46 Stanley's Memoir on a Cave at Ce/h in Denhigshire. 



more experienced and professed geologists than myself, may turn 

 their attention to its peculiar features, the consideration of which 

 may possibly throw additional light on these singular and inter- 

 esting museums which have been handed down to us, unheeded 

 or undiscovered by our forefathers, and the old times before 

 them. 



In the first place, then, I should suggest the probability, that 

 a barrier, to a certain extent, must have existed, connecting the 

 approximating headlands of Cefn and Galltfaenan, from the 

 appearance of the valley, indicating a wider spread of water 

 permanently flowing through it than could ever under any cir- 

 cumstances occur at present. The bed of this valley, when seen 

 from the heights of Galltfaenan, shews an ample expanse of 

 nearly flat meadow land for a considerable distance up the vale, 

 as if snK)othed down by the operations of a body of deeper wa- 

 ter, the lower current of which would act with less erosive power 

 than the turbulent bed of a wide and shallow mountain torrent. 

 From a closer inspection, however, it appears far from impro- 

 bable, that a much more formidable barrier might have existed, 

 by a natural union between the cliifs of Cefn and Galltfaenan, 

 similar in character, form, and structure. No large fragments, 

 to justify such a supposition, are, I am aware, to be found 

 close at hand, or even on the lower levels between these cliff's 

 and the sea. But to those who are conversant with the in- 

 calculable power of agitated water as a moving force, even in 

 projecting huge blocks up steep acclivities, it is unnecessary to 

 dwell upon the probability that the wreck of this barrier once 

 broken, however gigantic might have been its ruins, was hurried 

 downwards with a rapid comminution of its materials, till thev 

 reached the deeper beds of the ocean. In support of this view, 

 I shall merely mention as an instance of the irresistible force of 

 currents, a fact mentioned by Dr Hibbert in his account of the 

 Shetland Islands, p. 5S7, and quoted by the learned Secretary 

 to this Society, in his valuable work on the Principles of Geology, 

 vol. i. p. 259. In the winter of 1802, a tabular-shaped mass, 

 weighing between 15 and 20 tons, was not only torn up from its 

 original bed, but removed to a distance from 80 to 90 feet. 

 Another in 1818, of still larger dimensions, was upheaved from 

 its bed, and borne to a distance of 30 feet, where it was shiver- 



