4 IN STARRY REALMS. 



of the surrounding conditions. The facts, so far as they 

 are known to us, fail to show any grounds for supposing 

 that there have been any important changes in the climates 

 of the earth within historic times. We have geological 

 evidence far earlier than any historical testimony as to the 

 character of the climates which prevailed at various epochs 

 of remote antiquity. The records of the rocks demon- 

 strate unquestionably that our globe has passed through 

 many striking vicissitudes so far as heat and cold are con- 

 cerned. Those records prove that there have been periods 

 during which some of the fairest regions of this globe 

 were desolated by a frost so intense that they became 

 thickly cased with solid ice. There have also been periods 

 when conditions of an opposite character have prevailed. 

 The polar regions which now seem the perennial abode 

 of impenetrable ice once enjoyed a succession of long 

 and delightful summers, diversified by winters remarkable 

 alike for their brevity and their mildness. The Arctic 

 solitudes, now so dismal and so barren, then nourished 

 plants and animals that can only thrive under genial con- 

 ditions of climate. 



No doubt the question as to the origin of these great 

 climatic changes, which have so frequently occurred in 

 the course of geological time, presents many difficulties. 

 Opinion is divided as to what the cause of these changes 

 may have been. I do not now enter into this subject, 

 because for our present purpose it suffices to note one 

 very important conclusion. Those who are competent to 

 pronounce on the question of the cause of the geological 

 variations of climate are in substantial accordance with 

 the view that several changes have not been due to anv 



