"Why, by condensation or compression, I suppose," was the
rather slow answer. "You know they have condensed, or compressed,
air until it is liquid. I've done it myself, as an experiment."

"That's it, Tom! That's it!" cried Mr. Damon in delight.
"Compressed air will do the trick! Not compressed to a liquid,
exactly, but almost so. I'm going to revolve the propellers of my
new airship in compressed air, so dense that they will not have
to have a speed of more than seven hundred revolutions a minute.
What's that compared to the three to ten thousand revolutions of
the propellers now used? The propellers of Damon's Whizzer will
be of the pusher type, and will revolve in dense, compressed air,
almost like water, and that will do away with high speed motors,
with all their complications, and make traveling in the clouds as
simple as taking out a little one-cylinder motor boat. How's
that, Tom Swift? How's that for an idea?"

To Mr. Damon's disappointment, Tom was not enthusiastic. The
young inventor gazed at his eccentric friend, and then said
slowly:

"Well, that's all right in theory, but how is it going to work
out in practice?"

"That's what I came to see you about, Tom," was the reply.
"Bless my tall hat! but that's just why I hurried over here. I
wanted to tell you when I saw you going off on a trip with Miss
Nestor. That's my big idea--Damon's Whizzer --propellers
revolving in compressed air like water. Isn't that great?"