orry, but you are too late there," interrupted Dick.

"What type are you using?" the lieutenant cried, dramatically.

"The Vardon. I might say that Mr. Vardon is also building my airship.
It will contain his gyroscope."

"A gyroscope!" cried the former officer. "You are very foolish! You
will come to grief with that. The only safe form is the mercury tube,
of which I am the inventor."

At that moment Vardon himself, who wished to consult Dick on some
point, came into the room, not knowing a caller was there.

"I am sorry," went on the young millionaire, "but I am going to use Mr.
Vardon's gyroscope."

"Then you may as well give up all hope of winning the prize!" sneered
Larson. "You are a very foolish young man. Vardon is a dreamer, a
visionary inventor who will never amount to anything. His gyroscope is
a joke, and--"

"I am sorry you think so," interrupted the aviator. "But you evidently
considered my gyroscope such a good joke that you tried to spoil it."

"I! What do you mean? You shall answer for that!" cried the former
lieutenant, in an unnecessarily dramatic manner.

"I think you know what I mean," replied Vardon, coolly. "I need not go
into details. Only I warn you that if you are seen tampering about the
Hamilton airship, on which I am working, that you will not get off so
easily as you did in my case!"

"Be careful!" warned Larson. "You are treading on dangerous ground!"

"And so are you," warned the aviator, not allowing himself to get
excited as did Larson. "I know of what I am speaking."

"Then I want to tell you that you are laboring under a
misapprehension," sneered the former officer. "I can see that I am not
welcome here. I'll go."

Dick did not ask him to stay. The young millionaire was anything but a
hypocrite.

"What did he want?" asked Mr. Vardon, when Larson had left.

"To build my airship. He evidently did not know that I had already
engaged you. He got a surprise, I think."

"He is a dangerous man, and an unscrupulous one," said the aviator. "I
do not say that through any malice, but because I firmly believe it. I
would never trust him."

"Nor shall I," added Dick. "I presume though, that he will have some
feeling against me for this."

"Very likely," agreed Mr. Vardon. "You will have to be on your guard."

The young millionaire and the aviator then went into details about some
complicated point in the construction of the Abaris, with which it is
not ne