D. MACKINTOSH ON THE CEFN AND PONT-NEWVDD CAVE-DEPOSITS. 91 



11. On the Correlation of the Deposits in Cefn and Pont-newydd 

 Caves with the Drifts of the North-west o/England and Wales. 

 By D. Mackintosh, Esq., F.G.S. (Read June 23, 1875.) 



In the present state of Posttertiary geology it is of very great im- 

 portance (as may be inferred from the Presidential address just pub- 

 lished, May 1875) that some one should attempt to correlate the 

 deposits in caves with the glacial drifts of the neighbourhood. I 

 therefore venture to bring before the Society a brief statement of 

 the results of observations lately made in and around the Cefn and 

 Pont-newydd Caves, Denbighshire. These caves are situated near 

 to each other in the face of a limestone escarpment, on the north 

 bank of the river Elwy. The Pont-newydd cave has been described 

 by Professor M'Kenny Hughes and the Eev. D. R. Thomas, in the 

 Journal of the Anthropological Institute (vol. iii. p. 387), and by 

 Mr. W. Boyd Dawkins, F.B.S., in his work on Cave Hunting. By 

 these writers the cave -deposits are regarded as Postglacial. The 

 best account of Cefn Cave, as it existed before the deposits were 

 nearly all cleared out, is perhaps to be found in Mr. Joshua 

 Trimmer's ' Practical Geology,' published in 1841 *, the following 

 being the order of succession therein stated or implied : — 



1. Sand, silt, and marl, "with sea-shells in one or more places (uppermost). 



2. Loam, with'angular fragments of limestone and bones, filling the cavern 



nearly to the roof {diluvium of old authors). 



3. Crust of stalagmite. 



4. Loam, with smooth pebbles, bones, teeth, and fragments of wood (lowest). 



Mr. Trimmer believed that the lowest of these deposits was intro- 

 duced, before the glacial submergence, by the adjacent river while 

 flowing at a considerably higher level than now. But that the 

 river-channel must then have been excavated to a level as low, 

 if not lower, than at present, is evident from the fact that the 

 Upper Boulder-clay extends down to, and in some places runs 

 under, the river-bed, in a manner showing that here (as elsewhere 

 in the north-west of England and Wales) the river, since the 

 glacial submergence, has been principally occupied in reexcavating 

 its choked-up channel. Trimmer likewise believed that the deposit 

 with sea-shells was introduced by the sea through a fissure in the 

 roof of the cave. 



From the nature and sequence of the deposits in Pont-newydd 

 cave (a considerable portion of which has not yet been cleared out), 

 compared with what I have seen of the remnants still visible in 

 the Cefn cave, and from a further comparison of the facts thus 

 obtained with accounts given b} T Mr. Trimmer, Mr. J. Price, M.A. (of 

 Chester), Professor Hughes, Mr. Boyd Dawkins, &c, I have been 

 led to regard the following as the sequence of the beds (order 

 descending) : — 



* See also paper by Eev. E. Stanley, Proc. Geol. Soe. vol. i. p. 402. 



