December 9, 1891.] 



Garden and Forest. 



585 



the necessity of modifying a condition that formed a singular 

 contrast with the prosperity of other regions and threatened 

 to compromise them also. 



The government was apathetic, and, heedless of danger, con- 

 tinued to ignore a matter which seemed to interest only some 

 poor districts crying faintly in their distress. But, at length, 

 the disastrous inundations of 1840 brought from the lower 

 Alps another cry of alarm that suddenly aroused public 

 opinion. 



A young engineer, Surrell, originally from the most densely 

 forested district of Lorraine, published, under the guidance of 

 Dufaure, then Minister of Public Works, his " Etude sur les 

 Torrents des Hautes-Alpes." This masterly work was charac- 

 terized by the most thorough analysis, the clearest observa- 

 tions, the most definite conclusions and the most advanced 

 ideas of economy. It was the grandest plea ever uttered in 

 favor of mountain-forests, and was awarded a Montyon prize 

 by the Institute in 1842. 



From that time the reforestation of mountains has taken rank 

 among matters of high public interest in France ; the government 

 brought this important question to the attention of the general 

 councils of many interested Departments, and the Forest-ad- 

 ministration, while preparing a code of law, began in 1846 a 

 series of experiments in reforestation, the results of which 

 have not ceased to be of value. Political events caused a long 

 delay, and it was not until i860 that a permit for experimentation 

 was granted. This was the first law looking toward the refor- 

 estation of mountains, and it was the result of aroused public 

 opinion after the inundations of 1856, the losses by which have 

 been estimated at more than 250,000,000 francs. There were 

 clamorous politicians who maintained that reforestation of 

 mountains was a chimerical and impracticable enterprise, 

 which would only lead to disappointment. But the govern- 

 ment was gaining knowledge from the experiments, and by 

 1876 it was able to lay before Parliament a new plan, which, 

 after many debates, resulted in the law of April, 1882, for the 

 Restoration and Preservation of Mountain Lands, in full force 

 to-day. 



The provisions of this law are of two classes : (1) Measures of 

 encouragement, which consist in the power given the govern- 

 ment to incite, by means of bounties, landed proprietors.commu- 

 nities and private citizens to improve lands hitherto unproduc- 

 tive, desolate and liable to erosion. (2) Measures of coercion, 

 which authorize the state to demand the declaration of the 

 public need of works termed "obligatory" at all points where 

 a careful investigation shows that their execution is demanded 

 by deterioration of the soil and real dangers. 



If we investigate the causes of deterioration we find that the 

 great enemy, in fact the only one that we have to combat, is 

 erosion, the power of which is determined by the inclination 

 of the slopes, the volume of water that may flow in a given 

 time, and the friability of the soil or of the underlying rock. 

 The maximum effect is accomplished by a torrent — that is to 

 say, a stream of water with very steep beds and sometimes in- 

 termittent — conditions which give the greatest power to erode 

 and transport from the mountains the materials which the 

 stream deposits in the valley. This notable characteristic of 

 the torrent helps to make the floods in the plains still more 

 resistless by the enormous mass of solid material, which, 

 washed into the rivers, increases the volume of their flood 

 and constantly elevates their bed. 



The problem of restoring and preserving mountain-lands 

 must necessarily be stated thus : On one hand to sup- 

 press in existing torrents the possibility of erosion, and the 

 consequent transportation of material, and to diminish the 

 volume and the suddenness of floods — that is to say, to trans- 

 form the torrents into harmless and even beneficial streams ; 

 on the other hand, to anticipate or to prevent all erosion 

 which may give rise to either the formation of new, or to 

 the renewed activity of extinct torrents. 



Such a delicate enterprise should, therefore, not be left to 

 the discretion of the owners of the soil, but should be carried 

 on by some agency of wider authority. Hence these obliga- 

 tory reforestations prescribed by the law, which gives to the 

 state, in case of the refusal, the negligence, or the inability of 

 the private owner, the duty of preparing for the formidable 

 struggle, which it alone will be able to carry on with success. 

 Upon the state, therefore, devolves the restoration of torrent- 

 worn mountains. 



It was estimated in i860 that the area of denuded mountains 

 needing reforestation would reach 2,964,000 acres. After the 

 extensive surveys from 1884 to 1886, covering 8,645,000 acres, 

 the total area to be placed under management by the state was 

 fixed at about 790,400 acres, or a fourth of the whole area to be 

 reforested. The operations upon the lands most needing 



them, however, will cost more than the reforestation of the 

 three other fourths, which are to remain in the hands of their 

 present owners and be made valuable by means of the state 

 bounties. 



