PARAGRAPH XXI. 



MECHANICAL INFLUENCE OF THE FOREST. 



The mechanical influence of the forest is shown by the pre- 

 vention of excessive erosion on forest-covered slopes. Successful 

 afforestation puts a stop to local erosion. Previous to the af- 

 forestation of gullied slopes, breastworks should be made be- 

 ginning 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 

 movement of sand dunes along the seashore. To begin with, 

 the dunes must be fixed and raised with the help of rough 

 fences, sandgrasses, sandweeds etc. That done, afforestation may 

 begin on the leeward side of the dunes, or in the dales between 

 the dunes. 



Forests are also recommended as remedies for avalanches. The 

 formation of avalanches must be prevented at the "point of 

 rupture." This point, however, lies above timber line frequently. 

 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 trees prevent the blizzards from laying 

 the wheat lands bare of snow. The existence of a wood lot 

 facilitates the wintering of cattle, sheep, and hogs. 



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

 imaginar}'. 



