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RIVER- GORGES IN CORNWALL AND DEVON. 



67 



deep, their existence would not be suspected if the plain were viewed 

 from a distance ; for then it appears simply as a wide expanse of 

 level fields and waste land. The area is divided by these streams 

 into flat-topped blocks of land, where no rock is exposed at the 

 surface, separated one from the other by rocky chasms. 



These five valleys exemplify the several stages in the development 

 of gorges, and, when seen from the sea, the degree to which they 

 have been cut down by their streams obviously ranges from the 

 coastal waterfall to a valley accordant with the sea at low tide. 

 Moreover, they possess similar features which characterize them as 

 a group, and differentiate them from the valleys of the country 

 adjoining them on the south. These features are the waterfalls, 

 the cascades and rapids, the potholes, and the bare craggy rocks 

 seaming their slopes. 



The first valley in this district, known as Pentargon, is short, 

 and marks an early stage in the development of a gorge ; while its 

 stream forms a waterfall over the. edge of the cliff. It has cut a 

 sharp gorge in the Carboniferous grits and shales, but this does 

 not extend far inland. 



The Valency Valley. 



A little farther south is the deep and important valley through 

 which the Valency flows swiftly to the sea. It has sides which 

 are precipitous, with overhanging rocky crags and bluffs, and 

 to it the name gorge well applies. The stream has cut a channel 

 which is swamped at its mouth by the sea at high tide, and forms 

 the little harbour of Boscastle. The valley is of great beauty and 

 in places approaches even to grandeur, especially near the sea, 

 where precipices of sharply-folded beds of grit, veined with threads 

 of white quartz, are undercut by the waves. 



The country, however, between Boscastle and the Rocky Valley 

 is dull and commonplace, except for the magnificent range of cliffs 

 that bounds it; but it enhances the beauty of the next gorge 

 by forming a foil to its mixture of rocks and woodland. 



The Rocky Valley. 



This gorge owes its origin to the cutting power of what was 

 originally a coastal waterfall, but has how retreated inland for a 

 distance of several miles, leaving numerous evidences of its activity 

 in the walls of the chasm. It commenced its work when the land 

 was uplifted in post-Pliocene times, by cutting a deep gorge into 

 the plateau, and has since continued ripping its way backwards 

 and down wards through the bare rock until it has breached the old 

 cliff -line bounding the plateau. This work has been effected by 

 the formation of a series of large hollows or potholes one below 

 the other, many of which remain in the walls of the gorge ; and to 

 this agency I ascribe the formation — at any rate, in part — of all 

 the gorges of the West of England, for similar phenomena are 

 visible at different places in these gorges. 



