Page:Quarterly Journal of the Geological Society of London, vol. 32.djvu/152

92 1. Coarse sand charged with minute fragments of sea-shells, still found adhering 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 the 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. 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 distance 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 conditions 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.