ds he caused the monoplane to
make a curve, so that they would be in shape to circle around that
particular spot and repeat the bombardment as long as the supply of
missiles held out.

Twisting his head so that he could watch the result, Hugh's gaze
followed the descending bomb until it struck the ground. Instantly
there was a pretty loud racket and the dirt flew, although this
missile undoubtedly contained but a small portion of the new and
terrible explosive, being intended only for experimental purposes in
the way of gauging distances correctly.

The two spies instantly sprang into view and started to dash madly
away. They undoubtedly labored under the impression that once the
range had been properly found, one of those fearful projectiles would
be dropped down on them. No doubt they had before now examined the
great hole in the earth showing where aviators had dropped one of the
larger bombs, and knew what to expect in case such a missile fell
anywhere near them.

"You've given them a bad scare already, sir!" remarked Hugh, greatly
enjoying the experience, although it made him think of a fable in one
of his earlier books concerning the sport of stoning that was "fun for
the boy but death to the frogs."

"That is only a beginning," declared the lieutenant. "This monoplane
is so well constructed that we can hover over them, no matter what
they do, just as a hawk shadows a rabbit."

Indeed, the entire performance did remind Hugh of occasions when he
had watched a red-tailed hawk chasing a frightened bunny, now slowing
up on quivering pinions, then making numerous pretended lunges in
order to frighten the quarry still more, and finally ending the
pursuit by a well-directed swoop that gave the bird of prey its
fine dinner.

The two men were bewildered as well as alarmed. Another bomb
exploded close behind them, and started them off on a new tack.
Run which way they might, it seemed as though that terrible enemy
in the air kept hovering above them, sending a little black object
shooting earthward every half dozen seconds, to be followed by a
sudden crash, many times magnified in their excited imaginations.

Once the taller man started to fire his automatic revolver upwards,
as though in sheer desperation he hoped to cause the air pilot to
give over the chase. The reports sounded like the detonation of
toy fire-crackers to Hugh; and if the bullets came as far as the
monoplane, he heard nothing that sounded