onders of radio."

"It's a great army all right," laughed Harvey, "and we're always glad to
welcome new recruits. They're coming into the ranks by thousands every
day. Nobody can keep count of them, but they must run into the millions.

"And they're great in quality as well as quantity," he continued, warming
to his favorite subject. "The President of the United States has a radio
receiving set on his desk. There's one in the office of every one of the
ten Cabinet members. The Secretary of the Navy is sending out wireless
messages every day to vessels scattered in all parts of the globe. The
head of the army is keeping in touch by radio with every fort and garrison
and corps area in the United States. On last Arbor Day the Secretary of
Agriculture talked over the radio to more people than ever heard an
address in the history of the world. But there," he said, breaking off
with a laugh, "if I once get going on this line I'll never know when to
stop. So I'll say it all in one sentence--the radio is the most wonderful
invention ever conceived by the mind of man."

"You don't need to prove it to us," laughed Bob. "It's simply a miracle,
and we become more convinced of that every day. I'm mighty glad I was born
in this age of the world."

The boys crowded around Mr. Harvey as he explained to Larry and Tim in as
simple a way as possible the radio apparatus of the station.

"When I press this key," he said, "an electrical spark is sent up into the
antenna, the big wire that you see suspended from the mast over the
station, and is flung out into space."

"Travels pretty fast, doesn't it?" asked Larry, to whom all this was new.

"Rather," laughed Mr. Harvey. "It can go seven and a half times around the
world while you are striking a match."

"What!" exclaimed Larry incredulously. "Why, the circle of the earth is
about twenty-five thousand miles."

"Exactly," smiled Harvey. "And that spark travels at the rate of one
hundred and eighty-six thousand miles a second."

"You're sure you don't mean feet instead of miles?" suggested Tim
dubiously.

"It's miles all right," laughed Harvey. "Electricity travels at the same
rate as the light that comes to us from the sun and stars."

"What becomes of this electrical impulse after it gets started on that
quick trip?" asked Larry. "How does the fellow on the other end get what
you're trying to tell him."

"That fellow or that station has another antenna waiting to receive my
me