The chums swiftly retraced their steps to where the animals waited patiently, removing the packs and sending the little donkeys down the trail to better pasturage. They might wander, but they would be safe. With their swift heels they could defend themselves from even a mountain lion. And they were apt to keep to the mountain meadows, where was food and water.

Their run at such an altitude had given Pedro a touch of mountain sickness, and he had to lie flat till his heart beat more normally and his nose stopped bleeding.

The big ’plane carried a relay of provisions for the fire fighters already established, whom it had brought for the purpose from the Zuni Mine. As corned beef and hardtack were distributed, the hungry campers thought they had never tasted anything so good in their lives. Not even the Thanksgiving turkeys of later years were ever spiced with such appetites.

This fire,—or rather, these three fires, so mysteriously concomitant, the Ranger explained when the boys returned, had broken so far from any ranch or work camp that they were hard pressed for men to fight it.

“You fellows will have a mighty important part to play for the next few days,” he assured them, “or I miss my guess.”

“Hurray!” shouted Ace. “Three cheers for the U. S. Airplane Patrol!” For he knew something of the work started at the close of the war. Following regular daily routes, this patrol not only detects fires and follows up campers or others who may have started them, (carelessly or otherwise), but in times of emergency carries the fire leader from one strategic point to another,—where as likely as not there are neither roads for him to go in his machine, nor even horse-back trails,—till he has shown the volunteer firemen how to trench and back-fire.

They needed some one, the Ranger said, to hold the top of the next ridge,—between which and the boys lay that inaccessible canyon it would have taken them days to have scaled afoot. By day they were merely to watch for flying brands. Their chief work would come at night, when the wind would turn and blow down canyon, and they might successfully back-fire.

The fire had started in two places on the opposite bank of the Kawa, and in one place this side of the river, and was eating its way along the slopes with the wind which swept them by day. It certainly looked like the work of incendiaries.

Ace begged permission to wireless for his little Spanish ’plane, in its hangar in Burlingame, that it might be employed in some volunteer capacity, and Radcliffe accepted his offer.

The huge DeHaviland required all of the flat surface afforded by the butte, for its preliminary run. They were off with a roar. As they glided across to the flat-topped ridge on the other side of the canyon, they could see the ravenous flames climbing tall pines and firs, racing from limb to limb, through the forest roof, devouring the steeps, doubtless richly coated with underbrush and downwood. The roar and crackle of it filled their ears sickeningly, as they thought of the naked mountainsides that would be left,—mere skeletons of barkless tree trunks, where they had camped on brown pine needles,—smooth, silent, inches deep, soft under their tired feet, dry as tinder and aromatic with Nature’s finest perfume.