AND PEEVENTIVB MEA8UEES, 251 



will have given place to a sheet of limpid water, flowing into the torrent 

 above the barrage." 



While all the credit given to M. Costa by M. Cteanne is justly due to 

 him for devising and executing such works, it is also due to M. Surell to 

 mention that the sufficiency of such measures in some cases was not 

 unforeseen by him. In view of the whole subject of torrents, he remarkSj — 

 " When a torrent is examined with attention, it may be seen that all its 

 parts are not equally hurtful. The mischief is often committed by but one 

 branch of it, and the others contribute but little thereto. It would, then, 

 be useless to apply the same treatment to all without discrimination ; the 

 attack must be made on the devastating branch, and that once extinguished, 

 the ravages will be found to have ceased." 



From what has been stated, it will be seen that the work assumes a 

 variety of forms; but rehoisement seems still, as from the first and aU along, 

 to be considered the most important, if not the most necessary, of the 

 various forms which the work of extinguishing torrents assumes, or rehoise- 

 ment and gazonnement in combination ; and I would now report how the 

 work is being executed in the High Alps, where the importance of this 

 enterprise in all its magnitude has been realised by all classes of the 

 population. 



There, over the whole surface of the herges vives, sloping but often very 

 steep banks to be covered with vegetation, are traced horizontal level 

 banks, about 6 or 7 feet broad, with a slight inclination towards the moun- 

 tain, designed to give to the water facilities for collecting and remaining 

 there. Towards the edge of these banks, where previously the earth has been 

 loosened to a considerable extent by the pickaxe, they plant broad-leaved 

 trees of three or four years growth in such proximity to each other that 

 the extreme branches touch, and in such a way that the collet of the root 

 is buried some eight inches under the surface of the ground as a security 

 against drought. The stem is pruned to the level of the ground, that too 

 rapid vegetation may not exhaust the plants ; and the pruning is repeated 

 until the vigorous appearance of the young trees testifies that their roots 

 have at length reached a moist subsoil capable of supplying them with 

 nourishment. 



These embankments are made at distances from each other varying with 

 the degree of slope ; and the intermediate strip is sown broadcast with forage 

 plants, or plants chosen from amongst those which grow spontaneously on 

 the mountains. Sometimes, midway between the rows of trees, are planted 

 other hedges of trees which receive less attention, but which grow pretty 

 well in favourable spots ; and between these trees, and midway between 

 these rows, there may be planted lines of lucerne, while on the space 

 between grow herbs of various kinds. This is the case where the main lines 

 of trees are from 20 tu 100 feet apart. 



When the slope is very precipitous, the embankments are sustained by 

 stones or hurdles ; and when on steep declivities the soil is so disintegrated 

 as to be unable to withstand the violent impinging of the rain-drops in a 

 storm, the ground sown is sometimes protected by a covering of straw, 

 or with cuttings of herbs, &c., which the growth of the herbage underneath 

 soon renders unnecessary. 



M. Marscha!nd gives the following instructions, and refers to the Traite 

 Mementaire de Sylviculture of M. Franckausen, translated into French by M. 



