sheep brought into the impoverished communal treasuries seemed indispensable, though it was easy to see that it was bad economy to admit them. Such trampling and tearing weakened the turf so that it was every year more easily washed down-hill during heavy rain, and, when it went, the soil underneath went too. The farther down the mud and water rushed, the deeper and wider were the erosions. Upon the steeper slopes below, which should have been clothed with woods, the ravages were still greater. As like causes were operating in a similar way upon other surfaces in the same basin, after every heavy rain (especially if it fell upon deep snow) the streams suddenly rose thirty, forty, and even sixty feet, and then again, in a few hours, were at their old level.
If a bank overhanging the narrow gorge at the mouth of one of these mountain-basins was undermined and fell across the opening, a lake quickly formed behind, until the accumulating pressure burst the barrier, and then woe to the people down-stream! In one such dèbâcle the wave was one hundred feet high, and swept down the valley at the rate of fifty feet a second, or thirty-four and one eleventh miles an hour! "At one point the water was seen pushing before it a moving mountain of all kinds of débris of three hundred feet in height, from which was rising a thick cloud like the smoke of a conflagration" (Brown's "Reboisement in France," pp. 86-89).
Deprived by their own improvidence, or that of their parents, of their forest wealth, the mountaineers thought that they must starve, or else use every available acre for pasturage. Planting trees and waiting for them to grow required knowledge and capital, and they had little of either. The damage done by torrents was more severe farther down, although it all began in the uplands, whose turf was loosened by the starved sheep of the south. Lack of the timber which should have enriched and protected the zones just below these pastures made the mountaineers feel so poor that they felt constrained to take every sheep and goat which the lowlanders would bring. It was clear that they could not restrict the number of these "summer boarders" and at the same time reforest the steeper lower zones to the extent which was demanded by their own welfare, and still more by that of the people living farther down-stream.
This made it necessary for the state to step in. Under the feudal system it was held that a seignior, and especially a king, must possess one or more forests. In France, those belonging to the crown have become the property of the state, and, for the care of these there have gradually been trained a special class of officers. When the reboisement law of 1860 was passed, many of these were men of great attainments. Surell, born in the Département des Hautes-Alpes, was one of the most eminent among them. As an engineer he had long been familiar with the numerous and costly—and yet inadequate—mechanical expedients which had been tried by the authorities for the purpose of
