"The wings and fuselage are both filled," said Paul; "that is what makes the Sky-Bird so light. If you had brought more helium the last time you were here, I could have pumped in twice the quantity, I think, and that would have made her so light she would rise of her own accord, I really believe. As it is, she now weighs less than a half-ounce. I had the scales on her yesterday."
John shared his brother's enthusiasm. "Fine!" he cried, with sparkling eyes. "Why, that's almost a neutral condition, as she is! Buddy, if we can apply this principle to a full-size machine—and I don't know why we can't—we shall have solved the biggest problem facing airplane designers to-day. With a machine weighing only a trifle more than her load of fuel and baggage, she will not only fly a lot faster but go a lot farther, with a given supply of fuel, than the present-day planes. And what is more, she could attain good speed with a single engine of reasonable power, where now many machines are handicapped with the burdensome weight of an extra power-plant. When will she be ready to test out?"
"I had planned to give her a trial in the old fair-grounds Saturday afternoon," said Paul. "I've asked Bob Giddings to go along."
"That's all right; Bob is a fine lad," said John; "but since you have set the trial for Saturday afternoon, and Bob's father is usually at home at that time, why don't you ask him to view the affair also? I'm sure he would enjoy it. He's a great sportsman, you know, like most newspaper men, and considerably interested in aeronautics."
"I had not thought of it; I'll do it," was the prompt response of Paul. "But we must warn him to silence, John. Whatever happens, we don't wish this to get into the Daily Independent."
"I'd say not," rejoined the former Air Mail pilot sententiously. "Mum's the word; we've got something here, Buddy. Unless I'm greatly mistaken we'll be consulting with the Patent Office at Washington much sooner than little mother anticipates." He poked Paul in the ribs as he spoke, and both young men gave vent to a low chuckle of intense satisfaction. It was an even greater pleasure to look forward to surprising their mother than to astonishing the world and winning its plaudits.
As good an airplane mechanic and flyer as John Ross was, his younger brother was little behind him in the matter of skill in handling a modern machine. It had been John's habit to return to Yonkers every two weeks for a week's lay-off, as customary with other pilots in the Air Mail service. On these occasions he had arrived in his plane, and during the term of his stay had often taken Paul up into the air for pleasure flights, as well as his chum Bob Giddings. Both boys were keen students, and it was not long before John could trust them to operate his big Martin with every confidence. Once, indeed, he and Paul had been caught over Long Island Sound in a bad storm, when the latter was in the pilot's seat, but Paul had brought the craft through like a veteran, winning his brother's unstinted praise and undying respect.
CHAPTER III
A SUCCESSFUL MODEL
Mr. Giddings was glad to accept the invitation to the trial flight. He and his son met the Ross boys at the old race-course Saturday afternoon. This immense, level field, with its one-mile oval and great empty sheds, at one time had been the county's boasted fair-grounds, but two years prior to the opening of our story it had been sold to Mr. Giddings, whose residence property stretched down the side of Shadynook Hill and joined it. New fair-grounds had then been established in another and more centrally located section of the district. In the old grounds the boys of the neighborhood now went to fly their kites and model airplanes, to hold impromptu bicycle and foot races, and to play tag and hide-and-go-seek in the cavernous sheds and around the numerous sagging stables.