"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."