ad the utmost confidence in his own judgment, and believed he would
bring up at the identical place which was their goal.

Tom now volplaned again, wishing to draw nearer to the earth. It was
while thus dropping, with engine muffled, that his ears caught a sound
calculated to give him an uneasy feeling.

This was undoubtedly the whirr of a propeller beating the air in furious
fashion. It also came from behind. Jack, too, had caught the sound, and
was thrilled with sudden apprehension of impending trouble.

They were undoubtedly being pursued, and by a much faster plane than
their own. This would mean that presently they would be overtaken and
fired upon. It was not in the nature of Tom Raymond to allow such a
thing to occur and be kept from doing his share of the fighting.

When Tom swung around to face the rear, and actually started to run
toward the oncoming foe, Jack knew what was expected of him. He must man
the gun, and prove how well he had learned his lesson when at school at
Pau and at Casso.

No longer could they expect to be guided by sounds. Their own motor
thundered so loudly that every other sound was deadened. They must
depend on eyesight alone to tell them when they were nearing the
oncoming Fokker craft. Perhaps the first indication they would have of
its presence would be the flash of its quick-firing gun, spattering
bullets around them like hail.

So Jack strained his vision to the limit. He was eager to discover the
enemy before they themselves were seen. Much might depend on who fired
first, in a duel of this kind.

Suddenly the gun began to bark after its own peculiar way. Jack believed
he had glimpsed something moving, and was sending forth a storm of lead
in the hope of a lucky hit that would crumple the other machine up and
put an end to that peril.

Tom held the course. He knew that every second was carrying the rival
airplanes nearer together--knew that possibly they were so headed that
if they continued to rush forward they might smash in a frightful
collision that would send both down thousands of feet to the earth.

It was a time for careful calculations and prompt action. Tom gripped
the controls and was ready either to swerve or to dip as occasion
demanded. Meanwhile, Jack was doing his best to riddle the advancing
Boche machine and its pilot.

There was no longer any difficulty in seeing just where the Fokker was,
for a constant flashing as her gun rattled betrayed its position