of 



Birds work for us all the time, and board them- 

 selves most of the time. Birds are of inestimable 

 value to agriculture, but many of these useful 

 species need forest shelter. So to lose a forest 

 means at the same time to lose the service of 

 these birds. 



The forest is a sanitary agent. It is constantly 

 eliminating impurities from the earth and the 

 air. Trees check, sweep, and filter from the air 

 quantities of filthy, germ-laden dust. Their 

 leaves absorb the poisonous gases from the air. 

 Roots assist in drainage, and absorb impurities 

 from the soil. Roots also give off acids, and 

 these acids, together with the acids released by 

 the fallen, decaying leaves, have a sterilizing 

 effect upon the soil. Trees help to keep the earth 

 sweet and clean, and water which comes from a 

 forested watershed is likely to be pure. Many 

 unsanitary areas have been redeemed and ren- 

 dered healthy by tree-planting. 



Numerous are the products and the influences 

 of the trees. Many medicines for the sick-room 

 are compounded wholly or in part from the 

 bark, the fruit, the juices, or the leaves of trees. 



133 