Before going too far, it may be well to define clearly certain 

 terms of our special vocabulary : 



We say of a torrent that it is "in activity" when it erodes 

 near its sources, deposits material of all sorts in the valley, and 

 spreads out over its deposits. 



We call a torrent " extinct," which, after a period of activity 

 (be it long or short), becomes, owing to special circumstances, 

 no longer able to transport eroded material, but has longer 

 periods of high water, rising less suddenly and in diminished 

 volume, so that it passes into the condition of a brook. 



By " correction of a torrent," we mean the construction of 

 certain works which give stability to beds and banks in or- 

 der to arrest or to diminish the transportation of materials 

 and to reduce the rapidity of drainage. 



Finally, we distinguish among " active " torrents two differ- 

 ent modes of action, according to the nature of their floods. 

 In case the volume of water is greater than the volume of the 

 materials it carries, the latter stop one after the other, as their 

 resistance exceeds the transporting power. The coarser are 

 left first on steep slopes, then pebbles, gravels and sands, as 

 the grades grow less and less, the change of grade being well 

 shown by the upward concavity of the profile of their beds. 

 On the other hand, in the case of violent and sudden torrents, 

 from the rapid melting of snow, or a hail-storm, where the 

 volume of materials is much in excess of the volume of water 

 (perhaps double or triple), the current maybe seen in the form 

 of mud more or less thick, in which rocky materials of all dimen- 

 sions nearly touch, and which on very steep slopes are borne 

 onward en masse. When this current flows into the valley, 

 no longer confined between high banks, and reaching more 

 gentle slopes, it slackens. But the larger rocks, by virtue of 

 their acquired velocity, are less inclined to stop, and the dep- 

 osition of material is in this case in exactly the reverse order 

 of that by selection in regular floods. 



The very characteristic name of washes, or washouts, is 

 given to these strange floods which sometimes cross the 

 river to which the torrent is tributary, dam it for the moment 

 and leave on the opposite bank great fragments of their ad- 

 vance-guard, which remain for years in testimony of the vio- 

 lence with which they have been swept along. 



The field of action affected by the forester covers in great 

 part three mountain systems in the south of France : The Alps, 

 the Cewennes and the Pyrenees. 



I. — THE FRENCH ALPS. 



The group of the French Alps presents all possible forms of 

 erosions, washings, land-slides and other devastations that the 

 torrent is able to produce in the most diverse climates, and 

 at various altitudes from the sea up to perpetual snow. This 

 is the classic land of torrents, which there rule as terrible 

 masters, to accomplish what Michelet strikingly called " la 

 mort de la montagne." 



In 1846 the illustrious economist, Blanqui, in a report to the 

 Academy of Science, by which he had been charged with a 

 special study of the situation in the French Alps, made a start- 

 ling representation, from which I make some extracts. 



" One who descends from Dauphiny toward Provence, along 

 the summit of the Alps, is delayed at every step by the wild 

 irregularities of the mountains. In nearly a hundred leagues 

 he does not find a single navigable stream, not one of those 

 great basins, like those of the Marne, the Saone, or the Yonne, 

 which give life to whole provinces. The rivers of the Alps 

 partake of the character of torrents, by reason of their 

 rapid descent and their capricious course over a bed ob- 

 structed by rounded stones. Such are the Drac, the Ro- 

 manche and the Durance, into which are discharged, through 

 innumerable affluents, the melted snows from the perpetual 

 glacial reservoirs, and the rains of all the upper region. 



" The Rhone receives, in the lower part of its course, the 

 astonishing product of these great floods which have acquired, 

 in these later years, such alarming proportions. 



"The bright clear skies of the Alps of Embrun, of Barcelo- 

 nette, and of Digne remain, during entire months, free from 

 the least cloud, and engender long droughts only broken by 

 storms as violent as those of the tropics. The soil, deprived 

 of herbs and trees by pasturing and by clearing, and dried by a 

 burning heat, is washed quickly to the bottom of the valleys, 

 sometimes in the form of lava — black, yellow, or reddish — 

 followed by streams of pebbles and even by enormous rocks, 

 which bound impetuously on with horrible crashing and de- 

 struction. 



