nearly mechanically perfect as it was possible to be, Tom Swift
finished his trip around it and stood near the big propeller,
waiting for Mary Nestor to reappear. Presently she did so, and
Tom gaily waved his hand to her.

"You're a picture!" he cried, as he saw how particularly
"fetching" she looked in the aviator's costume which was like his
own. Because of the danger of entanglement, Miss Nestor had
doffed her skirts, and wore the costume of all aviators--men and
women.

"I wish I had my camera!" cried Tom. "You look--stunning!"

"I hope that isn't any comment on how I'm going to feel if we
have to make a--forced landing, I believe you call it," she
retorted.

"Oh, I'll take care of that!" exclaimed Tom. "Now up you go,
and we'll start," and he helped her to climb into the padded seat
of the cockpit, behind where he was to sit.

"Oh, Tom! Don't be in such a hurry !" expostulated Mary. "Let
me get my breath!"

"No!" laughed the young inventor. "If I did you might back out.
Get in, fasten the strap around you and sit still. That's all you
have to do. Don't be afraid, I'll be very careful. And don't try
to yell at me to go slower or lower once we're up in the air.

"Why not?" Mary wanted to know, as she settled herself in her
seat.

"Because I can't very well bear you, or talk to you. The motor
makes so much noise, you know. We can do a little talking through
this speaking tube," and he indicated one, "but it isn't very
satisfactory. So if you have anything to say--"

"In the language of the poets," interrupted Mary, "if I have
words to spill, prepare to spill them now. Well, I haven't! Now
I'm here, go ahead! I shall probably be too frightened to talk,
anyhow."

"Oh, no you won't--after the first little sensation," Tom
assured her. "You'll be crazy about it.  Come on, Jackson!" he
called to the mechanician. "Start the ball rolling!"

Tom was in his place, his goggles and cap well down over his
face, and he was adjusting the switch as the mechanic prepared to
spin the propellers.

Suddenly a man came running from the Swift house, waving his
arms not unlike the blades of an aircraft propeller, he also
shouted, but Tom, whose ears were covered with his fur cap, could
not hear. However, Jackson did, and stopped whirling the blades,
turning about to see what was wanted.

"Why, it's Mr. Damon!" exclaimed Tom, as he caught sight of the
excited man. "Hello, what's the matter?" the youth asked, pulling
aside one flap of his head-covering so he might hear the answer.

"Tom! Wait a minute! Bless my mouse trap!" exclaimed Mr. Damon,
"I want to speak to you!" He was panting from his run across the
field. "I just got to your house--saw your father--he said you
were going up with Miss Nestor, but--bless my dog biscuit--"

"Can't stop now, Mr. Damon!" answered Tom, with a laugh. "I
have only just succeeded, by hard work, in getting Mary to a
point where she has consented to take a sky ride. If I stop now
she'll back out and I'll never get her in again. See you when I
come back," and Tom pulled the covering over his ear once more.

"But, Tom, bless my shoe laces! This is important!"

"So's this!" answered Tom, with a grin. He saw, by the motion
of Mr. Damon's lips, what the latter had said.

Around swung the propeller blades. The gasoline vapor in the
cylinders was being compressed.

"Contact!" called Tom sharply, as he pressed the switch to give
the igniting spark at the proper moment. The mechanic had stepped
back out of the way, in case there should be a premature starting
of the powerful engine, in which event the blades would have cut
him to pieces.

"Wait, Tom! Wait! This is very important! Bless my collar
button, Tom Swift, but this is--"

Bang! Bang! Bang!

With a series of explosions, like those of a machine gun, the
motor started, and further talk was out of the question. Tom
turned on more gas. The propellers became almost invisible blades
of light and shadow, and the aeroplane began moving over the
grassy field. The mechanic had sprung out of the way, pulling Mr.
Damon with him.

"Come back! Come back! Wait a minute, Tom Swift! Bless my pansy
blossoms, I want to tell you something!" cried the little man.

But Tom Swift was away and out of hearing. He had started on
his sky ride with Mary Nestor.

