158 GEOLOGY OF SOME OF THE RIVER-SCENERY OF DERBYSHIRE. 



unyielding, would much more effectually resist the denuding 

 forces of the atmosphere, and only suffer a comparatively narrow 

 gorge to be carved out of it ; or in other words, the denuding 

 agencies of the atmosphere were unable to affect the carboniferous 

 limestone bordering the river in such a manner as to keep pace 

 with the deepening of the river channel. 



Although the surface disintegration of the country at large 

 flanking the river would, as we have seen, proceed at greatly 

 varying rates in different parts of its course, yet the deepening of 

 the river channel itself must have proceeded at the same rate over 

 Yoredale shales and carboniferous limestone alike. The carboni- 

 ferous limestone of Matlock being lower down the stream than 

 the Yoredale shales of Rowsley, the bed of the channel in the 

 latter could only be deepened by its disintegrated materials being 

 carried away down the stream over the river bed at Matlock. 

 The river bed of the Yoredale shales would therefore, so to 

 speak, be compelled to wait for or keep time with the bed of 

 carboniferous limestone lower down in the matter of cutting the 

 channel. 



What has been said with reference to the Derwent at Matlock 

 applies to the Dove at Beresford Hall. The lovely vale known 

 as Dovedale is nothing more or less than a gorge cut in hard 

 and unyielding rocks by the river Dove. Doubless, going back 

 into far antiquity, the soft Yoredale shales which fringe the river 

 prior to its entry into the " dale," and which now lie at a much 

 lower altitude than the top of the carboniferous limestone of 

 Dovedale, were once as high as the latter and have been denuded 

 by atmospheric agencies. 



Perhaps, however, the most striking instance is that of the river 

 Manifold, which, after flowing for a long distance in a low lying 

 Yoredale valley, suddenly breaches a wall of limestone at Apes 

 Tor, near Ecton. The contrast here between the levels of the tracts 

 of country, formed respectively of " Yoredales " and carboniferous 

 limestone, is most marked. 



In the " rough and ready " or " cataclysmal " days of Geology, 

 the theory that all river gorges, such as we have described, were 



