picked up, the Indian
was off across the plain to the west at the top of his mottled pony's
speed.

When Wilson returned to Alex and Jack he found them busy constructing a
miniature block-house of ties they had thrown from a neighboring car.
"That's the idea," he said, joining them. "We could hold out in that all
night, easily."

"No; leave that opening, Wilse," Jack interposed as Wilson began closing
a gap at one of the corners. "That's to command the bridge. We're going
to fire through, not over."

The boys had just completed their little fort when from the top of the
gully immediately opposite came a spit of flame, followed by the
plaintive hum of a pistol bullet above them. Promptly they dropped below
the ties, and Alex, who had that side, aimed toward the spot at which he
had seen the flash, and as it spat out again, crashed back with his
Winchester. From several points along the opposite level a ragged fire
followed, and continued intermittently.

Then finally, as the boys had half expected, there came a smattering
volley from amid the cars on the sidings behind them. The body of their
assailants had reached the surface on their side.

Now it was that the three began to experience their first real anxiety.
For despite their show of confidence to one another, each secretly knew
that if a determined rush was made from near at hand, there was scarcely
an even chance of their standing it off.

As a provision against this eventuality Wilson did very little firing
during the almost steady exchange of shots that followed, keeping the
chambers of his two revolvers always full. To the same end, Alex and Jack
used their magazine-rifles as single-shots, holding the magazines, fully
charged, in reserve.

"I think I'm getting one of them now and then," Alex was saying about
half an hour after the disappearance of the Indian. "Or else--" He broke
off to fire again. "Unless their ammunition is giving out over there."

Suddenly Jack snapped open his magazine. "Here they come!" he whispered.
Alex scrambled about beside him. Wilson thrust the pistol-barrels through
the loop-hole.

[Illustration: WITH THE BOYS' PRISONER SECURELY BOUND TO THE SADDLE
OF THE WANDERING HORSE, THE INDIAN WAS OFF
ACROSS THE PLAIN.]

From the dark line of the cars rose a shouted command, there came a
ripping volley of a dozen Colts, and a dim group of figures rushed toward
them.

"Now, steady!" warned Alex. "And shoot low!

"_Fire!_"

"