Lbs TOEREtJTS, ETC., Bt COSTA Dfe BASTBtlCA. Ill 



deposits ; they had nothing to fear from the principal river, which flowed 

 thrdugh the lower-lying lands, nor from the torrent, which was then extinct ; 

 they commanded the plain, and found themselves at the gate of the moun- 

 tains ; the adjacent gorge supplied them with water, the forest supplied 

 them with wood, the rock supplied them with stone, and their flocks spread 

 themselves over the verdant ridges around them. 



" Little by little, a reckless use of the forests and of the pasturage 

 disturbed the equilibrium of the natural forces ; and now the old sore is 

 re-opened, and anew, Dy man's deed, the mountains are inoculated with the 

 leprosy of the torrents. The evil has gone on increasing during prolonged 

 ages of disorder and recklessness ; the position of the cultivated grounds, 

 and of the villages established at the ddbouche of the torrents, has now 

 become critical in the extreme ; and unless we go back, as we have done, 

 to the olden times, we are unable to account for men having taken up their 

 dwelling in the spots, of aU others, which at this day appear to be those 

 which are more immediately threatened. 



" But at last an era of reparation begins ; and, thanks to the eminent 

 men who have in byegone years given their mind to the work, the next 

 generation may hope to see the final decline of the modem renewed 

 Torrential Era." 



In 1874 was published Les Torrents leur lois, leur causes, lew effets : Moyens 

 de les reprimuer et de les utiliser : leur action geologique universelle, par Michel 

 Costa de Bastelica, Conservateur des Eaux et Forets. 



This work treats of another aspect or of another department of the subject 

 than any discussed in the treatises already mentioned, which the author 

 designates, — Le pMnomine torrentiel, or la torrentialiii ; and thus is opened 

 up another chapter of the natural history of torrents. 



" The question raised by torrents," says M. Costa, in the introduction of 

 the work, " is a very complex one. Behind the technical questions embraced 

 by it, there are others which connect themselves with the forest economy, 

 and with the pastoral occupations and the agriculture of the inhabitants of 

 the mountains, and which involve serious difficulties of administration and 

 of legislation. To operate on the basin of torrents brings one in contact, and 

 sometimes into collision, with the requirements and the customs of the 

 population. The two spheres of thought are quite distinct. The technical 

 element of the question is admitted to be the more important of the two, 

 and it is made the basis of the system of operation. I shall, therefore, con- 

 fine myself exclusively to it. It will be easy to remove the difficulties of 

 another kind, which beset practical operations under the requirements of 

 the case, when it shall be demonstrated by science, and estabUshed by 

 experience, that it is possible to put a stop to the outburst of water-courses 

 by a combination of simple works, comparatively inexpensive, and wisely- 

 devised conservative measures. 



" With this view I desire to give synthetically the fundamental idea of 

 the new torrential theory. 



" It has struck me in all preceding discussions, in regard to hydrology in 

 general, that they relate almost exclusively to the debit, or quantity of water 

 passing or delivered; it is admitted that they take into account the materials 

 born6 along by the currents at the time of floods ; but on the whole the 

 supposed cause of inundation is always spoken of as the excess of the 

 delivery over what it is at other times. All the discussions which have 



