Page:Quarterly Journal of the Geological Society of London, vol. 32.djvu/151

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the present state of Posttertiary geology it is of very great importance (as may be inferred from the Presidential address just published, 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 Rev. D. R. Thomas, in the Journal of the Anthropological Institute (vol. iii. p. 387), and by Mr. W. Boyd Dawkins, F.R.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 introduced, 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 by 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):—