103 UTEBATUBE ON TOEBBNTS. 



as is maintained by opposing parties, which discussion he concludes with 

 the statement that he deems it would be wise, in existing circumstances, to 

 hold by these words with which Gay-Lussac replied to Arago, before the 

 .Commission of Enquiry of 1836 : — " According to my opinion there has not 

 yet been obtained any positive proofs that woods have by themselves an 

 actual influence on the climate of a great country, or of a special locality, 

 or that they have an influence different from that of vegetation of every 

 kind. The questions involved are so complicated, when we face them under 

 the climatic point of view, that the solution of them is very difficult, if 

 we may not say impossible." 



The third chapter is devoted to the consideration of the effects of forests 

 on the rainfall. In this he alleges that in so far as this is effected by 

 mountains it is less the local elevation than the local inclination of a place 

 by which the effect is produced, and that the effect of this is different 

 according as the pluvial cloud may be ascending or may have commenced 

 its descent ; and this, he contends, is an important element to be employed 

 in the correction of pluviometrical observations. He considers that the 

 effect of forests on the quantity of rainfall must be infinitesimally small, 

 and that numerous corrections, some of which he specifies, must be made 

 upon pluviometrical observations before they can be made available for a 

 satisfactory solution of the question raised. 



In succeeding chapters are discussed evaporation, infiltration, ruisselle- 

 ment, or the source and flow of water in water-courses, with the action of 

 forests on each of these, and the result of such actions, which he sums up 

 thus : — " This action depends on circumstances peculiar to each water- 

 course, and even to each afluent. This action is proportionally more 

 certain and more energetic according as the water-course is more torrential. 



" But what it is impossible to deny, and is beyond all dispute, is the 

 influence which forests exercise in conserving the soil of the mountains 

 against being washed away. In doing this, and preventing the formation 

 of ravines, forests modulate the Sow of the waters. And this supplies the 

 only certain criterion we have of the utility of forests in this connection." 



The chapter which follows reports what was done in the ten years 

 following the passing of the law of 1860, including the passing of the law 

 in regard to gazonnement, with details of the circumstances which led to 

 this; which chapter he concludes with the remark — "After such testimony 

 one cannot feel free to doubt that the operation is good, seeing that it 

 satisfies everybody — the Administration, men of science, and the people." 



In another chapter he reports the work done, and results obtained in 

 connection with the artificial extinction of torrents. 



Then follows an analysis of a memoir by M. Guiny, sub-inspector of the 

 exploitations of the mountains thus redeemed, which appeared in the Reme 

 des eaiix et forets, for 1865, with remarks of his own in support of the 

 proposal to substitute cows for sheep, and more especially for the immi- 

 grant sheep from Provence, the pasturing of which is destructive and 

 unremuuerating. 



This is followed up by similar analyses, with remarks of Mudes sur les 

 torrents des Hautes Alpes, par M. Scipion Gras, and of Memoire sur les 

 barrages de retemie des graviers dans les gorges des torrents, par M. Pldlijype 

 Bretoti, and of Rapport au counseil federal sur les torrents des Alpes Snisses 

 inspectes en 1858, 1859, 1860, et 1863, par M. le Professetir Culmanrir-^ 

 works relating chiefly to torrents to which gasonnmmt and boisemmt 



