Around the World in Ten Days | Page 7

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 into the air. For fully three minutes the propeller continued to whirl with undiminished speed, then slowly it began to slow up, and finally stopped.
Both Mr. Giddings and his son wiped their hot brows as they handed the plane over to its makers.
"Whew!" said Bob, "that little mule has got a lot of pull to her."
"That she has," supplemented his father. "What sort of material is her frame made of?"
"Balsa-wood," said John.
"I never heard of that. Is it something new?"
"Yes,--to the arts of civilization, but I presume it has been used by the Indians of Ecuador, where it grows, for scores of years in the making of rafts, for which it is particularly well adapted. The tree looks