.

A sort of metal helmet with two receivers attached to it, one on each
side, lay handy at Jack's hand. In front of him was the transmitter
joined to the metal box which contained the microphone, transformers
and inductance tuning coil. Tuning in the aerial apparatus was
effected by means of a small knob projecting through a slit in the
metal box enclosing the delicate instruments including the detector.
By working this knob the tuning block was moved up and down the coil
till a proper "pitch" was obtained.

Jack experienced an odd thrill as he prepared to send the first spoken
word ever exchanged between an airship in motion and a station on
land. He and Tom had sent plenty of wireless messages while soaring
through the ether, but somehow, the dot and dash system had not half
the fascination and mystery of the possibility of exchanging coherent
speech between land and air.

He placed his lips close to the receiver, and with his hand on the
tuning knob sent forth a loud, clear hail:

"Hullo, High Towers!"

There was no answer for a few seconds while he patiently adjusted the
tuning knob. But then came a faint buzz like the humming of a drowsy
bee. Suddenly, sharp and distinct, as if his father was at his elbow,
came Mr. Chadwick's voice in reply:

"Hullo!"

"This is the Wondership. Three thousand feet in the air," cried Jack.

"Congratulations, my boy. It's a success so far."

"What shall we do now?" asked Jack.

"I want you to fly in the direction of Rayburn, and try to keep in
communication all the way."

"All right, dad," responded Jack, and altered the course of the
Wondership.

Rayburn was a small village some twenty-five miles to the north of
Nestorville. Jack kept the receivers on his ears as he flew along.
From time to time he exchanged conversation with his father. So far
everything appeared to be working as if there were no limit to the
distance over which the voices from the air and land could converse.

But suddenly there came a startling interruption to the experiments.

Jack felt a sharp "Bang" at his ears as if a small cannon had been
fired close at hand.

CHAPTER VIII.

TALKING THROUGH SPACE.

As the distance increased between air and land stations, the currents
became stronger, and frequent tuning was necessary. But Jack was able
to keep up a constant conversation with his father, telling him all
the details of the country as they flew along. The sudden explosion,
howeve