290 PROTECTION AGAINST AVALANCHES. 
its average thickness is thought to have been about a hundred 
feet. The highest portion of the mountain was more than 
three thousand feet above the village, and the momentum 
acquired by the rocks and earth in their descent carried huge 
blocks of stone far up the opposite slope of the Rigi. 
The Piz, which fell into the Cordevole, rested on a steeply 
inclined stratum of limestone, with a thin layer of calcareous 
marl intervening, which, by long exposure to frost and the in- 
filtration of water, had lost its original consistence, and become 
a loose and slippery mass instead of a cohesive and tenacious 
bed. 
Protection against Avalanches. 
In Switzerland and other snowy and mountainous countries, 
forests render a most important service by preventing the for- 
mation and fall of destructive avalanches, and in many parts 
of the Alps exposed to this catastrophe, the woods are pro- 
tected, thongh too often ineffectually, by law. No forest, in- 
deed, could arrest a large avalanche once in full motion, but 
the mechanical resistance afforded by the trees prevents their 
formation, both by obstructing the wind, which gives to the 
dry snow of the Staub-Lawine, or dust-avalanche, its first im- 
pulse, and by checking the disposition of moist snow to gather 
itself into what is called the Mutsch-Lawine, or sliding ava- 
lanche. Marchand states that, the very first winter after the 
felling of the trees on the higher part of a declivity between 
Saanen and Gsteig where the snow had never been known to 
slide, an avalanche formed itself in the clearing, thundered 
down the mountain, and overthrew and carried with it a 
hitherto unviolated forest to the amount of nearly a million 
cubie feet of timber.* Elisée Reclus informs us in his re- 
markable work, Za Terre, vol. i., p. 212, that a mountain, which 
rises to the south of the Pyrenzean village Araguanet in the upper 
valley of the Neste, having been partially stripped of its woods, 
a formidable avalanche rushed down from a plateau above in 
— 
* Bntwaldung der Gebirge, p. 41. 
