“You’ve heard of wireless telegraph instruments?”
“Yes.”
“And you know they send messages with them without using wires, don’t you?”
“Yes.”
“Then, too, you’ve heard or read that there are currents of electricity running around the globe in all directions, haven’t you?”
“I—I think I have; yes.”
“Well, the selector picks up or selects any current the operator desires, and enables him to travel over it in his balloon, using it as a propelling power.”
“Well—well!” Bob exploded, in frank admiration. “Just like a trolley car!”
“Yes, except no wire is needed.”
“I don’t see how you tell which way it’ll go, though.”