94 LITEEATUEK ON T0BHENT8. 



a considerable quantity of water, estimated at 24,000 cubic mfetres by M. 

 Cournaud, land surveyor; the warders bathed in it, and it was of such a depth 

 that they could swim in it. Unhappily, this water could not be retained, 

 in consequence of so many fissures in the rock and the rapid percolation 

 through the soil ; and they broke down this harrage, which had been built 

 with such great hopes, to facilitate the bringing out the timber of the last 

 exploitation in 1856. 



" In 1843 there was still water in the Combe-d'Yeuse ; there was no more 

 seen until 1856, but from this time onward the water flowed almost every 

 year only in small quantities. But the year 1862 must be excepted; 

 although much less rain fell than in 1864, it delivered much more water 

 into the ravine ; but this it did without causing damage worth speaking of. 



" The comparison of all these dates seems to me to supply valuable instruc- 

 tion. If the woods be young the ravine flows every year, often causing 

 thereby considerable damage. As their age augments it flows at intervals 

 more and more remote, and ends in being almost completely exting-uished. 



" These conclusions will not astonish foresters who have been accustomed 

 to the exploitations of copse wood. For, slight as may be the slope of the 

 ground with a light soil, the annual fellings are cut into ravines by a single 

 storm, whilst nothing like this is to be seen in the felling at its side, which 

 has grown for 20 or 25 years, according as the one or other of these rota- 

 tions of the fellings has been adopted." 



In 1849 there appeared a pamphlet by A. Marschand, entitled Ueber die 

 Entwaldung der Oebirge, which was published at Bern-; and in 1872 was 

 published, at Arbois, Les Torrents des Alpes et le Paturage, par M. L. 

 Marschand, Garde General des Porets, Ancien eleve de VEcole Porestiere. 



The preparation of this treatise was undertaken at the suggestion of M. 

 Far6, Directeur general de V Administration des Porets. It embodies the 

 results of observations made during a residence of seven years in the valley 

 of Barcelonette, and during a tour of observation in the Austrian Alps, and 

 observations made in Switzerland, whither M. Marschand had been commis- 

 sioned to go to complete his study of the subject. 



The attention of M. Marschand was given, primarily and chiefly, to 

 torrrents and the means to be employed to an-est and counteract them ; 

 attention was also given to pasturing of flocks and herds on the mountains 

 as the original cause or occasion of the destruction of forests, which destruc- 

 tion of forests had been followed by the appearance of the torrents in the 

 regions in which they are so numerous. Every facility was given to him 

 by the forest authorities, ofiicials, and subordinate employis, in the prosecu- 

 tion of his studies ; and he states that by them were furnished many of the 

 documents and ideas embodied in his treatise. 



M. Marschand appears to have been led to conclude that the effects pro- 

 duced by trees, observed by SureU aud others, was, primaiily and principally, 

 if not exclusively, produced by their roots ; and by these modifying the 

 hydroscopicity, capillarity, and permeability, of the soil and subsoil ; and 

 that this they did even when this ground was rock. And from this stand- 

 point he deals with the subject. 



Surell and others had given an exposition of what may be called the 

 mechaniofil efi'ects of the roots of trees in preventing the formation of 

 torrents ; he, while accepting this, was led to conclude that there was more 

 in this than had been evolved. 



