THE CHEESEWRING, CORNWALL, AND ITS TEACHINGS. 147 



surface of the sea ; and, as, I have said, there are frequent 

 examples of these once-submerged plains, as, for instance, in 

 Cardiganshire, of which the accompanying figure taken from 

 Sir A. C. Eamsay's work is a representation (Fig. 3). What 



i§. A J ). £ V £ i "* ^ * 



FIG. 3. — SECTION TO ILLUSTRATE STRUCTURE OF A PLAIN OF 

 MARINE DENUDATION. 



Geceralized Section across the Silurian Strata of Cai-diganshire (after Kamsay). 

 Phys. Geo. and Geog. of Great Britain, 5 Edit., 'p. 497. 



is specially remarkable is the fact that the plains are quite 

 independent of the nature and position of the rocks ; they are 

 carried across hard rocks and soft, highly inclined or contorted 

 as well as nearly horizontal strata ; though of course the 

 harder rocks have withstood the marine action better than the 

 softer. Thus in the valley of the Avon at Bristol we see the 

 solid beds of Carboniferous limestone rising in succession from 

 below each other, but terminating abruptly at the sky-line in a 

 flat surface or plateau, through which the river-valley has 

 been eroded by the action of the river itself in the course of 

 ages. The Carboniferous, Devonian, and Silurian formations of 

 South Wales, generally highly inclined, terminate along a nearly 

 level sky-line as seen from the Gorge of the Avon to the 

 north. Further to the east we have the remarkable table-land 

 of the Cotteswold Hills of Gloucester and Somerset, breaking 

 off towards the west in an elevated escarpment rising above the 

 vale of the Severn. Finally, when we come to Cornwall itself, 

 the subject of more immediate interest, we find that the 

 surface of the country resolves itself into a gently sloping table- 

 land commencing in the coast cliffs, penetrated by numerous 

 valleys descending into the sea, and composed of various 

 strata of Carboniferous or Devonian age, which have been highly 

 tilted, or thrown into numerous folds and flexures, but which 

 break off along the sky-line, the once continuous portions having 

 been as completely swept away as if they had never existed. 

 Hut we have only to attempt to restore the vanished strata 

 along the lines of dip and flexure to become convinced that 

 thousands of feet have been denuded from off the existing 

 surface of the country. 



It is clear from what has been said that this erosive action 

 has been effected by some agent acting horizontally, breaking 

 down and carrying away the materials which once overspread 



