86 M. Boussingault vn the Effect of' clearing Land 



falls than formerly. This, in truth, is the opinion which most 

 generally prevails upon the point ; and if admitted without fur- 

 ther examination, we must necessarily yield to the conclusion 

 that the clearing away of the forests diminishes the annual quan- 

 tity of the rain which falls upon the district. But on the other 

 hand, even allowing that all the circumstances alluded to have 

 been satisfactorily ascertained, still it has also been observed, 

 that since the clearing of the mountains, the different torrents 

 and rivers which seem to have lost a portion of their waters, oc- 

 casionally manifest such sudden and extraordinary rises, that 

 extensive devastations are the frequent consequence. It has 

 likewise been observed, that after great falls of rain the springs 

 which had almost entirely disappeared, suddenly rise with un- 

 usual impetuosity, only to subside with corresponding rapidity. 

 The natural inference from these latter observations, as will be 

 at once perceived, is, that we are not too readily to adopt the 

 common opinion, and to admit that the cutting down of the 

 woods diminishes the annual fall of rain : for it may not be at 

 all impossible, not only that the actual quantity of rain has 

 not varied, but that the quantity of water passing off in the 

 running streams may be really the same, in spite of the appa- 

 rent drought at certain periods of the yeai-, both in the rivers 

 and the springs ; and possibly the only difference will turn out 

 to be, that the flowing of the same mass of water has, owing to 

 the clearing, become much more irregular. In illustration, we 

 may remark, that if the small quantity of water which is found 

 in the Rhone, dui-ing a certain part of the year, was precisely 

 compensated by a sufficient number of great floods, the neces- 

 sary consequence would be, that it still conveys to the Me- 

 diterranean the same volume of water which it did, at the 

 epoch anterior to the extensive clearings which have been ef- 

 fected near its principal sources, and when, probably, its mean 

 depth was not, as it now is, subject to great variations. If this 

 were actually the case, the existence of the forests would be at- 

 tended with this advantage, that they would in some degree 

 regulate and equalize the flow of the water. But if, on the other 

 hand, the whole annual quantity of the flowing water becomes 

 less as the clearing away of the forests extends, then the effect 

 must be attributed either to the rains becoming less abundant, 



