296 LOCAL EFFECTS OF FORESTS 



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

 the summit, where are some hundred metres 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 kilometres. It is 

 strongly embanked, surmounted by steep declines, 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, pi-ecipitately inclined, with a general 

 southwest 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 storms or great rains, and this water 

 soon passes away, with the differences which will afterwards be men- 

 tioned. 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 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 southwest wind struck on the Lnberon. Its passage 

 did not last more than forty minutes ; but scarcely had it come when 

 the torrent of Saint Phalez became awful. Its maximum delivery 

 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"*. Each square metre had received 40 litres, and the 50 hectares 

 of Saiut-Phalez 20,000 cubic metres. The ground had only retained 

 5000, which is sufficiently explained by their argillaceous character 

 and their state of saturation the night before. But while the 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'Yeuse and all 

 those traversing wooded lands remained dry, or gave only an insignifi- 

 cant quantity of water. 



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

 the valley of the Peyne, a carriage-road newly formed did not ex- 



