been discovered, a German craft had immediately risen, and was now in
pursuit.

Glancing over his shoulder, Chester was the first to discover that they
were followed. At the same moment that he perceived the pursuing machine
there came a shot from the enemy.

There was no need for Chester to cry out to Hal. The sound of the shot
told the latter of their danger, and he immediately threw the speed
lever over as far as it would go.

The machine bounded forward.

But the pursuer also came on faster than before; and, while it was
apparent that he was not lessening the distance between the two craft,
he nevertheless was still in range, and his rifle continued to crack.
However, neither the machine nor its three occupants were struck.

Chester took a snap shot at the other craft with his revolver, but the
bullet fell short. While the enemy could pepper them at will with his
rifle, a bullet from the lad's revolver could not reach him.

Hal heard the sound of Chester's revolver, and called out:

"Did you hit him?"

"No!" Chester shouted back, "he's too far behind. But he'll get us in a
minute if we don't do something." To himself he added: "If I only had a
rifle!"

"You be ready with your revolver," Hal called to his friend, "and I'll
soon fix that. It's our only chance."

Abruptly he slackened the speed of the machine, and swiftly the enemy
came on. So suddenly had Hal acted that the man at the wheel of the
pursuing machine could not act promptly enough, and was within range of
Chester's revolver before he could slow down.

As the first machine righted after its abrupt halt, Chester took
deliberate aim and fired, even at the moment that a bullet passed close
to his head.

There was a yell from the pursuing machine. A man leaped suddenly to his
feet, shaking the frail craft violently as he did so, waved his arms
once, twice, and toppled into space.

"I got one of 'em," Chester shouted to Hal, and his lips shut grimly.

"Good for you!" Hal shouted back.

Even Marquis realized that it was time to be pleased, and he sent up a
sharp bark of joy. His canine intelligence told him that something that
threatened had been overcome.

But the man at the wheel of the German aeroplane, now that he was alone,
was not minded to give up the chase. The machine darted at the boys'
craft suddenly, and, but for the fact that Hal at that very moment
happened to glance over his shoulder, the sharp-pointed prow of the
German cra