346 THE TUNDRAS AND STEPPES OF PREHISTORIC EUROPE. 



Later climatic oscillations followed, but ou a decidedly reduced scale. 

 The effect of these was, naturally enough, most marked in northwestern 

 Europe, decreasing gradually southward, and doubtless eventually 

 fading away in the lower latitudes of the continent. It is not neces- 

 sary for my present purpose to do more than briefly indicate the gen- 

 eral character of these later changes so far as they affected our own 

 area. 



The local glaciers of the British mountains, some of which, as I have 

 said, actually entered the sea, at last began to retreat. The climate 

 became more genial, and so once more favored the growth of forests, 

 which in many places began to overspread the now dry peat bogs, 

 beneath which the trees of the earlier forest epoch lay entombed. 

 Eventually, however, colder and more humid conditions returned, and 

 small glaciers appeared iu a few places among the loftiest heights of 

 the Scottish Highlands. The position of the moraines of these glaciers 

 indicates a height of 3,500 feet for the snow line. The forests now, as 

 before, began to decay in many places, and the bog moss and its allies 

 again extended in all directions, and so, eventually, a second forest 

 bed became entombed in growing peat. It is needless to say that the 

 evidence of these later changes is not restricted to Scotland. The bogs 

 of the two sister countries, and of the corresponding latitudes on the 

 continent, present us with precisely the same phenomena. 



The present decayed aspect of the bogs in many places where they 

 formerly flourished, and the fact that certain plants and groups of 

 plants are once more beginning to invade such wastes, shows that 

 we are now living under somewhat milder and less humid conditions. 



Although these later climatic oscillations certainly affected the dis- 

 tribution of plants and animals to some extent in northern and north- 

 western Europe, yet the changes brought about were insignificant as 

 compared with those which characterized the alternations of preceding 

 glacial and interglacial epochs. The earlier cold and genial stages 

 were strongly contrasted, and marked by great migrations of flora and 

 fauna. But, as the strange cycle drew to a close, the contrast between 

 glacial and interglacial phases became less and less pronounced and 

 gradually faded away into the present. The steppe fauna vanished 

 from middle Europe during the fourth interglacial epoch, and it never 

 returned. The climatic oscillations that followed were on too small a 

 scale to induce great migrations, and thus the succeeding forest fauna 

 retained its place. Hence in such a section as that seen in the rock 

 shelter of Schweizersbild, we find no recognizable evidence of the cli- 

 matic changes to which the buried forests and peat bogs and the small 

 local moraines of northern and northwestern Europe bear testimony. 

 It is thus only by correlating and comparing the evidence over the 

 widest area that we are able to get the story completed. 



In fine, we have seen that tundras and steppes appeared at successive 

 epochs in prehistoric Europe. The former were contemporaneous with 



