298 liOCAL EFFECTS OF FORESTS 



days. The only efifeot of this was that, on the evening of the 30th, 

 near the forester's house, and at 200 or 300 mfetres from the ravine 

 of Saint-Phalez, there was seen coming down, in that of Yeuse, a 

 small fillet of clear water ; its volume increased perceptibly during 

 three days, to diminish in like manner during the two which followed; 

 its passage broke down a little of the foot-path which goes along the 

 valley, but caused only a damage easily repaired. This foot-path did 

 not present the same solidity of structure as that of the Combe de 

 Saint-Phalez, built on enormous blocks of rook which had stood for 

 several years, and which had allowed of passage with a waggon some 

 days before its destruction by the storm in September. If the 

 Combe-d'Yeuse had yielded as much water as that of Phalez, and if 

 these two masses of water had come at the same time, the damage 

 caused in the plain would have been considerable, and the Durance, 

 which received these waters, would have been so much the larger. 



" Thus we have two torrents very near and under the same condi- 

 tions — except that the basin drained by the one comprises 50 hectares 

 of cultivated lands, that of the other 250 hectares of woodlands. The 

 first receives, and allows to flow away, the waters of the greater part 

 of a storm in a few hours at most, causing thereby considerable 

 damage ; the second, which had received a greater quantity of rain, 

 stores it — ^k^eps it for two days — evidently retaining a portion of it, 

 and takes three or four days to yield up the surplus, which it does in 

 the form of a limpid and inoffensive stream." 



A question iu connection with this subject, which excites much 

 general interest, is — Do woods and forests increase the quantity of 

 the rainfall ? We have had testimony to the affect that in certain 

 conditions they increase the quantity of the local rainftill ; there is 

 no evidence that in consequence of this there is a diminished rainfall 

 elsewhere, and if there be not it follows as a consequence that they 

 do increase the rainfall, though it should be found that they do so 

 only by causing the same material to fall again and again in the form 

 of rain; but the increase, whether tested by local observations care- 

 fully conducted as were those of Mathieu, and of which have beea 

 cited, [ante p. 64] or by more general observations carefully collected 

 as were those discussed by Mr Draper, [ante p. 100] appears to be very 

 trifling ; and when there are brought under consideration such features 

 of physical geography as are referred to by C6zanne and by Costa de 

 ^astelica, and attributed to torrents occasioned by the rainfall previous 

 to the rigime of forests in the locality, it may well be doubted whether 



