94 D. MACKINTOSH ON THE CEEN AND PONT-NEWYDD CAVE-DEPOSITS. 



glaciated stones and a few boulders), which is qnite as persistent as 

 the sand and gravel, but which has not yet been clearly traced to a 

 height of more than a few hundred feet above the present sea-level. 

 The first indicates a cold period, the second a comparatively mild 

 period, and the third, I believe, a second cold period, though this 

 has been disputed by Professor Hughes and Mr. Kinahan. Believing 

 with Professor Eamsay that the great glacial submergence com- 

 menced before the ice-sheet or ice-sheets disappeared from the 

 country, that the lower Boulder-clay (so far as it is of marine 

 origin) was accumulated while the land was sinking, and that the 

 sand and gravel formation was deposited while the land was rising — 

 and likewise believing in an interglacial period, during the first part 

 of which the land was still submerged, dry land prevailing during 

 the second part, it follows that there must have been a second sub- 

 mergence, during which the upper Boulder-clay was deposited. It 

 is possible that the pebble-bed in the Pont-newydd cave may have 

 been deposited as the land was rising out of the interglacial or 

 Middle- Sand-and-gravcl sea, and that pebbles and loam may then 

 have been introduced into the Cefn cave ; but as the neighbourhood 

 could not have been inhabited by land animals until after the 

 emergence of the land, the bones, teeth, and fragments of wood 

 which were found associated with the lowest deposit in the Cefn 

 cave may have been washed in by rain through fissures in the roof. 

 After the accumulation of the stalagmite, more bones must have 

 been introduced, and the cave may have been temporarily inhabited 

 by the hyaena. This state of things may have been brought to a 

 close by the submergence of the cave beneath the waters of the 

 Upper-Boulder-clay sea, which filled the cave nearly (if not, in many 

 places, quite) to the roof. The sand with sea-shells may have been 

 introduced through fissures in the roof while the plateau above the 

 cave was gradually rising above the sea-level. 



The above imperfect explanation is the best I can offer concerning 

 the mode in which the different and very dissimilar deposits in the 

 Cefn and Pont-newydd caves were accumulated. 



P.S. — As may be learned from his paper read before the Anthro- 

 pological Institute, Professor Hughes found Palaeolithic flint imple- 

 ments and a human tooth, which he believed came from the bed I 

 have called Upper Boulder-clay, in the Pont-newydd cave*. 



* Since this paper was written, Professor Hughes has found a large frag- 

 ment of felstone in the lowest bed of the Pont-newydd cave. 



