i6 2 PREHISTORIC EUROPE. 



supported more extensive snow-fields and glaciers than are now 

 met with in Europe. But as loss occurs in some valleys which 

 do not appear ever to have contained glaciers in their upper 

 reaches, the loss in such cases is believed to be the result simply 

 of melting snow and a heavy rainfall. Mr. Tylor has indeed 

 advanced the view that a Pluvial period accompanied and 

 succeeded the disappearance of great snow-fields and enormous 

 glaciers. Professor Prestwich, as we have seen, conceives the 

 loss to be the result of river-floods commencing at the period of 

 the highest valley-gravels, that is to say at a time when the 

 present valleys were beginning to be excavated, and continuing 

 down to the end of that of the lowest valley-gravel. Mr. Tylor, 

 on the other hand, appears to be of opinion that both the gravels 

 and the loss were laid down by vastly swollen rivers after the 

 valleys had attained very nearly their present depth and breadth, 

 and he would therefore draw no distinction as regards age 

 between the high-level and low-level deposits. It is quite 

 impossible, however, to conceive that any river-floods could 

 have reached the enormous height which such an hypothesis 

 demands. Professor Prestwich may have under-estimated the 

 extent of the ancient floods, and my own observations have led 

 me to believe in the former existence of inundations on a con- 

 siderably more extensive scale than those to which he ascribes 

 the formation of the loams of Northern France and the south of 

 England ; but all the evidence, so far as I am able to read it, 

 appears to bear out his view that the hill-loss and high-level 

 gravels, speaking generally, are of greater antiquity than the 

 valley-loss and low-level gravels. 



The late Mr. Belt advocated a view of the origin of loss 

 which I believe was first suggested by my brother, Professor 

 A. Geikie, who pointed out to Dr. Croll that the excessive 

 accumulation of loss in the Ehine valley may have been due to 

 the presence in the North Sea of a great mer de glace which 

 may have impeded the egress of the rivers to the north and 

 caused them to flood wide regions in the Netherlands. Mr. 

 Belt went farther than this, and maintained the opinion that 



