r. Nestor was dead.
That he was alive was Tom Swift's firm opinion, and he was doing all he
could to prove it.

It was not until the day after the visit of Mr. Gale that Tom, having
concluded some intricate calculations about the strength of cylinder
valves, uttered an exclamation.

"I wonder if he could have meant that?" cried the young inventor. "I
wonder if he could have meant that? I must find out at once! Queer I
didn't think of that before!"

He put in a long distance call to New York, asking to speak to Mr.
Gale. But when, eventually, he was connected with the office of the
Universal Flying Machine Company he was told that Mr. Gale and Mr. Ware
had sailed for France that day, going over as government
representatives to investigate aeroplane motors. Gale's visit to Tom
had been just previous to taking the boat, it was said.

"This is tough luck!" mused Tom, his suspicions doubly aroused now. "I
can't let this rest here! I've got to get after it! As soon as I make
this final test, and invite Uncle Sam's experts out to see how my
noiseless motor works, I'll get after Gale and Ware if I have to follow
them to the battlefields of France! I wonder if it was that he was
hinting at all the while! I begin to believe it was!"

Tom Swift had decided on another flight for his new craft before he
would let the government experts see it.

"Silent Sam must do his very best work for Uncle Sam before I turn him
over," said the young inventor.

"And after this flight I'll offer the machine to the government, and
then devote all my time to finding Mr. Nestor," said Tom. "I'd do it
now, but private matters, however deeply they affect us, must be put
aside to help win the war. But this will end my inventive work until
after Mr. Nestor is found--if he's alive."

Preparations for the test flight went on apace, and one afternoon Tom
and Jackson took their places in the big, new aeroplane. He no longer
feared daylight crowds in case of an accident. They made a good start,
and the motor was so quiet that as Tom passed over his own plant the
men working in the yard, who did not know of the flight, did not look
up to see what was going on. They could not hear the engine.

"I think we've got everything just as we want it, Jackson," said Tom,
much pleased.

"I believe you," answered the mechanician. "It couldn't be better. Now
if--"

And at that moment there came a loud explosion, and Silent Sam began
drifting rapidly toward t