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CHAPTEli 11. 



PROTECTION AGAINST AVALANCHES.* 



1. Origin. 



Avalanches are caused ])y 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. 



n. Avaldiiches of Loose Snoiv. 



These are locally termed Stauhlaivincn, and occur in 

 November, wlien 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 duh't during its fall. They are of rarer occurrence than 

 other avalanches and seldom cause any damage. 



b. AvaJamlirs of Afassire Snow. 



Movements of the upper layer of massive snow, termed 

 Oherlawinen, 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. 



r. (tioinid Ara/aiirhcs. 



AVhen masses of snow wliich extend down to the surface of 

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

 termed Grimdlawinen, and are extremely dangerous. They 

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

 melting of the snow, and when a 7'V;////, or south wind, is 



• Landolt, El., " Die Bachc, Sclmcelawinen u. Steiiischlage." Zurich, 188(5. 

 Pollack, Vincenz, " Die Lawinen Oesterreichs unci dcr Schweitz und deren 

 Vcrbauunpeii." Vicuna, ISDl. 



