Around the World in Ten Days | Page 7

without any of the dirigible's handicap
of clumsiness and excessive wind resistance. He has been studying the
properties of helium in school, also the flight of birds."
"Well, not to get into a tiresome discourse, as Professor Herron would
say, I shall make this description very rudimentary," said Paul, with a
smile. "During a total eclipse of the sun in India in 1868, Lockyer, a
British astronomer, saw in the spectroscope a bright, yellow line of
light around the sun. He called it helium, after the Greek word for sun.
So much for him. Twenty-seven years later an element was found on
earth in natural-gas in Kansas, which gave the same bright, yellow light
viewed through the spectrum. The people, finding it would not burn,
disgustedly let millions of barrels of this valuable element escape into
the air, before a scientist told them that it was of untold value for
balloon and airship purposes. It is thought the gas comes from radium
deposits. It has never been found in any country except the United
States, and only here in Kansas and northern Texas, where it occurs in
sands from 14,000 to 16,000 feet deep. Our government is now
securing about 50,000 cubic feet of helium per day, refusing to sell it to
foreign countries, as it is all needed here, besides which it might be
used against us in case of another war."
While Paul had been telling this, Mr. Giddings had been busy jotting
something down in shorthand in a notebook.
"Pardon me, Paul," he said, looking up with a smile, "but this is so
mighty interesting that, before I knew it, my old-time reportorial
instinct had gotten the best of me, and I found my pencil at work. If
you have no objection I should like to use this in the columns of the
Daily Independent some time when it seems to fit in."
"No objection at all, sir," assured Paul.
Mr. Giddings began twirling the little twelve-inch two-bladed propeller
at the nose of the model airplane. "What do you use for power to turn
this propeller?" he asked, after admiring its perfect proportions for a

moment. "I don't see any rubber-bands, such as Robert here has always
used on his little machines."
John deftly lifted off the thin veneer hood of the airplane, and disclosed
a very small four-cylindered rotary pneumatic engine of bewitching
simplicity and lightness, which a baby could have held out in its pudgy
palm.
"Paul has worked this little motor out of aluminum and brass and steel,
from odds and ends," said John.
"With more or less help on the part of my elder brother," interjected
Paul.
"Well, perhaps with a little," admitted John, "more suggestive than
otherwise."
"What sets it going?" questioned Bob, curiously.
"The fuselage is divided into three sections," said Paul. "The forward
section contains the engine here; the rear section is an airtight chamber
containing helium; and the central section is also an airtight chamber,
but contains ordinary air which has been pumped into it through a valve,
using the bicycle pump John is carrying, until it is under strong
pressure. When I turn this little valve an outlet is opened for the air to
escape by a tube into branches communicating with each of these four
cylinders. This works the tiny pistons, much the same as gas in a
gasoline-motor, and they turn the little crank-shaft to which they are
connected, and the crank-shaft in turn revolves the propeller on its
end."
"Wonderfully simple!" Mr. Giddings exclaimed. "Wonderfully
ingenious, too! Is this your invention, young men?"
"Partly, sir," replied Paul. "I understand, a company in New York is
making a somewhat similar pneumatic motor for model airplanes, but
John and I have made some radical improvements, to our notion.
To-day's test will tell the story."

"Let's see the propeller spin 'er up once for the fun of it," suggested
Bob. "It won't do any harm, will it? Dad and I will hold on to the
airplane."
"Get a good grip then," warned John Ross, "for you will find there's a
terrific pull to the little rascal. Paul and I tried her in that fashion early
this morning down in the basement."
Bob and his father secured firm holds of the little Sky-Bird, one on
each side, where the propeller could not strike them.
"Ready?" asked Paul, with a smile.
"Ready!" came the answer in unison.
Paul touched the little valve in the tank chamber of the fuselage. The
next moment there was a quiver, and then the propeller began fairly to
hum. A strong, steady gust of air began to blow in the faces of the
Giddingses, while they had to hang on grimly in order to keep their
little charge from jumping out of their arms and dashing away