PLEISTOCENE RIVER-DEPOSITS, 135 



severe to cover the rivers with a thick coating of ice without 

 having its habits profoundly modified ; and such an alteration 

 of habits would certainly leave its mark in other modifications 

 in the fossil skeleton than those minute differences which have 

 been observed when it has been compared with that of the 

 living Hippopotamus amphibius." 1 The occurrence of remains 

 of the cave-haunting bears, lions, and hyaenas, and of the bison 

 and other herbivores, is further indicative of a climate capable of 

 nourishing vegetation sufficiently abundant to sustain the herds 

 of oxen, deer, and other animals upon which the great car- 

 nivora preyed. And the truth of this inference is greatly 

 strengthened, and even as it seems to me entirely confirmed, by 

 the facts already set forth in regard to the land-plants and mol- 

 lusca which have left their remains in such deposits as that of 

 La Celle, which clearly belongs to the ancient Pleistocene 

 accumulations of the Seine valley, overlying as it does the so- 

 called diluvium gris, or gray gravel, and belonging, according to 

 M. Tournouer, to a late stage of the Pleistocene Period. In 

 short, the evidence supplied by the old " river-drifts " — those of 

 high and low level alike — is of precisely the same character as 

 that of the caves. It speaks to us of alternations of mild or 

 genial and cold climatic conditions. If the evidence of a cold 

 climate seems to predominate, it is only what we might have 

 expected. It was during the continuance of such a climate 

 that the rivers would be most energetic, ploughing into the 

 rocks through which they flowed, and pushing enormous quan- 

 tities of detritus down their valleys. As each spring returned, 

 wide tracts of country would be inundated, and many animals 

 might be drowned, and their disjointed skeletons eventually 

 come to be entombed in silt and sand. In like manner such 

 loose bones or other waifs as lay bleaching on the ground 

 would often be swept away, with other ddbris, by the floods. 

 For floods and inundations are the rule in all countries which 

 are subject to severe winter cold ; whereas they are the excep- 

 tion in genial temperate climates. Hence the river-deposits of 



1 Cave-hunting, p. 374. 



