H4 ORIGIN OF SCENERY OF BRITAIN 



directly by bringing hard and soft rocks against each 

 other. 



In Britain, as in other countries, there is a remark- 

 able absence of coincidence between the main drainage 

 system and the geological structure of the region. We 

 may infer from this fact either that the general surface, 

 before the establishment of the present drainage system, 

 had been reduced to a base-level of denudation above or 

 under the sea, the original inequalities of configuration 

 having been planed off irrespective of structure ; or 

 at least, that the present visible rocks were buried 

 under a mass of later unconformable and approximately 

 level strata, on the unequally upraised surface of which 

 the present drainage system began to be traced. Where 

 the existing watershed coincides generally with the 

 crest of an anticline, its position has obviously been 

 fixed by the form of the ground produced by the 

 plication, though occasionally an anticline may have 

 been deeply buried below later rocks, the subsequent 

 folding of which along the same line would renew 

 the watershed along its previous trend. Where drain- 

 age lines coincide with structure, they are probably, 

 with few exceptions, of secondary origin ; that is, they 

 have been developed during the gradual denudation 

 of the country. Since the existing watershed and main 

 drainage-lines of Britain are so independent of struc- 

 ture, and have been determined chiefly by the configu- 

 ration of the surface when once more brought up 

 within the influence of erosion, it may be possible 

 to restore in some degree the general distribution of 

 topography when they were begun. 



One of the most curious aspects of the denudation 



