take Mr. Damon and Mr. Terrill, fly with
them for some time in the air, and demonstrate how quiet his new craft
was. Then, by contrast, a machine without the muffler and the new motor
with its improved propellers would be flown, making as much noise as
the usual craft did.

"I only wish," said Tom, as the time arrived for the official
government test, "that Mary could be here to see it. She was the one
who really started me on this idea, so to speak, as it was because I
couldn't talk to her that I decided to get up a silent motor."

But Mary Nestor was too grief-stricken over her missing father to come
to the test, which was to take place late one afternoon, starting from
the aerodrome of the Swift plant.

"First," said Tom, to Mr. Terrill, "I'll show you how the machine works
on the ground. I'll run the motor while the plane is held down by means
of ropes and blocks. Then we'll go up in it."

"That suits me," said the agent. "If it does all you say it will do,
and as much as I believe it will do, Uncle Sam will be your debtor, Mr.
Swift."

"Well, we'll see," said Tom with a smile.

Preparations were made with the greatest care, and Tom went over every
detail of the machine twice to make certain that, in spite of the
precautions, no spy had done any hidden damage, that might be
manifested at an inopportune moment. But everything seemed all right,
and, finally, the motor was started, while Mr. Terrill, and some of his
colleagues from the Army Aviation department looked on.

"Contact!" cried Tom, as Jackson indicated that the compression had
been made.

The mechanic nodded, gave the big propeller blades a quarter turn and
jumped back. In an instant the motor was operating, and the craft would
have leaped forward and cleaved the air but for the holding ropes and
blocks. Tom speeded the machinery up to almost the last notch, but
those in the aerodrome hardly heard a sound. It was as though some
great, silent dynamo were working.

"Fine!"

"Wonderful!"

"Wouldn't have believed it possible!"

These were some of the comments of the government inspectors.

"And now for the final test--that in the air," said Mr. Terrill.

Previous to this he and his colleagues had made a minute examination of
the machinery, and had been shown the interior construction of the
silencer by means of one built so that a sectional view could be had.
Tom's principles were pronounced fundamental and simple.

"So simple, in fact, that