436 



DENUDATION OF THE VALLEY. 



description of the rock moving up hill. This may, however, be explained, by supposing 

 that the phenomenon was seen by persons who fled from the lower grounds, and looked 

 back to the scene of dislocation. The first descent of the disrupted rock might easily 

 escape their notice, whilst its long continued effects in forcing up mounds of the soft 

 earth, against which it was pressing, might, when viewed from beneath, produce the 

 appearance of a rising of the whole mass. 



Denudation of Woolhope Valley. 



To return to ancient phenomena. — The denudation of the valley of Woolhope appears 

 to be the natural result of such an elevation, from a common centre, as we have been 

 considering. Shut out by an encircling ridge from the region of Old Red Sandstone, 

 we should hardly expect to find within its area, any fragments of rock transported from 

 surrounding places, and this is strictly true ; for there is not a trace of boulders or 

 gravel derived from the Malverns or adjacent chains. Insulated, however, as this mass 

 of Silurian rock now is, it must at one period have been covered with the Old Red 

 Sandstone which surrounds it, and through which it has been forced up. Now if this 

 extrusion had been brought about by a succession of small upcasts, we should naturally 

 expect, that some detritus of the overlying strata would be found within the central area ; 

 that some fragments of the Old Red Sandstone and Ludlow rocks would be lodged in the 

 depressions encircling the inner dome. Such, however, is not the case, for the valley is 

 one of clean denudation, there not being within it a fragment of such rocks, any more 

 than debris foreign to itself. When, however, we reflect upon the nature of the 

 elevation, we see in it the inevitable result of the same powerful operations which have 

 produced the form of the valley. For whether we embrace the hypothesis of a 

 sudden expansion or of a number of shocks, we are compelled to call into play the 

 action of currents, both violent and long continued, to explain satisfactorily the great 

 extent of erosion ; and when we see that excavation has proceeded so far, as to groove 

 the broad channels which surround the central dome, and to carry away large portions 

 of the associated rocks, why should we expect to find even a trace of the wreck of over- 

 lying strata, which must have been removed, before the work of denudation could com- 

 mence upon the inferior deposits ? 



If, however, no detritus be observable within the valley, we no sooner issue from it at 

 Mordiford, where the only gorge of magnitude opens into the low country, than we meet 

 with accumulations of conglomerate and gravel. These materials have all been derived 

 from rocks belonging to the valley, including finely comminuted materials of the Old 

 Red Sandstone. Such accumulations are cut through to a considerable depth in the 

 road from Mordiford to Fownhope, and are spread out near the mouth of the gorge. 

 In like manner, similar detritus is lodged upon the external slope of the elevated tract, 

 frequently obscuring the junction of the Upper Ludlow rock with the Old Red Sandstone. 



