16 FOREST POLICY. 



3. The litter and debris on the ground act as a sponge and cause 

 precipitations to trickle through gradually. 



4. The melting of the snow is retarded under a dense forest 

 cover. 



5. The evaporation from the soil in summer is reduced. 



The points I, 2 and 3 change rapid surface drainage into slow 

 underground drainage. 



On the other hand, as stated in the preceeding paragraph, trees 

 lower the level of the ground water. 



Afiforestation in the European Alps proves conclusively that 

 there is an influence of the forests on the regularity of stream flow. 



The fact that inundations are now more frequent in this country 

 than they were twenty years ago must be explained, to a high degree, 

 by river courses cleaned for the benefit of navigation, by bottom 

 land cleared and by swamps drained for the benefit of agriculture. 



Agriculture is certainly more responsible for the destruc- 

 tion of its own crops in the lowlands^ by freshets and inundations, 

 than destructive forestry in the mountains. Here, after Dr. C. A. 

 Schenck, the man who burns the litter on the ground is to blame, and 

 not the lumbermen who cut the trees; for it is the litter on the 

 ground — more than the tree — that regulates the flow of our moun- 

 taiti streams. 



(XXI.) MECHANICAL INFLUENCE OF THE FOREST. 



The mechanical influence of the forest is shown by the prevention 

 of excessive erosion on forest-covered slopes. Previous to afforesta- 

 tion of gullied slopes, breastworks should be made beginning at the 

 upper edge of the gullies. When the soil is quieted down, planting 

 may begin. 



Forest plantations may also be used to prevent the inland move- 

 ment of sand dunes along the seashore. Dunes must be first fixed 

 and raised as high as possible by planting sand grasses on the leeward 

 side; afforestation (with pines) may set in thereafter. 



Forests are also recommended as remedies for avalanches. The 

 formation of avalanches must be prevented at the " point of rupture." 

 This point, however, lies frequently above timber line. Stone walls 

 are certainly more efficient at such points than plantations of trees. 

 Forests further offer protection against air currents. In the prairies, 

 shelter belts of forests prevent blizzards from laying wheat lands 

 bare of snow and facilitate the wintering of 'stock. 



The influence of the forest on hail storms is limited, perhaps 

 imaginary. 



(XXIL) DIRECT UTILITY OF THE FOREST. 



The variety of raw products furnished by the forests is very con- 

 siderable. We may distinguish between " principal products " and 



