PROTECTIVE MEASURES. 617 



blowing, and frequently during a storm. These are the 

 commonest and most dangerous avalanches, and leave tracks 

 which can be readily observed, as they occur over and over 

 again at the same places. 



d. Glacier- Avalanrhes 



Consist of broken fragments of glaciers. 

 The following remarks apply only to avalanches of massive 

 snow and ground avalanches. 



2. Dtiiudtie done. 



The damage done to foresfs by avalanches consists in the 

 breakage of all woods lying in their way, and in the obstruc- 

 tion of streams and roads which they cause. The rush of air 

 that accompanies an avalanche is so great that it breaks 

 many trees up to a distance of several hundred yards from the 

 avalanche. Many ibex are also killed b}^ avalanches. No 

 forest can withstand the rush of a large mass of snow down 

 the mountain side, and the higher, smoother and steeper, and 

 freer from wood a mountain-side is, the greater the danger 

 of avalanches, and the greater the rapidity with which they 

 fall. 



A high soil-covering of hill grass affords considerable 

 protection. 



In the winter of 1875-76, in the district of liagaz, of the 

 Swiss canton Graublinden, 500 avalanches occurred, and in 

 the district Schuls of the same canton, 881 avalanches. The 

 winter of 1887-88 was also distinguished by the number of 

 avalanches which fell — 1,094 avalanches, chiefly between 

 February and April, of which 871 (80 per cent.) extended to 

 forests. On an area of 3,300 acres, 2,870,000 cubic feet of 

 timber was broken and U])rooted. The damage done by the 

 avalanches was valued at £17,220. 



In Austria, during the winter 1887-88, damage by 

 avalanches was done to the extent of £28,000. 



3. Protective Cidtand Measures. 

 (a) The surface above the tree-limit should be iixed by 

 sowing grass. In order to afford a sufficient obstacle to the 



