CLIMATE AS INFLUENCED BY THE FOREST. 133 



referring to the manner in which man may influ- 

 ence the climate of any particular part of the 

 earth, says on page 471 : 



" Human interference affects meteorological conditions : 1, 

 by removing forests and laying bare to the sun and winds 

 areas which were previously kept cool and damp under trees, 

 or which, lying on the lee side, were protected from tempests ; 

 as already stated, it is supposed that the wholesale destruction 

 of the woodlands formerly existing in countries bordering the 

 Mediterranean has been in part the cause of the present desic- 

 cation of these districts; 2, by drainage, the effect of this 

 operation being to remove rapidly the discharged rainfall, to 

 raise the temperature of the soil, to lessen the evaporation, and 

 thereby to diminish the rainfall and somewhat increase the 

 general temperature of a country ; 3, by the other processes 

 of agriculture, such as the transformation of moor and bog 

 into cultivated land, and the clothing of bare hill-sides with 

 green crops or plantations of coniferous and hard-wood trees." 



Not only does the forest prevent the excessive 

 heating of the land on which it grows, and there- 

 fore similar excessive heating of the air over the 

 land, by the greatly extended surface the trees and 

 undergrowth present to the sun's rays, but it also 

 acts by the direct absorption of the sun's rays 

 to cause the separation of the carbon from the 

 oxygen in carbonic acid, and the hydrogen from 



the oxygen in the water in the vegetable king- 



12 



