138 THE GLACIER SYSTEM. 



of ice Upon the slopes of its 'lofty hills the downy 

 snow-flake has become the hardened crystal ; and, in- 

 creasing little by little from year to year and from 

 century to century, a broad cloak of frozen vapor has 

 at length completely overspread the land, and along 

 its mde border there pour a thousand crystal streams 

 into the sea. 



The manner of this glacier growth, beginning in 

 some remote epoch, when Greenland, nursed in 

 warmth and sunshine, was clothed with vegetation, 

 is a subject of much interest to the student of physi- 

 cal geography. The explanation of the phenomena 

 is, however, greatly simplified by the knowledge which 

 various explorers have contributed from the Alps, — 

 a quarter having all the value of the Greenland moun- 

 tains, as illustrating the laws which govern the for- 

 mation and movements of mountain ice, and which 

 possesses the important advantage of greater accessi- 

 bility. 



It would be foreign to the scope and design of this 

 book to enter into any general discussion of the vari- 

 ous theories which have been put forth in explanation 

 of the sublime phenomena, which, as witnessed in the 

 Alpine regions, have furnished a fruitful source of 

 widely different conclusions. It was, however, easy 

 to perceive in the grand old bed of ice over which I 

 had traveled, those same physical markings which had 

 arrested the attention of Agassiz and Forbes and Tyn- 

 dall, and other less illustrious explorers of Alpine gla- 

 ciers ; and it was a satisfaction to have confirmed by 

 actual experiment in the field the reflections of the 

 study. The subject had long been to me one of great 

 interest; and I was much gratified to be able to make 

 a comparison between the Alpine and Greenland ice. 



