194 STUDIES OF TREES 



and property; see Fig. 132. From ten to twelve million 

 acres of forest-land are burnt over annually and the timber 

 destroyed is estimated at fifty millions of dollars. The 

 history of Forestry aljounds in tales of destructive fires, 

 where thousands of persons have been killed or left desti- 

 tute, whole towns wiped out, and millions of dollars in 

 property destroyed. In most cases, these uncontrollable 

 fires started from small conflagrations that could readily, 

 with proper fire-patrol, have been put out. 



There are various ways of fighting fires, depending on 

 the character of the fire, — whether it is a surface fire, burning 

 along the surface layer of dry leaves and small ground 

 vegetation, a ground fire, burning below the surface, through 

 the layer of soil and vegetable matter that generally lines 

 the forest floor, or a top fire, burning high up in the trees. 



When the fire runs along the surface only, the injury 

 extends to the butts of the trees and to the young seedlings. 

 Such fires can be put out by throwing dirt or sand over the 

 fire, by beating it, and, sometimes, by merely raking the 

 leaves away. 



Ground fires destroy the vegetable mold which the trees 

 need for their sustenance. They progress slowly and kill 

 or weaken the roots of the trees. 



Top fires. Fig. 133, are the most dangerous, destroying 

 everything in their way. They generally develop from 

 surface fires, though sometimes they are started by lightning. 

 They are more common in coniferous forests, because the 

 leaves of hardwoods do not burn so readily. Checking 

 the progress of a top fire is a difficult matter. Some fires 

 will travel as rapidly as five miles an hour, and the heat 

 is terrific. The only salvation for the forest lies, in many 

 cases, in a sudden downpour of rain, a change of wind, or 

 some barrier which the fire cannot pass. A barrier of this 



