EVILS FOLLOWING DESTRUCTION OF FORESTS. 67 



rence, but at times some days or weeks apart. The best 

 preventitive of the catastrophe would have been the 

 reboisement of the mountains ; but the action of the woods 

 and forests on plains, or what pass as plains, is the same. 



In a paper on this subject, read at a meeting of the 

 Societe d' Agriculture de la Haute- Garronne on the 26th 

 July 1877, by M. De Gorsse, it is stated : ' An inundation 

 may be attributable as a matter of fact to two different 

 causes ; it may be occasioned by an extraordinary flood of 

 very short duration, the consequence of a violent storm, 

 of a long continuance of rain, or of a sudden melting of 

 snow ; or it may be occasioned by the progressive filling 

 up of a river bed by the deposit of material torn away 

 from the sides of mountains which are furrowed by them. 

 These causes may act separately, but most frequently they 

 are combined. In both cases the duration of the flood is 

 the decisive co-efficient of the inundation; for supposing 

 it were protracted, the flow of the same quantity of water 

 being effected gradually, the overflowing of 'the banks 

 would be averted. When a single second suffices for the 

 delivery of many thousand cubic metres of water can it 

 be surprising that a gain of some hours for the delivery 

 may at times save a country from a most dreadful 

 scourge? It is then evident that all circumstances which 

 tend to protract the flow diminish the danger, whilst 

 those which concur to diminish the time of the duration 

 of the flood aggravate the peril. 



' Now the action of forests in retarding the flow is very 

 powerful if a storm or a continuance of rains fall upon a 

 wooded slope, [and the effect will be esentially the same 

 on a comparative plain] ; a great quantity of the rainfall 

 will from the first be arrested by the foliage and by the 

 branches of the trees, which will subsequently restore it 

 to the atmosphere, or transmit it to the ground, according 

 as rise of temperature supervening in this air, now satu- 

 rated with moisture, may permit evaporation to resume 

 activity, or as the agitation of the air shall determine the 