CHAPTER II
A NEW IDEA

Any one who has taken a flight in an aeroplane or gone up in a
balloon, will know exactly how Mary Nestor felt on this, her
first sky ride of any distance. For a moment, as she looked over
the side of the machine, she had a distinct impression, not that
she was going up, but that some one had pulled the earth down
from beneath her and, at the same time, given her a shove off
into space. Such is the first sensation of going aloft. Then the
rush of air all about her, the slightly swaying motion of the
craft, and the vibration caused by the motor took her attention.
But the sensation of the earth dropping away from beneath her
remained with Mary for some time.

This sensation is much greater in a balloon than in an
aeroplane, for a balloon, unless there is a strong wind blowing,
goes straight up, while an aeroplane ascends on a long slant, and
always into the teeth of the wind, to take advantage of its
lifting power on the underside of the planes. The reason for this
sensation--that of the earth's dropping down, instead of one's
feeling, what really happens, that one is ascending--is because
there are no objects by which comparison can be made. If one
starts off on the earth's surface at slow, or at great speed, one
passes stationary objects--houses, posts, trees, and the like--
and judges the speed by the rapidity with which these are left
behind.

Going up is unlike this. There is nothing to pass. One simply
cleaves the air, and only as it rushes past can one be sure of
movement. And as the air is void of color and form, there is no
sensation of passing anything.

So Mary Nestor, as she shot into the air with Tom Swift, had a
sensation as though the earth were dropping from beneath her. For
a moment she felt as though she were in some vast void--floating
in space--and she had a great fear. Then she calmed herself. She
looked at Tom sitting in front of her. Of course, all she could
see was his back, but it looked to be a very sturdy back, indeed,
and he sat there in the aircraft as calmly as though in a chair
on the ground. Then Mary took courage, and ceased to grasp the
sides of the cockpit with a grip that stiffened all her muscles.
She was beginning to "find herself."

On and on, and up and up, went Mary and Tom, in this the girl's
first big sky ride. The earth below seemed farther and farther
away. The wide, green fields became little emerald squares, and
the houses like those in a toy Noah's ark.

Down below, Mr. Wakefield Damon, who had hurried over from his
home in Waterfield to see Tom Swift, gazed aloft at the fast
disappearing aeroplane and its passengers.

"Bless my coal bin!" cried the eccentric man, "but Tom is in a
hurry this morning. Too bad he couldn't have stopped and spoken
to me. It might have been greatly to his advantage. But I suppose
I shall have to wait."

"You want to see Master?" asked a voice behind Mr. Damon, and,
turning, he beheld a veritable giant.

"Yes, Koku, I did," Mr. Damon answered, and he did not appear
at all surprised at the sight of the towering form beside him. "I
wanted to see Tom most particularly. But I shall have to wait.
I'll go in and talk to Mr. Swift."

"Yaas, an' I go talk to Radicate," said the giant. "Him diggin'
up ground where Master told me to make garden. Radicate not
strong enough for dat!"

"Huh! there's trouble as soon as those two get to disputing,"
mused Mr. Damon, as he went toward the house.

Meanwhile, Mary was beginning to enjoy herself. The sensation
of moving rapidly through the air in a machine as skillfully
guided as was the one piloted by Tom Swift was delightful. Up and
up they went, and then suddenly Mary felt a lurch, and the plane,
which was now about a thousand feet high, seemed to slip to one
side.

Mary screamed, and began reaching for the buckle of the safety
belt that fastened her to her seat. She saw that something
unusual had occurred, for Tom was working frantically at the
mechanism in front of him.

But, in spite of this, he seemed aware that Mary was in danger,
not so much, perhaps, from what might happen to the machine, as
what she might do in her terror.

"Oh! Oh!" cried the girl, and Tom heard her above the terrific
noise of the motor, for she was speaking with her lips close to
the tube that served as a sort of inter-communicating telephone
for the craft. "Oh, we are falling! I'm going to jump!"

"Sit still! Sit still for your life!" cried Tom Swift. "I'll
save you all right! Only sit still! Don't jump!"