EVILS FOLLOWING DESTRUCTION OF FORESTS. Si 



upon which the rain falls are devoid of vegetation, the 

 rain rushes off as does water on the roof of a house and 

 thus was it here. 



The Journal des Debats thus explains the phenomena of 

 these inundations : 



' It is the chain of the Cevennes which causes these 

 immense disorders. Between the sources of the Loire 

 and the Herault the Cevennes are 3,700 feet high. All 

 this surface is composed of granite impermeable to the 

 rains. The river waters rash over this ground with 

 immense rapidity, but do not enter it. The chief streams 

 rising there are the Dour, the Ervieux, the Ardeche, and 

 the Gardon, affluents of the Rhone j on the west, the Lot 

 and the Tarn, affluents of the Garonne ; on the north, the 

 Loire and its tributary the Allier ; on the south, the 

 Herault. The Ardeche, whose basin is only 2,492 kilo- 

 metres, has enormous rises. At the bridge d'Arc the 

 stream rises to nineteen metres above the lowest level, 

 and pours down at a rate of 7000 cubic metres per second, 

 almost as much as the Loire at Tours. An equal violence 

 is registered in the Dour, the Ervieux, the Gardon, the 

 Isere, the Drome, and the Durance. Since everything 

 depends on the rainfall, it is obviously impossible to 

 calculate with certainty beforehand. Every year the 

 Cevennes cause vast " spates " in the largest rivers in 

 France the Rhone, the Loire, and the Garonne. All the 

 streams of the regions are torrents. The southern part of 

 the Cevennes, the Black Mountain, and the Corbi&res 

 exercise a great influence on the small Mediterranean 

 streams between the Rhone and the Pyrenees. A rain of 

 200 millimetres, which has no perceptible effect elsewhere, 

 causes in these parts a sudden flood/ 



In general the rains fall there in May, and being then 

 comparatively cool, they melt but little of the snow, and 

 flow away as they fall. But when they fall in June, as 

 this year they did, they are somewhat tepid, and falling 

 upon the snow, melt it rapidly, and the watery produce is 

 added to the rainfall ; thus two sources of flood are com- 



G 



