made the clink of the stone
hammers ring like a musical chorus beaten out upon steel anvils.
Peaceful, orderly industry struck the key-note, and for the moment there
were no discords. Out on the great ramparts of the dam the masons were
swinging block after block of the face wall into place, and the _burr-r_
and cog-chatter of the huge derrick hoisting gear were incessant. Back
of the masonry the concrete mixers poured their viscous charges into the
forms, and the puddlers walked back and forth on their stagings, tamping
the plastic material into the network of metal bars binding the mass
with the added strength of steel.

Bromley led the way through the stone-yard activities and around the
quarry hill to the path notched in the steep slope of the canyon side.
The second turn brought them to the gap made by the land-slide. It was a
curious breach, abrupt and clean-cut; its shape and depth suggesting the
effect of a mighty hammer blow scoring its groove from the path level to
the river's edge. The material was a compact yellow shale, showing no
signs of disintegration elsewhere.

"What's your notion, Loudon?" said Ballard, when they were standing on
the edge of the newly made gash.

Bromley wagged his head doubtfully.

"I'm not so sure of it now as I thought I was when I came up here this
morning. Do you see that black streak out there on the shale, just about
at the path level? A few hours ago I could have sworn it was a powder
burn; the streak left by a burning fuse. It doesn't look so much like it
now, I'll confess."

"You've 'got 'em' about as bad as Hoskins has," laughed Ballard. "A
dynamite charge that would account for this would advertise itself
pretty loudly in a live camp five hundred yards away. Besides, it would
have had to be drilled before it could be shot, and the drill-holes
would show up--as they don't."

"Yes," was the reply; "I grant you the drill-holes. I guess I have 'got
'em,' as you say. But the bang wouldn't count. Quinlan let off half a
dozen blasts in the quarry at quitting time yesterday, and one jar more
or less just at that time wouldn't have been noticed."

Ballard put his arm across the theorist's shoulders and faced him about
to front the down-canyon industries.

"You mustn't let this mystery-smoke get into your nostrils, Loudon,
boy," he said. "Whatever happens, there must always be two cool heads
and two sets of steady nerves on this job--yours and mine. Now let's go
down the r