PROTECTION OF FORESTS FROM FIRE 305 



front attack. Sometimes, by this plan, the front may be 

 rapidly narrowed by working from the sides, until it is at 

 last entirely extinguished. The plan of giving direction 

 to the course of the fire has often been successfully carried 

 out when the fighting crew is too small for a direct attack. 



Methods of Fighting Ground Fires. — Ground fires, 

 burning in the deep layer of organic matter, are exceed- 

 ingly difficult to extinguish. If the layer of vegetable 

 matter is not verv deep, it is sometimes possible to put 

 out the flames bv water or sand. If the layer is deep, 

 trenching is the only practical method of stopping the 

 progress of the fire. In using this method of fighting 

 ground fires, one judges the rapidity with which the fire 

 is burning and then, at a proper distance away, digs a 

 trench through the vegetable layer down to the mineral 

 soil, using axes, mattocks, and shovels, as the particular 

 case may require. Such a trench, which has a width at 

 the bottom of 1 foot, will enable the fighters to stop an 

 ordinary ground fire, especiallv if the work can be sup- 

 plemented by the use of water or sand at the trench. 



Methods of Fighting Crown Fires. — Crown fires are 

 always accompanied by surface fires. Crown fires stop 

 when there are no longer inflammable crowns through 

 which the fire will run, or when there is no longer any 

 material on the ground to carry the surface fire. An 

 ordinary crown fire will jump a wide fire-line, and many 

 fires have been known to cross wide rivers, almost with- 

 out check. In the mountains, a crown fire running up a 

 slope is almost impossible to check. 



