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WHATEVER differences of opinion may exist respecting the meteorological influence of forests, it is generally agreed that in mountainous countries they play an important part in regulating water-courses and in preserving the soil on the slopes of the hills. This function, which has been observed for a long time, was presented in a clear light by M. Surrell, engineer of bridges and highways, whose fine work on the torrents of the high Alps ("Torrens des Hautes-Alps"), published in 1841, has been the point of departure for all studies and all legal projects respecting rewooding. While the author had in view only the restoration of the French Alps, his conclusions are applicable, although in different degrees, to all mountainous countries; but the phenomena which he considers are manifested with the most intensity in the Alps, and the renewal of the woods there is imposed as a real measure of public policy.

In respect to vegetation, nature has divided the Alpestrian mountains into three zones: creating on the summits, around the rocks and glaciers, pasture-lands on the middle slopes, forests; in the lower valleys, lands suited to occupation by agriculture and by villages. Unfortunately, this natural division has been too often disturbed; the inhabitants, leaving the valleys, have established themselves in the higher regions, have cut down the forests around their houses, and devoted to cultivation lands which, disintegrated by the plow, are incessantly cut up into ravines by every rain; or the zone of pasture-lands has encroached on that of the forests, and has been increased by the daily devastations of the shepherds. Extending its borders every year lower down the mountain, it has finished by taking possession of the slopes and despoiling them of their wood. Gradually the grass itself, no longer protected by the cover of large trees and continually fed upon by hungry flocks, has disappeared, leaving behind it only the denuded flank of the mountain, an easy prey of which the torrents have not been slow to take possession.

The mountain-torrent is not an ordinary brook, but is a stream with characters of its own and peculiar ways. Originating in a narrow basin, the bed of which is very steep, it is subject to sudden variations;