"

She glanced up and seemed to shiver just a trifle.

"Don't be thinking of those things, Mary!" laughed Tom Swift. "Trot
along and get ready. The motor never worked better, and we may break a
few speed records this morning. No traffic cops to stop us, either, as
there might be if we were in an auto."

"There you go, Mary!" exclaimed Tom, as if struck with a new thought.
"You've ridden in an auto with me many a time, and you never were a bit
afraid, though we were in more danger than we'll be this morning."

"Danger, Tom, in an auto? How?"

"Why, danger of a wheel collapsing as we were going full speed; or the
steering knuckle breaking and sending us into a tree; danger of running
into a stone wall or a ditch; danger of some one running into us, or of
us running into some one else. There isn't one of these dangers on a
sky ride."

"No," said Mary slowly. "But there's the danger of falling."

"One against twenty. That's the safety margin. And, if we do fall, it
will be like landing in a feather bed! There, don't wait any longer. Go
and get ready."

Mary sighed, and then, seeming to summon her nerve to her aid, she
smiled brightly, waved her hand to Tom, and hastened toward his home,
where Mrs. Baggert the matronly housekeeper, was waiting to help the
girl attire herself in a flying-suit of leather.

Mary Nestor, who had a very warm place in the heart of Tom Swift, had,
as he stated, some time since promised to take a trip in the air with
the young inventor. But she had kept putting it off, for one reason or
another, until Tom began to despair of ever getting her to accompany
him. To-day, however, when she had called to inquire about his father,
who had been slightly ill, Tom had, after the social visit, insisted on
the promise being kept.

He had his mechanic get out one of the safest, though a speedy, double
machine, and, with Mary to watch, Tom had taken a trial flight, just to
show her how easy it was. It was not the first time she had seen him
take to the air, but now she watched with different emotions, for she
was vitally interested.

Tom had sailed down from aloft, making a landing in the aviation field
he had constructed near his home, and then he had insisted that Mary
should keep her promise to take a sky ride with him.

"Don't be too long now!" called Tom to the girl, as she hurried toward
the house. "Never mind about your hair, or whether your hat's on
straight. You're going to wear a cap, an