the Air Scout. Tom Swift's improved, silent motor urged it
onward, and as the young inventor listened to catch the noise of
the machinery, his heart gave a bound of hope. For he could
detect only very slight sounds.

"She's a success!" exulted Tom to himself. "She's a success,
but she isn't perfect yet," he added. "I've got to make the
muffler bigger and put in more baffle-plates. Then I think I can
turn the trick."

He swung the machine out over the open country, and then, when
they were up at a height and sailing along easily, he called back
to Mr. Damon in the seat behind him:

"How do you like it?"

"Great!" exclaimed the eccentric man. "Bless my postage stamp,
but it's great! Why, there's hardly a sound, Tom, and I can hear
you quite easily."

"And I can hear you," added Tom. "I don't believe, down below
there," and he nodded toward the earth, though Mr. Damon could
not see this, as the airship, save for a tiny light over the
instrument board, was in darkness, "they know that we're flying
over their heads."

"I agree with you," was the answer. "Tom, my boy, I believe
you've solved the trick! You have produced a silent aeroplane,
and now it's up to the government to make use of it."