HOW THE FOREST IS GUARDED 97 
flames themselves creates a draft and sends firebrands 
and blazing bits of bark whirling ahead many rods to 
set new fires ahead of the advancing front. Close 
approach to the fire is out of the question, and only by 
clearing a wide strip far ahead of the fire and “back 
firing’ can the crown fires be stopped. The idea in back 
firing is to start a small fire on the edge of a cleared 
strip which is permitted and encouraged to burn against 
the wind toward the advancing blaze. The fire line, of 
course, is carefully guarded by a Lne of men to prevent 
this fire from leaping over it and burning the timber 
it is desired to save. As the back fire burns, of course, 
it consumes all brush and inflammable material and 
leaves nothing for the main fire to feed upcn, As the 
two fires approach a terrific draft is created and the 
two flames rush to meet each other with a loud roar and 
after burning fiercely for a time, gradually die out. The 
front of the fire having been disposed of, the ground 
fire left burning is then taken care of. In some cases 
where a crown fire has assumed large proportions owing 
to high winds and long drought, human aid is futile; 
only rain or a change in wind to drive the flames back 
upon the burned-over area can quench the blaze. 
Fighting a ground or surface fire, while laborious, 
is not so dangerous, as tne fire makes headway slowly. 
Different methods of fighting are used depending on the 
ground cover, soil, topography, and water supply. In 
the Adirondacks a ground fire must be fought by cutting 
a trench around it, as the deep layer of humus burns 
like peat. In rocky soil dynamite may be used to dig 
this trench far better than men with mattocks and 
shovels. In case of a surface fire where only the light 
litter is burning, a cedar brush or wet burlap bag 
may be used to beat out the fire, but care must be taken 
