They made a dash up the rough track, heading for a shallow cut which ran through the toe of the next mountain spur, and they had barely gained the cutting when another crash bellowed upon the opposite slope and a buckshot shower of sand and pebbles rattled down upon them.

“That’s right, old top; keep it up!” said Dick grittingly, apostrophizing the unseen O. C. hard-rock men. Then: “I wish Mr. Ackerman would let us get back at ’em once in a while. But he makes us run up a red flag when we’re going to shoot.”

“The chief is right, though,” was Larry’s considered reply. “We can’t afford to put ourselves on a level with those highbinders on the other side of the canyon.”

“Huh! that doesn’t sound much as if you were spoiling for a fight, Larry. Where’s your good Donovan nerve gone to?”

“Never you mind about the Donovan nerve; it’s all right. But I’m not chasing around to find a chance to scrap with somebody. I’m out here this summer to learn all I can about the engineering game—and so are you. And fighting a lot of plug-uglies who won’t play the game fair isn’t any part of our job. Just the same—Gee-wop! but that was a close one!”

It was. Another blast, fired from so far around the curve ahead that they couldn’t even see the smoke of it, hurled a stone as big as a water bucket high in air to drop it just in front of them and fairly between the rails of the track over which they were hastening. Its alighting place was not more than a dozen feet distant, and it snapped the cross-tie upon which it fell as easily as if the heavy timber had been a pine lath.

The two boys dropped their burdens and went to roll the stone from the track where it lay a menace to the first material train that should come along. It was so big and weighty that it took their united efforts to edge it over the rail and start it rolling down the embankment.

“Lucky it didn’t hit a rail,” was Larry’s comment, as they went on. “It would have broken the steel as easily as it did the tie.”

“Seems as if there ought to be some law to hold those fellows down!” said Dick wrathfully. “If father would only come up here once and see what they’re doing to us!”

Larry chuckled quietly.