390 CLIMATIC CONDITIONS OF THE GLACIAL EPOCH. 



those which now prevail in that range, where there was no advance of the 

 ice beyond the limits of the range itself, and where the glaciers themselves 

 still remain, having a development not much inferior to that which they had 

 during the Glacial epoch. 



In the Sierra Nevada of California, again, we have now precisely similar 

 topographical conditions to those which existed at the time large glaciers 

 were developed there ; but these have entirely disappeared, leaving hardly 

 the feintest traces of their former existence so for as the actual presence 

 of ice is concerned, but abimdant proof of it in the form of moraines, strioB, 

 and other easily recognized phenomena. Here we find still a condition of 

 things in harmony with itself, and not presenting any serious difficulties as 

 regards explanation. The decrease and disappearance of the glaciers in the 

 Sierra Nevada is an occurrence in close relation with the desiccation which 

 has long been going on in the adjacent region on the east. It is but a short 

 time since the ice disappeared. Indeed, it may be said without the slightest 

 fear of error that this disappearance took place long after the existence of 

 the human race began in that region, and that when these glaciers were 

 at their maximum the valley at the base of the range was no less habitable 

 than it now is, and that nothing whatever indicates that a " Glacial epoch " 

 ever prevailed there, or that the character of the vegetation underwent any 

 essential change immediately before or after the time when ice covered the 

 summits of those mountains. 



Passing to the Alps, however, we find ourselves in the presence of more 

 complicated phenomena. The past glaciation was indeed subordinate to the 

 topography, and the glaciers have by no means disapjjeared, although much 

 reduced in size. If the ice flows at the time of their greatest development 

 passed beyond the limits of the range and spread themselves on the ^^hiin 

 at its base, as supposed by some, this did not take place on any very exten- 

 sive scale, so that the condition of things during the Alpine Glacial epoch 

 was not one difficult of comprehension. At least we are not obliged to 

 assume that the earth's climate underwent a radical change, because there 

 were ice flows four or five times as long as any now existing. The ex- 

 traordinary amount of shrinking which these glacial masses have undergone 

 within the past fifty years, without any perceptible corresponding climatic 

 change, is sufficient proof of the correctness of this view. 



The Scandinavian glacial development was decidedly more complicated 

 and on a grander scale than the Alpine ; but the principal focts connected 



