CONSEQUENCES OF MARINE DENUDATION. 397 



later attack will be spread off-shore on the platform abraded in the earlier 

 attack. The basal strata of the unconformable cover thus formed must 

 indicate their marine origin and must be appropriately related in com- 

 position and texture to their sources of supply. The drainage systems 

 of the land will be essentially extinguished by the encroaching sea. 

 When the region rises, with the cover of new sediments lying evenly on 

 its smoothed back, a new system of original consequent streams will take 

 their way across it. If the elevation be sufficient, the streams will in- 

 cise their valleys through the cover of new sediments and in time find 

 themselves superposed on the " oldland " beneath. As time passes, 

 more and more of the cover will be stripped off; at last it may disap- 

 pear far and wide, although the stripped surface of the oldland may still 

 retain a generally even sky-line as a memorial of its once even denuda- 

 tion. Now, in this case, the rivers by which the dissected plateau is 

 drained will have at most only a very slight adjustment to its structure. 

 Their courses will have been inherited from the slope of the lost cover ; 

 they will at first run at random across hard and soft structures ; a little 

 later some adjustment to the discovered structures will be made, but as 

 long as the even sky-line of the upland is recognizable, only the incom- 

 plete adjustments appropriate to the adolescent stage of denudation can 

 be gained. 



Examples of dissected Uplands with adjusted Drainage. 



This essay has already reached so much more than its expected length 

 that it will not be possible to give extended space to the consideration of 

 specific examples. This is, however, no great disadvantage, inasmuch as 

 the number of exam})les in which the problem has been considered in 

 relation to drainage arrangement and otlier discriminating features is 

 very small. The various articles already referred to concerning the geo- 

 graphical development of the Appalachian region treat this aspect of the 

 subject with some care; to these may be added my paper on " Certain 

 English rivers," in which it seems to me that there is shown some ground 

 for the consideration of the- alternative to the usual English view. Of 

 the Ardennes it may be briefl}^ said that systematic longitudinal and 

 transverse streams are well developed in certain areas, and in those parts, 

 at least, there does not appear direct evidence of marine transgression. 

 (Sheets 48 and 54 of the Belgian topographical map (scale, 1 : 40,000) ex- 

 hibit these features very clearly. On the other hand, the branches of the 

 Rhine and the Moselle in the Schiefergebirge suggest superposition from 

 a lost cover, as mapped on the sheets of the Karte des Deutschen Reichs 

 (scale, 1 : 100,000). 



It is manifest that many plains of denudation, now uplifted and more 



