“Well?” demanded Tom, himself a tiptoe with expectation.

“Nothing doing,” replied Jack, shaking his head.  “I guess the thing isn’t at a practical stage yet.”

“Wait a minute, give it a chance,” urged Tom.  “By the way, how about that tuning device, have you tried that yet?”

“No, good gracious, my head must be turning into solid ivory from the neck up.  I guess that’s just what the trouble is.”

Jack began carefully sliding a small block connected to the instruments up and down the coiled wire which formed the tuning apparatus, and brought the sending and receiving ends into harmony just as if they had been two musical instruments.  When the right electric “chord” was struck he should be able to hear, just as in wireless he would be able to catch the message of an instrument whose wave lengths were attuned to his.

Suddenly Tom saw his chum and cousin give a start and then a shout.  Over the space between the workshop and the small shed a human voice had been borne on electric waves.  Sharp and clear as though he had been listening to a “wire” ’phone, Jack caught and recognized his father’s voice: 

“Hul-lo!”

CHAPTER VI.

The radio telephone.

Back and forth through space they talked for quite a time.  The boys were jubilant.  The despair of many inventors, the wireless or radio telephone appeared to be an accomplished fact.  But they didn’t dream how much yet remained to be done.  At length Mr. Chadwick told them to “hang-up” and come back to the workshop.

The boys were glad to do this for they were extremely anxious to learn something of the forces controlling this aerial method of conversation.  So far, they had not the least understanding, beyond a general idea, of how the thing was done.  Of the details by which Mr. Chadwick had worked out this radical departure in telephony, they knew nothing.

“Well, what did you think of it, boys?” asked Mr. Chadwick when they returned to the workshop.

“Wonderful, beyond anything I could have imagined,” declared Jack.

“How far will it work?” asked Tom.

“That’s just the point,” said Mr. Chadwick.  “That’s where I’m at sea.  I need a metal of greater conductivity than any attainable to get real results.  The carbon that I am using does not throw off enough radio activity to produce a sufficient number of electric impulses to the atmosphere.”

Jack and Tom looked puzzled.

“You don’t understand me I see,” said Mr. Chadwick.

“No, I must say I don’t,” said Jack; “you see——­”

“It’s pretty technical,” broke in Tom.

“Well, then I’ll try to explain to you, in simple language, the general principles of radio telephony,” said Mr. Chadwick.  “In the first place you know, of course, from your wireless studies, that an electric wave sent into the air will travel till it strikes something, such as an aerial.”