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."

"I'm not quite ready for that yet," replied the young inventor. "I
have several improvements to make. But, when they are finished, I'll
let Uncle Sam know what I have. Then it's up to him."

"And you must be careful, Tom, that some of your rivals don't hear of
your success and get it away from you," warned Mr. Damon, as Tom guided
the Air Scout along the aerial way--an unlighted and limitless path in
the silent darkness.

"Oh, they'll have to get up pretty early in the morning to do that!"
boasted Tom, and afterward he was to recall those words with a bit of
chagrin.

On and on they sailed, and as Tom increased the speed of the motor, and
noted how silently it ran, he began to have high hopes that he had
builded better than he knew. For even with the motor running at almost
full speed there was not noise enough to hinder talk between himself
and Mr. Damon.

Of course there was some little sound. Even the most perfect electric
motor has a sort of hum which can be detected when one is close to it.
But at a little distance a great dynamo in operation appears to be
silence itself.

"I can go this one better, though," said Tom as he sailed along in the
night. "I see where I've made a few mistakes in the baffle plate of the
silencer. I'll correct that and--"

As he spoke the machine gave a lurch, and the motor, instead of
remaining silent, began to cough and splutter as in the former days.

"Bless my rubber boots, Tom! what's the matter?" cried Mr. Damon.

"Something's gone wrong," Tom answered, barely able to hear and make
himself heard above the sudden noise. "I'll have to shut off the power
and glide down. We can make a landing in this big field," for just then
the moon came out from behind a cloud, and Tom saw, below them, a great
meadow, not far from the home of Mary Nestor. He had often landed in
this same place.

"Something has broken in the muffler, I think, letting out some of the
exhaust," he said to Mr. Damon, for, now that the motor was shut off,
Tom could speak in his ordinary tones. "I'll soon have it fixed, or, if
I can't, we can go back in the old style--with the machine making as
much racket as it pleases."

So Tom guided the machine down. It went sile