described.

"Well, I'm ready when you are, Tom," said Mr. Damon.

"We'll go as soon as it's dark," was the reply. "But first I'll
give you a demonstration. Start the motor, Jackson!" Tom called
to his chief helper.

Mr. Damon had ridden in aeroplanes before, and had stood near
when Tom started them; so he was prepared for a great rush of air
as the propellers whirled about, and for deafening explosions
from the engine.

The big blades, of new construction, were turned until the gas
in the cylinders was sufficiently compressed. Then Jackson
stepped back out of danger while Tom threw over the switch.

"Contact!" cried the young inventor.

Jackson gave the blades a quarter pull, and, a moment later, as
he leaped back out of the way, they began to revolve with the
swiftness of light. There was the familiar rush of air as the
wooden wings cut through the atmosphere, but there was scarcely
any noise. Mr. Damon could hardly believe his ears.

"I'm not running her at full speed," said Tom. "If I did she'd
tear loose from the holding blocks. But you can see what little
racket she makes."

"Bless my fountain pen!" cried Mr. Damon. "You are right, Tom