Mr. Vardon gave his helper a quick and warning glance.

"Hush!" he exclaimed, as he looked to see if Lieutenant Larson had
heard what Jack had said. But the army man evidently had not. He
gave the machinist a glance, however, that was not the most pleasant
in the world. It was evident that there was some feeling between
the two. Dick wondered what it was, and what Jack's ominous words
meant.

Having put away the two biplanes, and requested the cadets to look
at them as much as they liked, but not to meddle with the apparatus,
the two lieutenants left the sheds, to report to their respective
captains. Mr. Vardon and his helper remained with Dick and his
chums.

"Very fine machines," said the aviator. "Compared to my poor pile
of junk, very fine machines indeed!"

"But part of yours is good; isn't it?" asked Dick. "You can use
part of it, I should think."

"Very little," was the hopeless reply. "The damage was worse than
I thought. My gyroscope attachment is a total wreck, and it will
cost money to build a new one."

"Yes, and that gyroscope was tampered with before we started on this
last flight!" declared Jack, with conviction. "And I'm sure HE did
it!" he added, pointing an accusing finger at the retreating form
of Lieutenant Larson.