MISCELLANEOUS 28 1 



affected by trees. Examine some wood mold, as we call the soil 

 of the forest. It is loose and damp, made up of decayed and 

 decaying leaves and twigs. The wood mold and tree roots form a 

 vast sponge to catch and hold the rainfall. They give it out gradu- 

 ally and regularly by capillarity and evaporation and through 

 streams. They protect the land against surface washing and, to 

 a great extent, against loss of water by evaporation. 



With the wood mold compare the hard compact earth on a 

 barren hillside. Instead of sinking in this, much water runs off, 

 leaving it hard and dry. It is subject to floods and to droughts 

 which affect the forest but little. 



If you consult a map of the United States, you find that the head 

 waters of its great rivers are in the mountains. Nature has cov- 

 ered the mountain sides with forests, which store up floods and 

 supply the waters gradually to the streams. What will happen 

 if these forests be cut? The mountains will be changed from 

 reservoirs to mere watersheds. Down their steep slopes floods 

 will rush to the valleys and plains below, destroying and bearing 

 away crops, plantations, villages. 



More than one third of the seaward-going water of the United 

 States makes its way through the Mississippi. How important it 

 is to have forest reservoirs on its head waters, and to use and dis- 

 tribute the water along its course as evenly as possible ! If this be 

 not done, the fertile valley will finally be destroyed. It has been 

 neglected so far, and every year the levees are piled higher, every 

 year the flood-mark rises. 



It is necessary to preserve forests not only to regulate the flow of 

 streams, but to give a regular supply of water for irrigation. Irri- 

 gation is needed in nearly one third of the United States. Without 

 forests, it is impossible. 



National Forests. Since 1891 the United States government 



