Mackintosh — The Sea v. Bain and Frost, 65 



it is difficult to conceive of rain or frost originating a cliff. But 

 suppose these agents to have succeded in originating a cliff, they 

 could not cause it to recede to any extent, because, in time, the fall of 

 debris would put a stop to their progress, by accumulating so as to 

 protect the under bed from farther decay. In the absence of a 

 river to remove the talus, the cliff would become a slope. If, as the 

 subaerialists admit, rivers are incapable of maintaining the vertical 

 walls of their channels without a continual removal of the debris, 

 how can rain, frost, or even springs, wear back an escarpment in the 

 absence of an agent of sufficient power to carry away the fallen 

 fragments or blocks. 



It is not true that rain and frost are possessed of a regular or 

 systematic undermining power. Suppose a soft and yielding bed 

 under a hard stratum of rock. By the time the former is worn 

 backwards so as to cause the latter to project, it ceases to be acces- 

 sible to rain (and, in the absence of springs, to frost), unless it be. 

 situated on the windward side of a declivity. "With regard to frost, , 

 it seems to be forgotten that it would be less likely to influence claj^ 

 or shale than the overlying jointed sandstone or limestone rock... 

 The subaerialists would likewise appear to forget that there are> 

 many cliffs and escarpments the bases of which do not consist of. 

 comparatively yielding materials.^ 



But one of the most striking proofs of the inadequacy of atmo- 

 spheric action to originate or alter the configuration of cliffs is to 

 be found in the fact that many lines of cliff in limestone districts 

 present little or no debris along their bases. Some of them appear as 

 if the agent by which they were formed had swept away nearly all 

 the traces of its undermining action, while under other cliffs we find 

 deposits consisting of matter which could not have been derived 

 from the rock above. Among the limestone cliffs, which present 

 few indications of atmospheric waste, may be mentioned the more 

 compact and mural cliffs of the Mendip Hills, in Somersetshire ; of 

 Derbyshire, especially near Matlock ; of the Eglwyseg range, especially 

 the upper terraces, near Llangollen ; of the neighbourhood of Aber- 

 gele and Cefn, North Wales ; and of many parts of Craven, in 

 Yorkshire. 



Marine Debris under Cliffs — I believe that in most instances an 

 attentive examination would show that the majority of the blocks 

 and fragments found scattered under cliffs have not fallen since the 

 last emergence of the land. They either exist in too great numbers, 

 at too great a distance from the parent cliff, heaped vip, apparently 

 thrown back, or arranged in such a manner as to point to the 

 laterally-operating and revulsive action of the sea. At Wliarncliffe, 

 near Sheffield, and other parts of the West-Eiding of Yorkshire, we 

 may see the neighbourhood of Millstone -grit escarpments strewn 

 with blocks, both angular and rounded, some of them isolated and at 

 a considerable distance from any cliff, while others are arranged in 



• The chalk escarpments above the terraces of upper greensand, in "West Sussex, 

 Hampshire, etc., furnish striking examples of the effects of an tmconditional under- 

 mining agent. 



VOL. ITI. — NO. XX. 5 



