EFFECT OF FORESTS ON MOISTURE. 15 



these results, because the two stations are not placed at the same 

 elevation, and they are too far apart with the town of Nancy to 

 some extent between them. 



Other evidence is available of which the following may be 

 mentioned : — 



(1) Ebermayer's observations in Bavaria, started in 1867 and 



carried out with great care, do not justify any final con- 

 clusion as to an increase of the rainfall due to the action of 

 forests. He states that in the plains the effect of forests 

 is certainly very small, but that it increases with elevation. 



(2) Extensive observations made in Sweden, on 400 stations 



during a period of 15 years, show that the difference 

 between parts of the country with 56 per cent, of the land 

 under forest and those with only 17 per cent, under forest 

 is certainly not more than 3 per cent, increase in favour 

 of the former. 



(3) The Government of India has during late years investigated 



the subject, and the results obtained do not justify any 

 direct conclusions beyond the fact that, if forests influence 

 the rainfall at all, the effect is insignificant. 



To sum up it may be said that various physical factors act 

 towards rendering forests condensers of vapour ; this faculty is 

 more evident in elevated positions than in low lands and in the 

 vicinity of the sea, where it is swamped by other more powerful 

 agencies. Certainty about these phenomena can be obtained only 

 through further extensive observations. 



In connection with this subject it should be mentioned that a 

 forest crop prevents a portion of the rainfall from reaching the 

 ground, because it is intercepted by the crowns of the trees. Light 

 showers may be altogether intercepted, and the water may 

 evaporate before any part of it reaches the ground. In the case 

 of heavy showers or continued rain, a considerable part of the 

 intercepted w^ater will run down the branches and stem. Accord- 

 ing to observations, the average loss has been estimated at about 

 ^ of the total rainfall, though the actual amount depends on the 

 total ramfall and the species of trees. 



The question whether forests reduce the formation of hail has 

 been much discussed. Investigations show that the effect is very 

 small, if it exists at all. 



