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CHAPTER, II. 



PROTECTION AGAINST AVALANCHES.* 



1. Origin. 



AVALANCHES are caused by the loosening and fall of masses 

 of snow or ice on steep smooth slopes in mountainous regions ; 

 they may consist of loose or massive snow, or both combined, 

 or of ice from broken glaciers. 



a. Avalanches of Loose Snow. 



These are locally termed Staublawinen, and occur in 

 November, when fine dust-like snow is falling ; they are due 

 to great steepness of the mountain sides, or to overhanging 

 masses of snow falling on to rocks, the snow being separated 

 into dust during its fall. They are of rarer occurrence than 

 other avalanches and seldom cause any damage. 



b. Avalanches of Massive Snow. 



Movements of the upper layer of massive snow, termed 

 Oberlawinen, occur chiefly from December to February, when 

 thick layers of fresh snow have fallen on to old frozen snow, 

 and become so weighty that they can no longer rest on the 

 smooth base beneath them. 



c. Ground Avalanches. 



When masses of snow which extend down to the surface of 

 the ground, roll or slide down a mountain side, they are 

 termed Grundlawinen, and are extremely dangerous. They 

 generally fall towards the end of winter at midday, during the 

 melting of the snow, and when a Fohn, or south wind, is 



* Landolt, El., " Die Bache, Schneelawinen u. Steirischlage." Zurich, 1886. 

 Pollack, Vincenz, " Die Lawinen Oesterreichs und der Schweitx uml deren 

 Verbauungen." Vienna, 189^. 



