66 MODERN FOREST ECONOMY. 



special attention to the subject, of the mean rise of a 

 number of rivers in the same district being twenty-eight 

 feet ; I have been told by the same gentleman of a maxi- 

 mum rise of sixty feet ; and I have gone over the scene of 

 devastation occasioned by the sudden rise of a river to a 

 height of seventy feet above its usual level.' 



It was in the basin of the Gamptoos, at Hankey. In 

 the volume already cited, Eeboisement in France (pp. 335- 

 339), I have given details of the inundation which it 

 occasioned, and of the consequent destruction of life and 

 property; and in the volume entitled Hydrology of South 

 Ajrica (pp. 229-247), I have given details of several of the 

 floods and inundations previously mentioned {ante p. 55]. 



There are cases on record of great sudden falls of rain, 

 such as on previous occasions, when the basin of reception 

 was devoid of trees, had given rise to floods of a threaten- 

 ing and destructive character occurring after thsit basin 

 had been replanted, being carried slowly away without 

 damage or danger to life or property; and a broad 

 girdle of trees on a mountain side has sufficed to arrest the 

 flow and coalescence of streamlets rushing from the sum- 

 mit after a heavy rainfall or a sudden thaw. 



Of such and such-like phenomena many cases are 

 embodied in the volume I have cited, Eeboisement in 

 France. 



An inundation is simply a flood of such magnitude that 

 the surface surmounting the banks of the river bed, it 

 flows over and spreads upon the land beyond. Most 

 floods may be attributed to heavy and long-continued 

 rains, or to the melting of great quantities of snow. 

 Forests both arrest and retard the flow of the rainfall, 

 and retard the melting of snow, and the flow of the 

 produce, and thus it is that they prevent inundations. 

 The inundation in France which we have had under con- 

 sideration was attributed to the simultaneous occurrence of 

 continuous heavy rains and a sudden melting of snow on 

 the mountains, both of them incidents of annual occur- 



