THE FOREST AS A CONDITION. 75 



the more even riverflow. While the waters that 

 run off over the surface collect rapidly and are car- 

 ried away in floods, giving rise to high water stages, 

 the percolated water finds its way into the river 

 slowly by underground channels, feeding, on its 

 way, springs and brooks, or is collected as ground 

 water by seepage at lower levels. 



This distribution of the water, which lengthens 

 the time during which the atmospheric precipita- 

 tion can be usefully employed, and which, under 

 circumstances, may lengthen the supply for years, 

 the water reaching the river years after it fell on 

 the mountain top, renders the riverflow indepen- 

 dent of wet and dry seasons, and equalizes its 

 flow, a condition of most importance for all in- 

 dustries dependent on water-power, navigation, irri- 

 gation, etc. 



This forest effect on the run-off of terrestrial 

 waters is naturally greatest and most important in 

 mountainous regions, where the water has the 

 tendency to collect quickly and to be carried off 

 rapidly, but it also exists in the level plain, where 

 it has the tendency to elevate the general ground- 

 water level and thereby make a reserve available 

 during times of drouth. 



In close connection with these effects of forest 

 cover upon the flow of water stands its influence 

 on the stability of the soil. The tendency of the 

 rain waters falling on hills and mountains is to carry 

 in their descent to the valley loose particles of soil 



