RELICS OF MAN IN THE GLACIAL PERIOD. 273 



covered by marine sands and by an upper boulder-clay, 

 identical in character with that found at many points in 

 the Vale of Clwyd. The paleontological evidence sug- 

 gests that the deposits in question are not preglacial, but 

 may be equivalent to the Pleistocene deposits of our river- 

 valleys."* 



If the views of Professor Lewis and Mr. Kendall are 

 correct concerning the unity of the Glacial period in Eng- 

 land, the shelly and sandy deposits connected with these 

 Clwydian caves at an elevation of 400 feet or more would 

 be explained in connection with the marginal lakes which 

 must have occupied the valley during both the advance 

 and the retreat of the ice-front ; the shells having been 

 carried up from the sea-bottom by the ice-movement, after 

 the manner supposed in the case of those at Macclesfield 

 and Moel Tryfaen. If, therefore, the statements concern- 

 ing the discovery of flint implements in this Cae Gwyn 

 cave can be relied upon, this is the most direct evidence 

 yet obtained in Europe of man's occupation of the island 

 during the continuance of the Glacial period. 



In all these caves it is to be noted that there is a sliarp 

 line of demarcation between the strata containing palaeo- 

 lithic implements and those containing only the remains 

 of modern animals. Palaeolithic implements are confined 

 to the lower strata, which in some of the caves are sepa- 

 rated from the upper by a continuous bed of stalagmite, 

 to which reference will be made when discussing the 

 chronology of the Glacial period. The remains of ex- 

 tinct animals also are confined to the lower beds. 



The caves which we have been considering in England 

 are all in limestone strata, and have been formed by 

 streams of water which have enlarged some natural fis- 

 sures both by mechanical action in wearing away the 

 rocks, and by chemical action in dissolving them. 



* H. B. Woodward's Geology of England and Wales, pp. 543, 544 



