Near noon of the following day a man came upstream to report a jam beyond the powers of the outlying rivermen. Roaring Dick, after a short absence for examination, returned to call off the rear. All repaired to the scene of obstruction.

Bob noticed the slack water a mile or so above the jam. The river was quite covered with logs pressed tight against each other by the force of the interrupted current, but still floating. A little farther along the increasing pressure had lifted some of them clear of the water. They upended slightly, or lay in hollows between the others. Still farther downstream the salient features of a jam multiplied. More timbers stuck out at angles from the surface; some were even lifted bodily. An abattis formed, menacing and formidable, against which even the mighty dynamics of the river pushed in vain. Then at last the little group arrived at the "breast" itself--a sullen and fearful tangle like a gigantic pile of jackstraws. Beneath it the diminished river boiled out angrily. By the very fact of its lessened volume Bob could guess at the pressure above. Immediately the rivermen ran out on this tangle, and, after a moment devoted to inspection, set to work with their peavies. Bob started to follow, but Welton held him back.

"It's dangerous for a man not used to it. The jam may go out at any time, and when she goes, she goes sky-hooting."

But in the event his precaution turned out useless. All day the men rolled logs into the current below the dam. The _click!_ clank! clank! of their peavies sounded like the valves of some great engine, so regular was the periodicity of their metallic recurrence. They made quite a hole in the breast; and several times the jam shrugged, creaked and settled, but always to a more solid look. Billy, the teamster, brought down his horses. By means of long blocks and tackle they set to yanking out logs from certain places specified by Roaring Dick. Still the jam proved obstinate.

"I hate to do it," said Roaring Dick to Welton; "but it's a case of powder."

"Tie into it," agreed Welton. "What's a few smashed logs compared to hanging the drive?"

Dick nodded. He picked up a little canvas lunch bag from a stump where, earlier in the day, he had hung it, and from it extracted several sticks of giant powder, a length of fuse and several caps. These he prepared. Then he and Welton walked out over the jam, examining it carefully, and consulting together at length. Finally Roaring Dick placed his charge far down in the interstices, lit the fuse and walked calmly ashore. The men leisurely placed themselves out of harm's way. Welton joined Bob behind a big burned stub.

"Will that start her sure?" asked Bob.

"Depends on whether we guessed right on the key log," said Welton.

A great roar shook the atmosphere. Straight up into the air spurted the cloud of the explosion. Through the white smoke Bob could see the flame and four or five big logs, like upleaping, dim giants. Then he dodged back from the rain of bark and splinters.

The immediate effect on the jam was not apparent. It fell forward into the opening made by the explosion, and a light but perceptible movement ran through the waiting timbers up the river. But the men, running out immediately, soon made it evident that the desired result had been attained. Their efforts now seemed to gain definite effects. An uneasiness ran through the hithert............