, and crowding her pretty
close to the limit. The wind swept by both sides of the streamlike
cabin with a rushing sound like the distant roar of a huge cataract;
the flexible window glass gave slightly to its pressure, but there was
no sign of it breaking. One minute they were in the midst of a cumulus
cloud; the next, through it. Now they saw the faint outline of the
earth, now sky; now the earth was screened by cloud, but above were the
blue heavens.

"Guess how fast we're making it now?" cried John, one eye on the dial
which connected with the propeller-shaft.

"A hundred miles," ventured Mr. Giddings.

"Hundred and thirty," guessed Paul and Bob.

"Hundred and eighty," stated the more experienced Tom.

"All too low," said John. "We're going just exactly two hundred and
fifty, if this speedometer doesn't lie!"

He now announced that he was going to throw in the idle engine. This
was done successfully, and under the extra power they were soon making
the remarkable speed of three hundred miles an hour! John then slowed
up and disconnected first one motor and then the other, the airplane
continuing to fly with unimpaired smoothness.

As a last test, he dropped to a level of three thousand feet, at which
time they were considerably north of Albany, and throwing the
automatic-pilot into operation calmly removed his hands and feet from
every control except the rudder. In this fashion they ran for fifteen
or twenty miles on a perfectly even keel, the apparatus automatically
working the elevators and ailerons of the craft as various wind
currents tended to disturb its equilibrium. At length, John gave a
little twist to the rudder, and the way the Sky-Bird began to circle,
and to bank of her own accord, was a splendid sight to behold. No
hawk, sailing over a barnyard in quest of an unwary fowl, could have
performed the trick more beautifully.

As the flyers now headed for home they were all much elated at the
success of the first flight of the new airplane. And as it gracefully
swooped down into the fair-grounds a little later, coming to a stop in
a surprisingly short run over the ground owing to her braking feature,
this elation was increased.

CHAPTER X

FINAL PREPARATIONS

After getting out of the airplane, Mr. Giddings was thoughtful for some
minutes. Nor did he speak until the boys had pushed the machine into
the hangar. Then he said, with deep earnestness:

"Young men, a great load has b