INFLUENCE OF THE FOEEST ON FLOODS. 227 



dence on the subject may be, that, under ordinary circumstances, 

 the process of conversion of bare ground to soil with a well- 

 wooded surface is so gradual and slow, and the time required for 

 a fair experiment is consequently so long, that many changes 

 produced by the action of the new geographical clement escape 

 the notice and the memory of ordinary observers. The growth 

 of a forest, including the formation of a thick stratum of vegetar 

 ble mould beneath it, is the work of a generation, its destruction 

 may be accomplished in a day ; and hence, while the results of 

 the one process may for a considerable time be doubtful, if not 

 imperceptible, those of the other are immediate and readily ap- 

 preciable. Fortmiately, the plantation of a wood produces other 

 beneficial consequences which are both sooner reahzed and more 

 easily estimated ; and though he who drops the seed is sowing 

 for a future generation as well as for his own, the planter of a 

 grove may hope himself to reap a fair return for his expenditure 

 and his labor. 



Influence of the Forest on Inundations and Torrents. 



Inasmuch as it is not yet proved that the forests augment or 

 diminish the precipitation in the regions they principally cover, 

 we can not positively aflirm that their presence or absence in- 

 creases or lessens the total volume of the water annually dehvered 

 by great rivers or by mountain torrents. It is nevertheless certain 

 that they exercise an action on the discharge of the water of rain 

 and snow into the valleys, ravines and other depressions of the 

 surface, where it is gathered into brooks and finally larger cur- 

 rents, and consequently they must influence the character of floods, 

 both in rivers and in torrents. For this reason, river inundations 

 and the devastations of torrents, and the geographical effects re- 

 sulting from them, so far as they are occasioned or modified by 

 the action of forests or of the destruction of the woods, may 

 properly be discussed in this chapter, though they might seem 

 otherwise to belong more appropriately to another division of this 

 work. 



them. On bare soils he has created, at more than a hundred jKtints, forests 

 and watercourses." Inquiring, however, of intelligent persons long resident 

 in Australia, I find no confirmation of this statement. 



