Stour, the 

 Medway, the Dart, the Mole, the Wey, which run athwart 

 the North Downs, and the Arun, the Adur, the Ouse, and 

 the Cuckmare, which, through gaps in the South 

 Downs, flow south. 1 On any other supposition, it is not 

 easy to understand how these channels were formed, 

 unless they were produced by fractures or by marine 

 denudation, of neither of which is there any proof. 

 Through most of these gaps no knoivn faults run of 

 any kind, and the whole line of the Chalk is singularly 

 destitute of fractures. 



We get a strong hint of the probability of the truth 

 of this hypothesis of the denudation of the Weald in 



1 This kind of argument was applied by Mr. Jukes to explain the 

 behaviour of some of the rivers of Ireland, and he supposed that it 

 might possibly apply to the Weald. 'Geological Journal,' 1862, vol. 

 xviii. p. 378. 



