46 biSsumjS of subbll's study op 



of forests, and the influences of forest clearings and pasturage, — ^foUomng 

 the whole with a chapter devoted to illustrations and applications of the 

 warning to be derived from the case of D6voluy, which I have previously cited. 



The whole tone and spirit of these chapters produces an impression that 

 the exposition of the view given is not only the result of a prosecution of 

 the study of the subject, but probably an exposition of what first gave to him 

 a clue to the discovery of all he subsequently discovered in regard to the 

 natural history of torrents, and the appropriate measures for extinguishing 

 them and preventing their ravages. 



I have often pictured him to myself as one day plodding along, gradually 

 ascending a mountain valley, in the discharge of his professional duties, his 

 thoughts being at other times full of the subject of torrents and their 

 numerous phenomena, but on this occasion thinking on anything but these. 

 When, standing for a moment to rest and wipe away the sweat from his 

 brow, looking back he sees what he cannot but perceive is an old torrent 

 deposit — a veritable lit de d&jection — though overgrown now with shrubs 

 and herbs, with here and there cottages, and cottage gardens, and cotter's 

 fields. There it is ! He feels he cannot be mistaken. Who would have 

 thought to see it there and see it thus 1 But there is the cone-like forma- 

 tion, the fan-like expansion spreading from the outlet of the gorge ! Here 

 is food for thought, and he goes on his way rejoicing. He comes upon a 

 lesser lit de d&jection of recent formation ; how like and yet how different I 

 Here all is desolation ; there all_^was clothed in living green, and the opening 

 beyond showed a young and vigorous growth of trees. But stop ! May not 

 this have had something to do with the extinction of the torrent, and that 

 more as cause than as effect ? This is something to be thought about — I 

 leave to others to follow out the train of thoughts thus begun. I find no 

 difficulty in doing so till I picture to myself Surell master of the whole 

 subject in all its details, and it is with these, his matured views, irrespective 

 of the way in which they have been attained, that we have here to do. 



Writing on the influence of forests, or of the absence of forests, on the 

 fomiation of torrents, he says, — " When we examine the lands in the midst 

 of which are scattered the torrents of recent origin, we see them to be in 

 every case stripped of trees and of all kinds of arborescent vegetation. On 

 the other hand, when we look at mountain slopes which have been recently 

 stripped of woods, we see them to have been gnawed away by innumerable 

 torrents of the third class, which evidently can only have been formed in 

 later years. 



" See then a very remarkable double fact : everywhere where there are 

 recent torrents there there are no more forests ; and wherever the soil has 

 been stripped of wood recent torrents have been formed ; so that the same 

 eyes which have seen the forests felled on the slope of a mountain have 

 there seen incontinently a multitude of torrents." 



The names of numerous mountains and torrents, illustrative of both 

 allegations, are given. 



" The whole population of this country may be summoned to bear testi- 

 mony to these remarks. There is not a commune where one may not hear 

 from old men, that on such a hill-side, now naked and devoured by the 

 waters, they have seen formerly fine forests standing, without a single torrent. 



" Observations which are reproduced so often, and with characteristics so 

 constant, can we explain as simply the result of chance ? Do they not force 



