"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 practically wipe out your troubles in sending and receiving?"
"Because there is even less of it in the world than there is of radium," was the startling reply. "At present Z. 2. X. costs far more than radium. It is the most intensely radio-active stuff in the world. It is capable of being wrought into metal if anybody had ever found enough of it, but except for a small deposit in South Africa, which has been devoted to experimental purposes, nobody has any.
"But enough of that now. That is only a dream. I am anxious, though, to test out my present apparatus thoroughly, and to do it I shall need the help of you boys."
"In what way?" asked Jack.
"In giving it a thorough trial to ascertain over how great a space I can transmit wireless speech."
"Are you going to put up another station outside the grounds?" asked Tom.
"No; I don't want to attract attention to my experiments. You boys have a wireless telegraph outfit on your Wondership?"