Yol. 54.] ANNIVERSARY ADDRESS OF THE PRESIDENT. xci 



formed when the streams that flow down near Llysmeirohion ran at 

 a greatly higher level, the intermediate ground being all filled np 

 with drift, or perhaps when the drift choked np the Elwy Valley, 

 as we have seen above was once the case, some of its waters may 

 have found their way into the limestone-rocks above Plas Heaton.' 

 Again he says, ' More probably some, if not all, of the Cefn Caves 

 were formed much later, when the gorge was filled with Boulder 

 Clay, and the water ran into swallow-holes along the margin of the 

 drift and rock, and part of such an one became a sloping cave. In 

 the submergence, this cave cannot have been formed, as nothing 

 would make the current fall to open out vertical passages at the 

 bottom of the sea.' 



When the evidence of the earlier explorers of the Cefn Caves (the 

 Eev. E. Stanley and Mr. Joshua Trimmer) is examined, it becomes at 

 once clear that the main Cefn Cavern must have been formed (as 

 was probably the case with most of the others to which I have re- 

 ferred) at a much earlier period than that suggested by Prof. Hughes. 

 Mr. Trimmer says^ : — 'It communicates with the surface by fissures, 

 and has an entrance from the face of the cliff, about 100 feet 

 above the river, and 200 above the sea. The lowest parts yet 

 examined are about 10 feet high, and are filled very nearly to the 

 roof with sedimentary deposits, containing bones and teeth of the 

 hyaena, bear, and rhinoceros. These are found in two strata, 

 separated by a crust of stalagmite. The lowest is below the level 

 of the entrance from the face of the cliff, and contains bones and 

 teeth, enveloped in sediment and mixed with smooth pebbles, like 

 those of the adjacent river, and with fragments of wood. It is 

 covered by a crust of stalagmite, and above that the cave is filled 

 nearly to the roof with calcareous loam, containing bones and 

 angular fragments of limestone, on the surface of which are sand 

 and marl containing fragments of marine-shells, like those dispersed 

 over the neighbouring district. The sediment within the cave is 

 generally finely laminated. This cavern has been compared, as we 

 have already observed, to that of San Ciro ; but they differ in these 

 important particulars, that in the Cefn Cave there are no lithodomous 

 perforations in the limestone, that the marine remains are confined 

 to the upper part, and that the lower deposit of pebbles and bones 

 is covered by a crust of stalagmite. This last fact, whether the 

 cave was or was not a den of hyaenas, proves that it was subaerial 



1 * Geology & Mineralogy,' London, 1841, p. 400. 



