LBS TOBBENTS DBS ALPES, BY MABSCHAND. 99 



the depth of the raTine : descending to the forest zone uniformly extended 

 over the soil, they are there absorbed. 



" In a word, the zone of the forest absorbs generally the water flowing 

 from the zone of pasture lands which correspond to it. In support of these 

 observations, I appeal to all who, in the Alps, have observed storms of rain 

 in the forest. I except water accumulated in ravines or depressions, which 

 are in another condition. 



" But the beneficent action of the forests does not limit itself to this ; the 

 flow in the ravine may also, if it be not completely absorbed, be by them 

 rendered less injurious if it should come to spread itself over a cone de dejec- 

 tion in a forest otherwise covered with wood. I have observed, in connection 

 with this, numerous muddy floods in ravines which, spreading themselves 

 out in the middle of a forest, come out thence very limpid, depositing in it 

 their slime, and leaving in it also almost the whole of the water. 



" The great forest of the Ofen, in the Grisons, has supplied me with many 

 instances of this. The soil, composed of the dolomite limestone of the 

 triassic period, is somewhat unstable ; in the middle of the pasture lands 

 which surmount the forest there are formed every year numerous torrents, 

 which to an enormous extent carry off the small pebbles, which are charac- 

 teristic of the dolomite. All these torrents arriving in the forest, then expand 

 and diffuse themselves, and very rarely do they penetrate to the bottom of 

 the valleys. In the upper portion of the Munster-Thal, I have seen on the 

 right-hand side an enormous ravine, the muddy torrents of which are 

 arrested by the forest. And the waters of the Munster, so well enclosed at 

 this point, are a proof of the beneficial action of the forests. In fine, from 

 the moment that the forests begin to retain the mud they retain also 

 temporarily the greater portion of the water in which this was suspended, 

 which are arrested by the enormous absorbent powers they possess." 



Facts in accordance with some of these latter statements have been 

 observed and recorded by others. 



M. Marschand makes the following remarks on The Influence of Vegetation 

 on the Flow of Water : — 



" Gazonnbment. — Many people suppose that on the steep parts of the Alps 

 a good ffazonnement would be enough to keep up the soil and put an end to tor- 

 rents. Experience has shown me ihskiffazonnement alone is nearly always power- 

 less to moderate sufficiently the action of water flowing over steep declivities. 



" I have been surprised at storms when passing tliough meadows fit for 

 being mowed, situated at 2200 metres altitude — that is to say, above the 

 forest region. After some minutes, if the storm was pretty violent, the 

 water ran off the turf, collecting in the depressions of the ground, and 

 forming small clear torrents. On the 17th August 1869, in particular, I 

 observed in the upper basin of the Tinee, in the Maritime Alps, a storm of 

 wind and hail which hardly lasted half-an-hour, but which gave rise in the 

 meadows to a number of these little torrents, the junction of which would 

 produce a very considerable rise in the Tinee. 



" A storm observed at the same point in October 1868 threw immense 

 masses of water into the same river in spite of the perfect gazonnement of 

 its upper basin ; the same storm caused great havoc in the upper basin of 

 the valley of Abrifes, among the pastures on the hill of Grange-Commune. 

 Two of my friends had great difficulty in crossing the meadows situated 

 near the summit, so large were the torrents which had suddenly formed. 



