Many are overtaken in the mad flight and perish. The fierce fires
of this type can be stopped only by heavy rain, a change of wind,
or by barriers which provide no fuel and thus choke out the
flames.

Large fires are sometimes controlled by back-firing. A back-fire
is a second fire built and so directed as to run against the wind
and toward the main fire. When the two fires meet, both will go
out on account of lack of fuel. When properly used by experienced
persons, back-fires are very effectual. In inexperienced hands
they are dangerous, as the wind may change suddenly or they may
be lighted too soon. In such cases they often become as great a
menace as the main fire. Another practical system of fighting
fires is to make fire lines around the burning area. These fire
lines or lanes as they are sometimes called, are stretches of
land from which all trees and shrubs have been removed. In the
centre of the lines a narrow trench is dug to mineral soil or the
lines are plowed or burned over so that they are bare of fuel.
Such lines also are of value around woods and grain fields to
keep the fire out. They are commonly used along railroad tracks
where locomotive sparks are a constant source of fire dangers.

Our forests, on account of their great size and the relatively
small man force which guards them, are more exposed to fire
dangers than any other woodlands in the world. The scant rainfall
of many of the western states where great unbroken areas of
forest are located increases the fire damages. The fact that the
western country in many sections is sparsely settled favors
destruction by forest fires. The prevalence of lightning in the
mountains during the summer adds farther to the danger. One of