92 D. MACKINTOSH ON THE CEFN AND PONT-NEWYDD CAVE-DEPOSITS. 



1. Coarse sand charged with minute fragments of sea-shells, still found adher- 



ing to one side of a rising branch (ascended by steps) of the Cefn cave *. 

 In the Pont-newydd cave a bed of very fine stoneless clay. 



2. Clay, with angular and subangular fragments of limestone, a few polished 



fragments and pebbles of limestone, likewise a few pebbles of Denbighshire 

 sandstone and grit, felstone, &c. This deposit (which contains bones of a 

 number of tbe usual cave Mammalia) is horizontally continuous with the 

 Upper Boulder-clay of the district (see sequel). 



3. Stalagmitic crust, from less than an inch to 2 feet in thickness. Very little 



now left in the Cefn cave ; apparently absent in the Pont-newydd cave. 



4. Loam, with rounded and smoothed pebbles, bones, teeth, and fragments of 



bone and wood, in the Cefn cave. In the Pont-newydd cave a bed of extra- 

 rounded pebbles, more or less cemented by stalagmitic matter. 



The coarse sand in the uppermost bed (1) in no respect resembles 

 the Upper Boulder- clay on the summit of the plateau above the cave ; 

 it is not what would result from a subaerial rearrangement of the 

 clay ; and the proportional number of fragments of shells is very 

 much greater than that found in the clay f. It is therefore probable 

 that the coarse sand was introduced by the sea through a fissure or 

 fissures in the roof, as Trimmer supposed. 



The clay (2) can be traced along the plain of Lancashire and 

 Cheshire, the coast of Flintshire, and up the vale of Clwyd. It 

 spreads over the gently rising ground between St. Asaph and the 

 Cefn and Pont-newyd caves ; and it may be seen all around the 

 caves, in some places filling up hollows, in others covering plateaux, 

 and in not a few instances clinging to the face of steep slopes, or 

 even adhering to narrow rocky terraces or ledges. I have been 

 familiar with this clay in Cheshire and Flintshire for four years, 

 and have therefore little hesitation in asserting that traces of it, in 

 an unmodified state, may be found at the entrances of both the 

 Pont-newydd and Cefn caves — that in the interior of the Cefn cave, 

 for a considerable distanco from the entrance, there are indications 

 of this clay having once filled the cave nearly, if not quite, to the 

 roof — that in the interior of the Pont-newydd cave it maintains its 

 unmodified character for a considerable distance from the entrance — 

 and that in no part of these two caves has this clay been modified 

 further than what may have resulted from the dropping of calcareous 

 matter, from the temporary ponding back of water in the recesses 

 or hollows, or from accumulation within the caves under condi- 

 tions which may have differed from those without. The angular 

 limestone fragments may have fallen from the roof or sides of the 

 caves during the period of accumulation ; or previously fallen fragments, 

 along with the bones of animals, may have been washed up into the 

 clay by the waves of the Upper-Boulder-clay sea. It ought not to 

 be forgotten that in caves sea-waves are often possessed of very 

 great force, and that they are capable of insinuating themselves into 

 the remotest recesses. 



* I had no difficulty in raking off large quantities with a hammer. It would 

 appear to be present in at least one other branch of the cave. 



t I could see none at all in the clay of the immediate neighbourhood of the 

 cave, though they probably might be found, as I believe Prof. Hughes has col- 

 lected them from the same clay in the Vale of Clwyd. 



