high up, too, I thought."

"But you made sure it was Percy's biplane?" asked Frank, interested
somewhat, for somehow the other rival flier was always doing such bold
stunts that he could not help feeling as though it might pay to keep
track of what he was doing, lest their interests clash unexpectedly, in
midair perhaps.

"I ought to know the way it glides, and the whole general look; and I'd
be willing to take my affidavy that was the Canvas-back, as he calls
his biplane."

"And he was in it, of course, with Sandy too?" Frank went on.

"I could just make out that there were two aboard," said Andy, "but
somehow it seemed to me that Percy had altered his whole way of piloting
his airship, or else he was drunk, and hardly knew what he was doing."

Frank whistled to indicate his surprise and consternation:

"When it gets as rough as that you can take it from me that Percy's
mother will hear something simply awful about him before long. He's
bound to go from bad to worse; and everybody knows what the end of such
an aviator is going to be."

"But what under the sun could he be off at daylight this morning for?"
Andy went on to remark, as though that thing had been bothering him ever
since the moment he lost track of the biplane among the teetering,
cawing crows.

Frank shrugged his shoulders as he replied:

"Did you ever know any reason for half the things Percy does? He just
acts from a sudden impulse. Remember all that happened when he followed
us down there to Columbia in South America, and tried to give us all the
trouble he could make up. And there have been lots of other times too,
we can look back at, all of which prove what I am saying that he is
often like a ship without a rudder. Now, perhaps, he's got the crazy
notion in his head that we might prosecute him either for what he tried
to do up here to our hydroplane, or on account of breaking into our
hangar, and doing a certain amount of damage, if the vandal was Percy
Carberry."

"That sounds a little reasonable, anyhow, Frank. Queer that I never seem
to get hold of these things, and they just float along as easy as
anything to you. But it looks as if we had her all primed up now as
steady as a church. How about it, Frank?"

For answer the other touched several taut wire guys with a peculiar
little movement of finger and thumb, and each one responded with a
musical note that was the sweetest possible sound in the responsive ear
of the young aviators.