res hang down a little way. When a message
comes in it is caught by a webbing of antennae wires in our wings."

"Then I suppose these sound-waves, in other words the words one speaks,
run out of the end of these wires into the atmosphere?"

"Exactly, sir," agreed Bob. "That is, the electrical waves are
projected into the air and disturb this air in a way to make it pulsate
in the same manner as your voice makes the diaphragm pulsate. These
waves are then carried through the atmosphere in every direction, and
sooner or later reach the antennae wires of some station equipped to
receive them. Down these wires they dash, are registered and magnified
in the wonderfully delicate vacuum tube, and from it are carried up
into the receivers at your ears."

"I should think they would be electrical impulses when they reach the
receivers," argued Mr. Giddings. "How can a person hear _words_ from
electrical discharges?"

Bob smiled. "Easy enough, dad," he went on. "You see, this vacuum
tube does the business. The electrical current agitates this in
unison, and the impulses are immediately converted into words
again,--and there you are!"

"I acknowledge my understanding now," admitted Mr. Giddings, with a
hearty laugh; "but there's just one thing yet I want light on: Where do
you get your electrical current? It takes a dynamo to make
electricity, else storage batteries. I don't see either."

"Come outside here a moment, dad."

Bob smiled as he led the little party out of the Sky-Bird's cabin.
When they once more stood on the hangar floor, he pointed to a peculiar
T-shaped object just beneath the nose of the airplane. This had
escaped the gentleman's observation until now.

"It looks like a small propeller with a torpedo sticking out from the
middle of it," laughed Mr. Giddings.

"So it does, dad," agreed Bob. "Well, that's our wireless dynamo. You
will notice that the propeller faces ahead, like the big fellow here.
When the airplane is flying, the rush of wind spins the fan at a
terrific rate, its axle operates a little dynamo in this torpedo-like
case and manufactures electric current. The current then passes into
this small apparatus here with a bulb attached, which regulates the
voltage and sends it up to the instruments in a uniform flow, no matter
at what speed the airplane may be going."

"That's a cheap way of getting current," declared the newspaper man,
"and a mighty good one, too." He now changed