64 



A PRIMER OF FORESTRY. 



air of the forest has less capacity for taking up water 

 vapor than that of the open countoy. It is also qui- 

 eter, which means that the winds are less active in 

 replacing saturated air with air which can still take up 

 more water. The forest acts powerfully in checking 

 the force of the winds because the elastic swaying of 

 the twigs and branches is a very effective hindrance to 



FIG. 41. A windbreak. California. 



the movement of the air. Strong winds, although they 

 are often dangerous in themselves, do most harm by 

 drying up the moisture in the soil and in the plants 

 which grow from it. Thousands of miles of wind- 

 breaks have been planted by farmers in the western 

 parts of this country to protect their crops and homes 

 against the wind. These windbreaks serve a most use- 

 ful purpose, but they are naturally far less effective in 



