DRIFTS OF THE YALE OF CLWYD. 



Ill 



Quart. Journ. Geol. Soc. vol. xxiii. p. 108, vol. xxiv. p. 515, vol. xxv. 

 p. 213, vol. xxviii. 1872, p. 410 ; Searles Wood, Quart. Journ. 

 Geol. Soc. vol. xxiii. p. 391, Geol. Msls. vol. iii. pp. 57, 99, 348, 

 398, vol. ix. 1872.) 



If, then, the drift that hangs upon the slopes above Flynnon Beuno 

 and chokes the mouth of the caves must be later than the emergence 

 which left the Talargoch gravels, what can it be '? It is not a 

 river-deposit. If the Yale of Clwyd was ever filled from side to 

 side up to that level by the old western drift, that drift was cleared 

 out during the submergence, and there is no reason for believing 

 that the valley was ever so filled again. Thus there was nothing 

 for rivers to have run upon at that high level. Its character and 



fig. 5. — View of Old Fence, Ffynnon Beuno. 



arrangement also prove that it is not alluvium or the torrent-debris 

 of the ravine. 



In the Plas Heaton cave the mass of drift overlying the north end 

 of the cave is very like the upper St. Asaph Drift, and is probably 

 derived directly from it ; but in the case of Cae Gwyn cave I do 

 not think this is the case. The material that I saw in the section 

 close to the rock where the earth had fallen in did not appear to 

 me to resemble any known section in the undisturbed St. Asaph 

 Drift. It is quite unlike the great masses of red sand exposed here 



