Mr Stanle3^'s Memoir on a Cave at Cefn in Denbigshire, 49 



of man convulsions on record capable of producing effects in- 

 finitely more stupendous than those required for the compara- 

 tively insignificant purpose of the case before us. 



Let us suppose, then, that at a certain time some great con- 

 vulsion occurred (as the bursting of a lake, violent rains or 

 waterspouts) causing an irruption of waters far exceeding the 

 last, so copious as to raise the level of the descending stream 

 some feet higher than the caves, and at the same time impreg- 

 nate it with those fine particles of loamy mud which we find 

 deposited in the cave. In fact, a catastrophe, similar to that of 

 modern date, which occurred near St Liicido in Calabria, when 

 the ground is described as having been dissolved, so that large tor- 

 rents of mud inundated all the low grounds like lava, the swampy 

 soil in two ravines being filled with calcareous matter. We 

 may conceive this moving mass acting with inconceivable pres- 

 sure on the rocky limestone barrier between it and the plains 

 below, till at length forcing a passage through some weaker part, 

 its concentrating volume burst forth with inconceivable violence, 

 and finally tore up every opposing obstacle. Such was the effect 

 of the pressure of water on a barrier something similar in the val- 

 ley de Hagne in Switzerland, which I had an opportunity of in- 

 specting a few days after the catastrophe, productive of such dis- 

 astrous effects for upwards of twenty miles below ; and when we 

 bear in mind that limestone ranges are frequently honey-comb- 

 ed, if I may so speak, with fissures and chasms connected with 

 cavernous chambers within, instances of which occur in the very 

 rocks adjacent to the caves before as * ; we are not making sup- 

 positions unsupported by facts. The consequence of this irrup- 

 tion would naturally be, not only the probable removal of the 

 rocky barrier, but, by powerful erosion, the excavation of the 

 bed of the valley itself, till it had scooped out its course to the 

 level at which it now runs. Whether such an inundation of 

 mud and diluvial detritus in its progress towards die sea may 

 have caused the wide extent of low alluvial land, forming what 

 is now called Rhyddlan Marsh, may be matter for future inquiry ; 



• At the base of the cliff of Galltfaenan, a stream gushes out from a sub- 

 terraneous channel, through which it is supposed to be conveyed from a con- 

 siderable distance. 



VOL. XIV. NO. XXVII. JANUARY 1833. D 



