78 



A PKIMER OF FORl^:STRY. 



There is danger from forest fires in the dry portions 

 of the spring- and summer, but those which do most 

 harm usually occur in the fall. At whatever time of 

 the year they appear, their destructive power dej^ends 

 very much on the wind. They can not travel against 

 it except when burning up hill, and not even then if 

 the wind is strong. The wind may give them strength 



Fig. 73.— a clearing in Spruce timber. The great cost and difficulty of such 

 clearing is well illustrated. In the foreground is a tield of potatoes. Olympic 

 Forest Keserve, Washiugton. 



and speed by driving them swiftly through unburned, 

 inflammable forests, or it may extinguish the liercest 

 fire in a short time by turning it back over its path, 

 where there is nothing left to burn. In fighting forest 

 fires the wind is always the first thing to consider, and 

 its direction must be carefully watched. A sudden 



