THE TUNDRAS AND STEPPES OF PREHISTORIC EUROPE. 343 



gravel terrace (that of the third glacial epoch) is in like manner sheeted 

 in loss. The loss on these three separate horizons is for the most part 

 wind blown, and exactly resembles that of middle Europe generally, 

 showing the same structure and arrangement, and containing a similar 

 assemblage of organic remains. 



To what extent each of these "horizons" of loss may be represented 

 in the low grounds of middle Europe we can not definitely say. But as 

 the materials of the loss are for the most part of fluvio-glacial origin, it 

 is obvious that such accumulations must have been formed during each 

 successive advance of the alpine glaciers. As each glacial epoch passed 

 away those accumulations were greatly modified by the wind, and drifted 

 into the valleys that drain the Alps, where they were subsequently 

 covered and to some extent preserved under the morainic and tluvio- 

 glacial deposits of the succeeding epoch of glacial advance. It seems 

 probable, therefore, that the wind-blown loss of the low grounds of 

 middle Europe does not belong exclusively to any one particular stage 

 of the glacial period. It is impossible, however, at present to divide 

 it up into separate stages. But we may feel sure that if tundra and 

 steppe faunas succeeded each other again and again in the valley of 

 the Ehine, they could hardly fail to have done the same in the wide 

 plains of middle Europe. 



It will be remembered that at the Schweizersbild the deposits con- 

 taining remains of tundra and steppe faunas rest immediately upon 

 fluvio-glacial gravels. These gravels were laid down during the third 

 glacial epoch. It is quite certain, therefore, that the faunas referred to 

 must have entered Switzerland after the retreat of the glaciers from the 

 low grounds. But how long an interval may have elapsed between the 

 disappearance of the glaciers and the advent of the lemmings and 

 their congeners we can not tell. All we know is that after the appear- 

 ance of the tundra fauna in Switzerland the climate, at first cold and 

 arctic, gradually became less extreme, so that in time a steppe fauna, 

 and afterwards a forest fauna, succeeded. In other words, no percepti- 

 ble hiatus separates the present from the conditions that obtained when 

 the reindeer hunter vanished from the alpine lands. He was succeeded 

 by Neolithic man, just as the latter was followed by the men who used 

 bronze and iron implements and tools. So far as the evidence of the 

 Schweizersbild rock shelter is concerned, we should infer that no great 

 alternations of cold and genial epochs followed after the final retreat of 

 the great glaciers of the third glacial epoch. But, as we shall see 

 presently, the tale told by that interesting rock shelter is incomplete. 

 Certain considerable climatic changes did take place after the third 

 glacial epoch had passed away. The evidence of such change, however, 

 though not wanting in the alpine lands, is much more clearly displayed 

 in northwestern Europe. To the testimony yielded by the glacial and 

 interglacial deposits of that region, therefore, we shall now direct 

 attention. 



