498 Plains of Marine Denudation. 



that the result would be an inclined plane like that of 

 the straight line b b in the diagram. Let South 

 Wales be such a country: then when that country 

 was again raised out of the water, the streams made 

 by its drainage immediately began to scoop out 

 valleys; and though some inequalities of contour 

 forming mere bays may have been begun by marine 

 denudation during emergence, yet in the main I believe 

 that the inequalities below the line b b have been 

 made by the influence of rain and running water. 

 Hence the number of deep valleys, many of them steep- 

 sided, that diversify Wales, all the way from the Towey 

 in Caermarthenshire to the slaty hills near the southern 

 flanks of Cader Idris and the Arans. 



On ascending to the upper heights, indeed, anywhere 

 between the Vale of Towey and Cardigan Bay, it is 

 impossible not to be struck with the average uni- 

 formity of elevation of the flat-topped hills that form 

 a principal feature of the country. The country already 

 described as seen from Kamsey Island is part of this 

 plain, 1 and much further north let anyone ascend Aran 

 Mowddy or Cader Idris in Merionethshire, and look 

 south and south-east. From thence he will behold, as far 

 as the eye can reach, a wide extent of flat-topped hills, 

 which form the relics of a vast tableland, now inter- 

 sected by numerous rivers, which, in the long lapse of 

 untold ages, have scooped out unnumbered labyrinthine 

 valleys eastward into Montgomeryshire, and far south 

 into Cardiganshire. Between the rivers Towey and Teifi, 

 and in other areas, these hills, in fact, form the relics of 

 a great plain or tableland in which the valleys have been 

 scooped out ; and in the case of the country repre- 

 sented in fig. 97, ' the higher land, as it now exists, is 

 1 See p. 487 



