25 



CHAPTEE II. 



INDIRECT UTILITY OF FORESTS. 



A PIECE of land l)are of vegetation is, throughout the year, 

 exposed to the full effects of the sun and air currents and 

 the climatic conditions which are produced hy these agencies. 

 If, on the other hand, a piece of land is covered with a 

 growth of plants and especially with a dense crop of forest 

 vegetation, it enjoys the benefit of certain agencies which 

 modify the effect of sun and wind on the soil and the 

 adjoining layers of air. These modifj'ing agencies may be 

 shortly enumerated as follows : — 



(1.) The crowns of a full crop of trees provide a more or 

 less dense roof at a certain distance from the ground which 

 intercepts the rays of the sun and the falling rain, obstructs 

 the movement of air currents and reduces radiation of heat 

 during the night. 



(2.) The leaves, flowers and fruits, augmented by certain 

 plants which grow in the shade of trees, form a layer of 

 organic matter, or humus, which protects the soil against 

 changes of temperature and greatly influences the movement 

 of water and air in the soil. 



(3.) The roots of the trees penetrate into the soil in all 

 directions and bind it together, or loosen it. 



The effects of these agencies have been observed and 

 recorded from ancient times down to the present, and 

 hundreds of pages could be filled with the record of instances 

 in which forest vegetation has affected, or has been believed 

 to have affected, the climate, the rainfall, the regulation of 

 moisture, the stability of the soil, the healthiness of countries 

 and allied matters ; if quantity of evidence alone were wanted, 

 tlie case might l»e considered as " proven." In all such 



