announced the boss of the
construction camp. "He promised to assist us in case we had any
trouble, and turn about is fair play."

"Right you are, Peterson, and any man who wants to go out can do it."
And word was passed around to this effect.

Dave and Roger listened to this talk and what followed with much
interest. In less than five minutes over thirty men from the
construction camp had signified their willingness to go after the
raiders, and these men were joined by Frank Andrews and three other
civil engineers, all well armed and mounted.

"I'd like to join that crowd and go after those Mexicans!" exclaimed
Dave, his eyes sparkling.

"So would I!" returned the senator's son, quickly. "Those fellows
can't be anything but plain bandits and cattle thieves."

"Sure! No regular revolutionists would come over the border and act in
this fashion."

"What do you say, Dave--shall we go?"

"I'm willing."

"No, no! You young fellows had better stay in the camp," announced
Ralph Obray, who overheard the talk. "Just remember that in a certain
sense I am responsible for your safety while you are under me."

"But those others are going," returned Dave, somewhat reproachfully.

"So they are, Porter. But they are all older than you, and most of
them have had experience in this sort of thing. I would rather that
you stayed here. Maybe if those raiders come this way we'll have our
hands full defending the camp."

Dave and Roger realized that for the head of the camp to express his
desire in this instance was equal practically to a command; so they at
once gave up the idea of following Frank Andrews and the others. The
men rode off quickly, and were soon lost to sight in the darkness of
the night.

An hour of intense anxiety passed. During that time those left in the
camp heard an occasional shot in the distance. Then several shots
seemed much closer. There followed some yelling, and, then about five
minutes later, came a dull explosion.

"That's at the bridge!" exclaimed Dave. "They must be trying to blow
it up!"

The dull explosion was followed by a sudden rattle of rifle and pistol
shots and more yelling. Once or twice some men seemed to come quite
near to the construction camp, the hoof strokes of the horses being
distinctly heard.

All who remained in the camp were on the lookout, and each man stood
ready with his weapon to do what he could to defend the place should
the occasion arise. But with the explosion a