The line of demarcation between the burned and the unburned areas seemed extraordinarily well defined. Bob looked closer and saw that this definition was due to a peculiar path, perhaps two yards wide. It looked as though some one had gone along there with a huge broom, sweeping as one would sweep a path in deep dust. Only in this case the broom must have been a powerful implement as well as one of wide reach. The brushed marks went not only through the carpet of pine needles, but through the tarweed, the snow brush, the manzañita. This was technically the fire line. At the sight of the positiveness with which it had checked the spread of the flames, Bob's spirits rose.
"They seem to have stopped it here easy enough, already," he cried.
"Being as how this is the windward side of the fire, and on a down slope, I should think they might," remarked Jack Pollock drily.
Bob chuckled and glanced at the girl.
"I'm finding out every day how little I know," said he; "at my age, too!"
"The hard work is down wind," said Amy.
"Of course."
They entered the burned area, and climbed on up the hill. Though evidently here the ferocity of the conflagration had passed, it had left its rear guard behind. Fallen trees still blazed; standing trees flamed like torches—but all harmlessly within the magic circle drawn by the desperate quick work of the rangers. They threaded their way cautiously among these isolated fires, watching lest some dead giant should fall across their path. The ground smoked under their feet. Against the background of a faint and distant roaring, which now made itself evident, the immediate surroundings seemed very quiet. The individual cracklings of flames were an undertone. Only once in a while a dull heavy crash smote the air as some great tree gave up the unequal struggle.
They passed as rapidly as they could through this stricken field. The night had fallen, but the forest was still bright, the trail still plain. They followed it for an hour until it had topped the lower ridge.
Then far ahead, down through the dark trunks of trees, they saw, wavering, flickering, leaping and dying, a line of fire. In some places it was a dozen feet high; in others it sank to within a few inches of the ground—but nowhere could the eye discern an opening through it. A roar and a crackling filled the air. Sparks were shooting upward in the suction. A blast of heat rushed against Bob's cheek. All at once he realized that a forest fire was not a widespread general conflagration, like the burning of a city block. It was a line of battle, a ring of flame advancing steadily. All they had passed had been negligible. Here was the true enemy, now charging rapidly through the dry, inflammable low growth, now creeping stealthily in the needles and among the rocks; always making way, always gathering itself for one of its wild leaps which should lay an entire new province under its ravaging. Somewhere on the other side of that ring of fire were four men. They were trying to cut a lane over which the fire could not leap.