Swift! Why, I can hear you talk almost as easily as if no engine
were going. And I don't have to shout my head off, either."

This was perfectly true. Tom could converse with Mr. Damon in
almost ordinary tones. The exhaust from the motor was nearly
completely muffled.

"Out in the air it will seem even more quiet," said Tom. "I'll
soon give you a chance to verify that statement."

He ran the engine a little longer, the aeroplane quivering with
the vibrations, but remaining almost silent.

"I'm anxious to see what she'll do when in motion," said Tom,
as he shut off the gas and spark.

Soon after supper, when the shades of evening were falling, he
and Mr. Damon took their places in the first of the Air Scouts,
to give it the preliminary test in actual flying.

Would Tom's hopes be justified or would he be disappointed?



CHAPTER XII
THE CRY FOR HELP


"All ready, Mr. Damon?" asked Tom, as he looked to see that all
the levers, wheels, valves, and other controls were in working