straining and pulling it was finally hauled into the road and
they were ready to resume the trip.

Roy rewarded their helper with a substantial bill, and they were all
warm in their thanks.

"'Twasn't nuthin'," declared the man, "an' now I guess I'll go to ther
house and have my hired man fill in this road. Things is come to a fine
pass when such things kin happen."

As the rescued party sped on toward the aviation field they fully agreed
with the rustic's opinion. Had it not been for sheer luck they would
have suffered extremely serious consequences as the result of a rascal's
device. But as it was Kelly's plot against them appeared to have failed.

CHAPTER XX.

AN ATTACK IN THE AIR.

"B-o-o-m!"

The sound of a gun crashed out as the auto sped through the gates of the
aviation field and rapidly skimmed across to where the aeroplanes had
been parked.

"Just in time!" cried Peggy; "that's the five-minute warning gun."

By this time the grandstand was well filled and a band was playing
lively airs. At the starting line three of the Kelly aeroplanes were
gathered ready for the signal for the start of the altitude flight. The
instant the car came to a standstill Jimsy was out and in a jiffy had
the new spark plug adjusted. There was no time to test it, but he felt
pretty confident that it would work all right.

"All ready!" shouted the official in charge of the starting
arrangements.

"Ready!" rejoined Jimsy heartily, as he adjusted his leather helmet and
Jake and Roy started the engine.

Kelly, whose back had been turned while he talked to some of his troup,
faced round at the sound of the boy's voice.

"What, you here!" he choked out, his face purple.

"Yes; do you know any reason why I shouldn't be?" asked Jimsy, with
meaning emphasis.

Under the lad's direct gaze Kelly's eyes fell. He couldn't face the lad,
but turned away.

"There, if that isn't proof of his guilt I'd like to know what is,"
declared Jimsy to Roy.

"But the rascal covered up his tracks so cleverly that we can't prove
anything on him," muttered Roy disgustedly.

At the same instant the starting bomb boomed out. The crowd yelled, and
the drummer of the band pounded his instrument furiously. Above the
uproar sounded the sharp, crackerlike report of the motors. As more
power was applied they roared like batteries of Gatling guns.

Into the air shot one of them, a black biplane. It was followed by the
others, two monoplanes