"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 much like our southern cottonwood, and the wood apparently has no grain. It has a surprising toughness and strength, and is a trifle over half the weight of cork, weighing only 7.8 pounds per cubic foot, while the same sized piece of cork weighs 13.7 pounds."
"Has this wood ever been used in constructing full-sized airplanes?" asked Mr. Giddings.
"I think not; but Paul and I believe it will be the coming wood for them," said John with enthusiasm. "We have used it plain on this machine. On a large airplane it ought to be reinforced with transverse sections of very thin spruce laid latticewise. That would add considerably to its natural strength, and increase the total weight very little."
"H'm, h'm!" said the great newspaper publisher, "this is very interesting, I am sure. Now let us see how this little affair behaves itself in the air."
Paul and his brother led the way out into one corner of the big field, so as to bring what slight breeze might spring up into the head of the airplane, explaining that machines without a pilot would keep a better keel under such conditions. John then carefully attached the bicycle-pump and recharged the air-tank, following which he took out his watch to time the flight. Mr. Giddings and Bob also took out their watches.
Paul set the little Sky-Bird down on the hard earth, in a spot where there was no grass or other obstacle, and with his finger on the air-valve, said: "Practically all rubber-band motors require starting the model airplane off by picking it up and tossing it away from you up into the air; but I think this machine will rise from the ground like a large plane, on account of its great lightness and unusual power. We will now see if I am right."
To tell the truth, this being the first time he had really tried the Sky-Bird in a flight, Paul was nervous as he turned the valve, removed his hands from the graceful little plane, and straightened up.