640 THE UNIVERSE. 



ena : fire and ice are at war, and it is a struggle as to which 

 shall overwhelm the other. This happens in the inaccessi- 

 ble Erebus, a volcano of the polar regions, discovered by Sir 

 James Ross. Enveloped in snow and ice from the base to 

 the summit, and resembling an immense block of rock-crys- 

 tal, its crater is yet in perpetual activity. 



It is in these lofty mountain regions that we hear the 

 thunder of the avalanche growl, their most terrible and 

 most imposing phenomenon. Here the traveller may every 

 instant enjoy this grand spectacle, for it is almost incessant 

 wherever the snow and ice extend their covering over 

 slightly inclined smooth surfaces. 



Avalanches are generally formed by enormous masses of 

 snow, which from the height of the mountains precipitate 

 themselves into the valleys. It is particularly in spring and 

 during summer that they occur, at the time when the heat 

 of the day makes itself most felt. At such times the least 

 agitation in the air produces the fall. There has been only 

 too often occasion to regret their ravages ; they frequently 

 engulf travellers, and sometimes carry with them forests 

 and villages. 



In the mountain passes where there is most reason to 

 dread them, the muleteers always travel before day, the 

 time when they are least to be feared ; and in order not to 

 agitate the air they observe absolute silence, and even stuff 

 the little bells on the harness with linen. But, notwith- 

 standing these precautions, the avalanches engulf every 

 year a certain number of victims. At different times hun- 

 dreds of men have perished at once, crushed under their 

 mass. The most deplorable accident due to this cause upon 



