waves."

"What do you mean by that?" asked Bob, with interest. "Is it some sort
of joke?"

"Joke, nothing!" replied Frank Brandon. "As a matter of fact, I fully
believe that electro-magnetic waves can as easily be hurled through a
void as through ether."

The boys were silent for a moment, thinking this over. It sounded
revolutionary, but they had great respect for Frank Brandon's judgment.

"There's the Rogers underground aerial," Bob suggested tentatively, and
Brandon took him up quickly.

"Exactly!" he said. "That leans in the direction of what I say. Why, I
believe the day is coming--and it isn't so very far in the future,
either--when no aerial will be used.

"Why, I believe," he added, becoming more and more enthusiastic as he
continued, "that ten years from now we shall simply attach our receiving
outfits to the ground and shall be able to receive even more
satisfactorily than we do to-day." He laughed and added lightly:

"But who am I to assume the role of prophet? Perhaps, like a good many
prophets, I see too much in the future that never will come true."

"I don't believe it," said Bob. "I shouldn't wonder if all your prophesy
will come true in a few years."

"Well," said Herb, with a grin, "it will be a relief not to get any more
broken shins putting up aerials."

Mr. Brandon laughed.

"I'm with you," he said. "I've been there myself."

"Have you read about that radio-controlled tank?" Joe asked. "The one
that was exhibited in Dayton, I mean?"

"I not only read about it, I saw it," Mr. Brandon answered, and the boys
stared at him in surprise. "I happened to be there on business," he
said; "and you can better believe I was on hand when they rolled that
tank through the traffic."

"What did it look like?" asked Jimmy eagerly.

"The car was about eight feet long and three feet high," responded
Brandon. "It was furnished with a motor and storage batteries, and I
guess its speed was about five or six miles an hour."

"And was it really controlled by radio?" put in Herb, wishing that he
had been on the spot.

"Absolutely," returned Brandon. "An automobile followed along behind it
and controlled it entirely by wireless signals. The apparatus that does
all the work is called the selector, and it's only about the size of a
saucer. It decodes the dots and dashes and obeys the command in an
inconceivably short time--about a quarter of a second."

"It can be controlled by an airplane, too, can't i