“No; I don’t want to attract attention to my experiments.  You boys have a wireless telegraph outfit on your Wondership?”

Jack nodded.  He was curious, as was Tom, to know the Professor’s plan.  They did not have long to wait.

“I wish you would get the machine ready to install a radio-telephone outfit in its place.  In that way I can gauge the limits of my invention without attracting undue attention, as everybody in this vicinity has seen you in flight and would imagine that you were merely taking a trip through the air.”

“But can you get out an apparatus light enough for us to take up?” asked Jack.

“I am working on that now,” said Mr. Chadwick.  “I’ll have it ready in a week.”

“We’ll be ready for you,” promised Jack.

CHAPTER VII.

The great test.

A week later to the day on a sunshiny, windless morning, the Wondership was run out of its shed, glistening with new paint and with every bit of bright work burnished till it shone and sparkled like newly-minted silver.  Amidships on the craft, the general construction of which is familiar to readers of foregoing volumes of this series, was a square metal box with small wires leading to long copper wires stretched from end to end of the Wondership’s body.

These long copper wires were to form the aerials by which the messages from Mr. Chadwick’s workshop were to be caught.  The smaller wires underneath were connected with the metal work of the engine.  These wires formed a “ground” similar to the kind employed in aerial wireless telegraphy.

The details of the Wondership having been fully described in the Boy Inventors’ Flying Ship, we shall not enter here into any but a brief and general description of the craft.  The Wondership, then, was a combination of dirigible balloon, automobile and boat.  Her motive power was furnished by engines driven by an explosive volatile gas which was also used when occasion arose to inflate the bag of the balloon feature of her design.  The gas was generated in the lower part of the craft’s semi-cylindrical metal body.

On land two big aerial propellers, geared to the engine, drove the Wondership swiftly along on four solid-tired wheels.  When it was desired to take to the air the balloon bag, which was neatly folded on a framework supported by upright stanchions above the body of the car, was inflated by turning on a valve connecting with the gas tanks in the base of the body.

When the Wondership was intended to navigate the water she was driven by the same aerial propellers that afforded her motive power on land or in the air.  She then became what may be called a hydromobile.  If it chanced to be rough weather, special hermetically sealed panels could be drawn together, completely enclosing the body and making the craft a water-tight “bottle.”  Ventilation was provided in such a case by a hollow telescopic tube which reached twenty-five feet into the air.  It was divided in two.  Fresh air was drawn by a fan down one section, while the stale air in the “cabin” was forced out by a similar device up the other part of the tube.  Stability was afforded by hollow pontoons, which worked on toggle joints, and could be raised or lowered as desired.