108 ICE AND GLACIERS. 



magnificence of those scenes will make you the more 

 inclined to lend a willing ear to the remarkable results of 

 modern investigations on the more prominent phenomenci 

 of the glacial world. There we see that minute pecu- 

 liarities of ice, the mere mention of which might at other 

 times be regarded as a scientific subtlety, are the causes of 

 the most important changes in glaciers ; shapeless masses 

 of rock begin to relate their histories to the attentive ob- 

 server, histories which often stretch far beyond the past of 

 the human race into the obscurity of the primeval world ; 

 a peaceful, uniform, and beneficent sway of enormous 

 natural forces, where at first sight only desert wastes are 

 seen, either extended indefinitely in cheerless, desolate 

 solitudes, or full of wild, threatening confusion an arena 

 of destructive forces. And thus I think I may promise 

 that the study of the connection of those phenomena of 

 which I can now only give you a very short outline will 

 not only afford you some prosaic instruction, but will 

 make your pleasure in the magnificent scenes of the high 

 mountains more vivid, your interest deeper, and your 

 admiration more exalted. 



Let me first of all recall to your remembrance the chief 

 features of the external appearance of the snow-fields and 

 of the glaciers ; and let me mention the accurate 

 measurements which have contributed to supplement ob- 

 servation, before I pass to discuss the causal connection of 

 those processes. 



The higher we ascend the mountains the colder it becomes. 

 Our atmosphere is like a warm covering spread over the 

 earth ; it is well-nigh entirely transparent for the lumi- 

 nous darting rays of the sun, and allows them to pass almost 

 without appreciable change. But it is not equally pene- 

 trable by obscure heat-rays, which, proceeding from heated 

 terrestrial bodies, struggle to diffuse themselves into space. 

 These are absorbed by atmospheric air, especially when it 



