here," replied Mr. Vardon, quietly. "I did not expect to see
you here, though."

"The surprise is mutual," mocked the other. "I read about your
failure. I suppose now, you will quit fooling with that gyroscope of
yours, and give my method a trial."

"I never will. I am convinced that I am right, and that you are wrong."

"You're foolish," was the retort.

Jack Butt stepped forward and whispered in the ear of his employer, so
that at least Dick heard what he said.

"I believe HE did it!" were the tense words of the machinist.

CHAPTER VI

DICK'S FIRST FLIGHT

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.

"You must not say such things!" cried the aviator. "You have no proof!"

"I have all the proof I want as far as he is concerned," declared Jack.
"Maybe he didn't intend to kill us, or hurt us, but he sure did want to
wreck the machine when he tampered with the gyroscope."

"What is the gyroscope?" asked Dick.

"It is an invention of mine, and one over which Lieutenant Larson and I
had some argument," said Mr. Vardon.

"You probably know," the aviator went on, while Dick, Paul, and Innis,
with several other cadets, listened interestedly, "you probably know
that one of the great problems of aviat