asked Jack.

"Not more than five to eight per cent. of the total energy. So
therefore the waste is enormous. In wireless telegraphy, on the other
hand, the entire energy radiated from a sending station can be picked
up to the limit of the receiver's capacity to detect it."

"Isn't there any way in which this difficulty could be overcome?"
inquired Tom.

"Yes, there is," said Mr. Chadwick, after a moment's thought, "and I
believe that I am the only man in the world employed with radio
telephonic problems who knows of it."

"Why can't you use it, then?" asked Jack.

"Because there are almost insurmountable difficulties in the way.
There is a substance chemically known Z. 2. X. which, if it could be
applied to purposes of transmission and detection, has such immense
powers of electrical absorption that messages could be sent almost any
distance, and with far greater economy of power than at present."

"How far can you send them now?" asked Jack.

"About five miles. At least I think so. I'm not even sure of that,"
was Mr. Chadwick's reply.

But Jack was impatient to get back to Z. 2. X.

"Why can't you use this Z. 2. X.," he questioned, "if it would