302 The Farm Woodlot 



leaven of truth in it all, and the present beliefs, wild as 

 they seem, are nearer the facts than no belief at all. 



INFLUENCE ON PRECIPITATION 



The most generally mooted question of to-day is whether 

 the forest is the direct cause of greater rainfall, whether 

 the precipitation is greater in the forest than in the open 

 country; and if so, how much greater. Belief in such 

 influence is used as an argument in favor of planting trees, 

 and has considerable weight with many. In spite of its 

 prominent place in the public mind, this is probably the 

 least important of the forest influences. Competent 

 scientific men have been studying this question in Euro- 

 pean countries for a century or more, where there are vast 

 forests of very dense growth, but they have not as yet 

 been able to decide definitely whether that particular in- 

 fluence exists or not. If, then, this influence, increase in 

 rainfall, is so small as to be imperceptible in the case of an 

 extensive and dense forest, it certainly need not interfere 

 with our calculations in the consideration of a small plan- 

 tation of a few acres. This factor may be wholly disre- 

 garded in all farm forestry. A forest, then, does not in- 

 fluence the amount of precipitation, but it does have an 

 important influence on the disposal of the precipitation. 

 This, in fact, is one of the most important effects of forest 

 cover. It directly controls the permanent flow of springs 

 and streams. 



INFLUENCE ON RUN-OFF. Fig. 60 



The influence of forest cover on surface run-off was noted 

 long ago in other countries and has been forced upon the 



