nown gentlemen, who seemed to be so
well posted on things aeronautic.

"It was a peach of a dive!" exclaimed Elephant, enthusiastically.

"And since you're wringing wet I don't think you'd better go up with me
again right now," Frank continued. "Hike for home, and get into some
dry duds. I'll knock around for a spell, to try out a few more stunts
I have in mind."

Truth to tell Frank was eager to get his new hydroplane away from those
searching eyes of Mr. Marsh. They gave him a queer feeling, which of
course he was quite unable to understand.

During the preceding summer, when the Bird boys were using the
monoplane they had put together so successfully, it chanced that they
had quite a serious adventure with a couple of thieves who had robbed a
jewelry establishment, and were trying to get out of the country, where
the roads were being closely watched by the police.

On this occasion one of the rascals chanced to be a man named Jules
Garrone, who, over across the water had been something of an aeronaut
and aviator. Conceiving the brilliant scheme that if the monoplane of
the Bird boys could only be stolen he and his companion could easily
elude their hunters, he had given Frank and Andy lots of trouble before
finally falling into the net.

That was one reason why Frank felt rather cool toward strangers who
manifested undue interest in his work. He was of an inventive turn of
mind, and believed he had several new features connected with this
hydroplane that as yet were, so far as he knew, novel to the science of
aviation.

And those keen eyes of Mr. Marsh gave him an uneasy feeling.

"Your biplane seems to be built especially for two?" remarked that
gentleman, as he watched Frank swing the machine around, with the help
of the willing Larry and Elephant.

"Yes, sir," replied the boy, promptly. "Andy and myself always hunt
together. We are called the Siamese Twins, because we won't be
separated. Where one Bird boy is found you can make up your mind the
other isn't very far away. Once on a time they got to calling me
Smoke, and Andy, Fire; but we just wouldn't stand for that."

"But possibly your machine may not fly quite so well with only one to
balance!"

Was that a broad hint that he would be only too glad of an invitation
to occupy the seat left vacant by the departure of Andy? Frank
suspected such a thing; and made a quick reply.

"Oh! we've got all that arranged to a dot, sir," he laughed. "