FORESTRY BUREAU. 



161 



in the case of two streams whose ttasins are situated very near each 

 other, one of which is well wooded, while from the other the forest-cov- 

 ering has been removed. The case is so interesting as to warrant quot- 

 ing an account of it from the Revue des Eaux et Forcts: 



The state possesses, in the department of Vauoluse (writes the forest conservator 

 La 13uissiere), a forest of more than 3,000 hectares, situated on the portion of the 

 mountain Luberon, nearest to the valley of the Durance. This region is very much 

 cut up, and traversed in all directions 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 conse- 

 quence of tho difficulties which would be encountered and the expense which would 

 bo 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 4 kilometers, or from the road from Cavailloi?. to Pertuis, to the 

 domain of Saint-Phalez, of an area of about 50 hectares, forms the bassin 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 argillaceous. 



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 hun- 

 dred meters of the cultivated grounds of which I have spoken. 



The ravine de la Combe d' Yeuso is of much less considerable length' than that of Saint- 

 Phalez ; it is scarcely two kilometers. It is strongly embanked, surmounted by deep 

 declivities, covered with green oaks of eight of ten years' growth, and tho Aleppo 

 pines of different ages. Its bassin de reception, of about 50 hectares, or 123 acres, com- 

 prises the whole slope, precipitately inclined, with a general southwest aspect. It is 

 closed at the top by a deep bed of rock cut into peaks of the most imposingaspect. 



The geological formation in both is absolutely the same, as. are all the othtff condi- 

 tions at all the points which 1 have examined. 



In no part is to be seen either spring or appearance of humidity. No water is seen 

 excepting at the times of storms or great rains, and this water soon passes away, with 

 the differences which will afterwards be mentioned. At all other times these ravines 

 are of a desolating aridity. 



In the night of the 2d or 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 any one attemptingto 

 cross them. The ravine of Saint-Phalez, tho receptacle of the surplus water, had 

 flowed but slightly ; that of the Combe d' Yeuse remained dry. 



The day of the 4th of September was warm; a water-spout borne along by a south- 

 west wind struck on tho Luberon. Its passage did not last more than forty minutes ; 

 but scarcely had it come when the torrent of Saint-Phalez became awful. Its maxi- 

 mum deliverance was about 2 cubic meters. It did not flow more than fifty minutes, 

 but with an average delivery of a cubic meter ; it had then passed in all 15,000 meters 

 of water. Its height had been 0.04 m.; each square meter had received 40 liters, and 

 the 50 hectares of Saint-Phalez 20,000 cubic meters. The ground had only retained 

 5,000, which is sufficiently explained by its argillaceous character and the state 

 of saturation the night before. While tho torrent of Saint-Phalez flowed, filled from 

 bank to bank, seizing and carrying off rocks which had been employed to form a road 

 which was believed to be safe against all contingencies, that of the Combe d'Yeuso 

 and all those traversing the wooded lands remained dry, or gave only an insignificant 

 quantity of water. 



On the slope opposite to that of which I have been speaking, in the valley of Peyne, 

 a carriage road newly formed did not experience the least injury throughout tho 

 whole of the portion of it passing through the forest of the domain; but at its issue, 

 on the lands of the Libande and of the Roquette, it had been, so to say, destroyed. 

 A cart loaded with fagots was upset and smashed by the waters, which flowed from 

 all the cultivated slopes, and tore along, with the noise of thunder, at the bottom of 

 the ravine. 



My good fortune secured to me another subject of study on the same ground. 



On the 25th of October following I wont to the sale of the fellings of the Tarascon, 

 where there fell an abundant rain. The next day, the 26th, the weather was clouded. 

 I set off for the Luberon in the hope of arriving there at the same time as would a 

 storm of rain, which I saw approaching. I arrived first; the ravine of Saint-Phalez 

 was still moist from the passage in small quantity of the waters of the night before : 

 they had served, as appeared, to saturate the lands of the domain, as had previously 

 happened on the 7th (3d?) of September, 



11 A — '84 



