vice which your friend believes he has invented, but which he may
have read about somewhere and unconsciously copied, comes into
general use, we hope the deaths will become much less frequent. I am
using a stability device right now on this monoplane. It was
installed by the firm that patented it. You can see how it acts
automatically to steady the machine, no matter how we move about.
And I am almost as safe up in a squally wind as on a calm day."

He took Hugh much higher than he had the others, as the barograph that
was within seeing distance from their seat told the boy, who had
learned how to read its figures.

Half an hour later they came back toward the field again, and descended
to lower currents. The picture Hugh gazed upon as he looked down would
never be forgotten. He could see for miles and miles in every
direction; and how different the country looked from anything he had
ever imagined!

All at once Hugh made a discovery.

"I am almost certain I saw two men hide themselves in that patch of
bushes ahead there," he hastily told the pilot; "and it seemed to me
that they must be the pair of spies who have been giving you so much
trouble. They were creeping toward the camp as if they meant to try
and steal in the back way."

The lieutenant laughed as though pleased.

"Good for you, Hugh," he remarked. "Those sharp eyes of yours let
nothing escape. Now we'll just circle around a bit and give those
precious foreigners the scare of their lives. I happen to have a
supply of small experimental bombs along, which are heavy enough to
frighten them into believing one of the new explosives may follow,
after we have the range. Watch out for some fun, my son!"

CHAPTER XI

GOOD-BY TO THE FOREIGN SPIES

When Hugh saw the air pilot reach back and take a small black object
from a box attached to the body of the monoplane close to the gasoline
tank, he knew that those skulkers below were in for a lively time of it.

Undoubtedly they had been creeping toward the rear of the camp with
the hope either of picking up valuable information, or finding a
chance to make way with precious plans connected with this latest war
airship which Uncle Sam was trying out, and which possessed features
far in advance of anything known abroad.

At a certain second, when he judged that he could drop the bomb very
close to where the couple were secreted, the lieutenant hastened to
do this. Almost immediately afterwar