The reason for the runaway dawned on Bryce instantly.  The road, being privately owned, was, like most logging-roads, neglected as to roadbed and rolling-stock; also it was undermanned, and the brake-man, who also acted as switchman, had failed to set the hand-brakes on the leading truck after the engineer had locked the air-brakes.  As a result, during the five or six minutes required to “spot in” the caboose, and an extra minute or two lost while the brakeman struggled with the recalcitrant lock on the switch, the air had leaked away through the worn valves and rubber tubing, and the brakes had been released—­so that the train, without warning, had quietly and almost noiselessly slid out of the log-landing and started on its mad career.  Before the engineer could beat it to the other switch with the locomotive, run out on the main track, let the runaway gradually catch up with him and hold it—­no matter how or what happened to him or his engine—­the first logging-truck had cleared the switch and blocked pursuit.  There was nothing to do now save watch the wild runaway and pray, for of all the mad runaways in a mad world, a loaded logging-train is by far the worst.

For an instant after realizing his predicament, Bryce Cardigan was tempted to jump and take his chance on a few broken bones, before the train could reach a greater speed than twenty miles an hour.  His impulse was to run forward and set the handbrake on the leading truck, but a glance showed him that even with the train standing still he could not hope to leap from truck to truck and land on the round, freshly peeled surface of the logs without slipping for he had no calks in his boots.  And to slip now meant swift and horrible death.

“Too late!” he muttered.  “Even if I could get to the head of the train, I couldn’t stop her with the hand-brake; should I succeed in locking the wheels, the brute would be doing fifty miles an hour by that time—­the front truck would slide and skid, leave the tracks and pile up with me at the bottom of a mess of wrecked rolling-stock and redwood logs.”

Then he remembered.  In the wildly rolling caboose Shirley Sumner rode with her uncle, while less than two miles ahead, the track swung in a sharp curve high up along the hillside above Mad River.  Bryce knew the leading truck would never take that curve at high speed, even if the ancient rolling-stock should hold together until the curve was reached, but would shoot off at a tangent into the canyon, carrying trucks, logs, and caboose with it, rolling over and over down the hillside to the river.

“The caboose must be cut out of this runaway,” Bryce soliloquized, “and it must be cut out in a devil of a hurry.  Here goes nothing in particular, and may God be good to my dear old man.”