rong side of the line? If it happens when none of us are
around, why the fire gets a start. And maybe a coal will roll down hill
from somewhere; or a breeze come up and carry sparks. One spark over
here," he stamped his foot on the brushed line, "and it's all to do over
again. There's six of us," added the ranger, "and a hundred of these
trees near the line. By rights there ought to be a man camped down near
every one of them."

"Give us our orders," repeated Bob.

"The orders are to patrol the fire line," said Morton. "If you find the
fire has broken across, corral it. If it gets too strong for you, shoot
your six-shooter twice. Keep a-moving, but take it easy and save
yourself for to-morrow. About two o'clock, or so, I'll shoot three
times. Then you can come to camp and get a little sleep. You got to be
in shape for to-morrow."

"Why especially to-morrow?" asked Bob.

"Fire dies in the cool of night; it comes up in the middle of the day,"
explained Morton succinctly.

Bob took to the right, while Jack went in the opposite direction. His
way led down hill. He crossed a ravine, surmounted a little ridge. Now
he was in the worse than total darkness of the almost extinct area.
Embers and coals burned all over the side hill like so many evil winking
eyes. Far ahead, down the mountain, the rising smoke glowed incandescent
with the light of an invisible fire beneath, Bob, blinded by this glow,
had great difficulty in making his way. Once he found that he had
somehow crept out on the great bald roundness of a granite dome, and had
to retrace his steps. Twice he lost his footing utterly, but fortunately
fell but a short distance. At last he found himself in the V of a narrow
ravine.

All this time he had, with one exception, kept close track of the fire
line. The exception was when he strayed out over the dome; but that was
natural, for the dome had been adopted bodily as part of the system of
defence. Everywhere the edge of the path proved to be black and dead. No
living fire glowed within striking distance of the inflammable material
on the hither side the path.

But here, in the bottom of the ravine, a single coal had lodged, and had
already started into flame the dry small brush. It had fallen originally
from an oak fully a hundred feet away; and in some mysterious manner had
found a path to this hidden pocket. The circumstances somewhat shook
Bob's faith in the apparent safety of the country he had just traversed.