«EVUB DES EAtJX ET F0BET8, 91 



April 1866, the following striking illustration of the effect of woods on 

 torrents : — " The State possesses, in the department of Vancluse (says 

 the forest conservator, Labuissifere), a forest of more than 3000 hectares, 

 situated on the portion of the mountain Luberon nearest to the vaUey of 

 the Durance. This region is very much cut up, and traversed in all direc- 

 tions by very narrow and deeply embanked ravines in the midst of masses 

 more or less dense of Aleppo pines and green oaks. 



" These ravines are almost the only outlets for the transport of wood, in 

 consequence of the difficulties which would be encountered, and the expense 

 which would be incurred, in making more practicable ones on the rapid 

 declivities, strewn with enormous masses of rock. There exists one so 

 situated, called the Ravine de Saint-Phalez. The direction is from north 

 to south, in the midst of a mass of Aleppo pines, in a state of growth more 

 or less compact. 



" Its length, and for four kilometres, or from the road from CavaiUon to 

 Pertuis, to the domain of Saint-Phalez, of an area of about 50 hectares, 

 forms the basdn de reception of the torrent. 



" This land is well cultivated ; there are no declivities too steep for 

 cultivation ; it comprises vineyards, meadows, and arable land ; the soil is 

 argiQaceouB. 



" The ravine of Saint-Phalez receives many affluents, the most important 

 of which is that of the Combe-d'Yeuse, which joins it near the summit, 

 where are some hundred mfetres of the cultivated grounds of which I have 

 spoken. 



" The ravine de la Combe d'Yeuse is of much less considerable length 

 than that of Saint-Phalez ; it is scarcely two kilomtoes. It is strongly em- 

 banked, surmounted by steep declivities, covered with green oaks of eight 

 or ten years' growth, and with Aleppo pines of different ages. Its bassin de 

 reception, of about 250 hectares, or 113 acres, comprises the whole slope, 

 precipitately inclined, with a general south-west aspect ; it is closed at the 

 top by a deep bed of rock cut into peaks of the most imposing aspect. 



" The geological formation is absolutely the same, as are all the other 

 conditions, at all the points which I have examined. In no part is to be 

 seen either spring or appearance of humidity ; no water is seen excepting 

 at the time of the storms or great rains, and this water soon passes away, 

 with the differences which wiU afterwards be mentioned. At all other 

 times these ravines are of a desolating aridity. 



" In the night of the 2d and 3d of September 1864 there fell a rather 

 abundant rain over all this portion of the mountain. In the morning the 

 argillaceous grounds of Saint-Phalez were saturated, of which evidence was 

 found by anyone attempting to cross them. The ravine of Saint-Phalez, the 

 receptacle of the surplus water, had flowed but slightly ; that of the Combe- 

 d'Yeuse remained dry. 



" The day of the 4th September was very warm ; a water-spout borne 

 along by a south-west wind struck on the Luberon. Its passage did not 

 last more than forty minutes ; but scarcely had it come when the torrent 

 of Saint-Phalez became awful. Its maximum deliverance was about two 

 cubic metres. It did not flow more than fifty minutes, but with an average 

 delivery of half a cubic mfetre ; it had then passed in all 15,000 cubic 

 metres of water. Its height had been 0-04 m. ; each square mfetre had 

 received 40 litres, and the 50 hectares of Saint-Phalez 20,000 cubic mfetres. 

 The ground had only retained 5000, which is sufficiently explained by their 



