50 Mr Stanley's Memoir on a Cave at Cefn in Denbigshire. 



at all events, local appearances render such a conjecture by no 

 means improbabla On the final erosion of the former bed of 

 the river now running at the bottom oi' a still deeper valley, the 

 present upper caves would thus be left high on the fa9ade of 

 the cliffs as we now behold them. It may be argued, that, on 

 the retreat of the waters, the mud injected into the recesses of 

 the cave would have been removed. But two reasons may be 

 urged why this should not have happened : 1*/, That in conse- 

 quence of the very peculiar character of the earthy particles, the 

 laminous sediment would have been deposited in a few hours in 

 so compact and adhesive a state, as to defy any ordinary means 

 for its removal. The particles are indeed so extremely fine, and 

 impalpable and unctuous, that it is almost impossible to separate 

 them sufficiently for the purpose of microscopic observation. 

 Consequently when, in addition to this, the adhesive character of 

 such loamy argillaceous atoms is taken into consideration, it 

 may be well conceived that a very compact deposit is easily 

 formed. So minute indeed are the particles, that 20 grains in 

 two ounces of water, gave the liquid as deep an ochrey colour as a 

 mixture of the liquid and the powder in equal parts, with all 

 the appearance at the same time of being in a state of chemical 

 solution. In two or three hours, however, they subsided, leaving 

 the water nearly colourless, and this, when poured off, left the 

 deposit in the form of a strong adhesive paste. Very few hours, 

 therefore, and still more, if we allow a duration of days, would 

 have effectually choked up the interior of the cave with the 

 compact mass now existing, more particularly, when we further 

 take into consideration that the water admitted within the reces- 

 ses would have been in a state of comparative quiescence and stag- 

 nation, little if at all affected by the agitation of the external 

 stream. 2f%, On reference to the ground- plan. Fig. 1, PI. II., 

 it will be perceived that whereas the course of the river is at the 

 cave from about N. to S., the portion of the cave entirely blocked 

 up commenced at the north-east corner of the great opening, 

 about 20 feet within, and that its course is to the northward ; so 

 that the descending waters would naturally be drained gradually 

 from the injected mud, by no means acting upon it as a disturb- 

 ing force, probably, moreover, forcing its way and clearing 

 out an upward channel by pressure through the orifices before 



