and it's up to me to see that it doesn't fall down."

"Go to it, Ned! And I'll get busy on my silent motor."

"Getting busy" was Tom Swift's favorite occupation, and when he
was working on a new idea, as was the case now, he was seldom
idle, night or day.

"I have hardly seen you for two weeks," Mary Nestor wrote him
one day. "Aren't you ever coming to see me any more, or take me
for a ride?"

"Yes," Tom wrote back. "I'll be over soon. And perhaps on the
next ride we take I won't have to shout at you through a speaking
tube because the motor makes so much noise."

From this it may be gathered that Tom was on the verge of
success. While not altogether satisfied with his progress, the
young inventor felt that he was on the right track. There were
certain changes that needed to be made in the apparatus he was
building--certain refinements that must be added, and when this
should be done Tom was pretty certain that he would have what
would prove to be a very quiet aeroplane, if not an absolutely
silent one.

The young inventor was engaged one day with some of the last
details of the experiment. The new motor, with the silencer and
the changed cylinders, had been attached to one of Tom's speedy
aeroplanes, and he was making some intricate calculations in
relation to a new cylinder block, to be used when he started to