Around the World in Ten Days Part 7

"Farther than that. With this particular vacuum tube, which will amplify sounds three or four times over any other I have tried, we expect to talk with ground stations or other aircraft at a distance of three thousand miles. Notice what a simple thing it is, dad," and Bob indicated a little gla.s.s bulb which looked a lot like an ordinary incandescent light, but which had a peculiar arrangement of wires and substances inside.

"Is the transmitter or receiver made just like the ordinary kind?"

asked Mr. Giddings.

"Practically the same, dad. The wireless transmitter, like that of the wire telephone, contains a sensitive diaphragm which your voice strikes and sets to vibrating. These vibrations compress and release a capsule of carbon granules which agitate and set in motion an electrical current in two magnets connecting with them. The magnets convey the sound-waves in the form of electrical waves, along wires out to the tip of each wing, where the wires hang down a little way. When a message comes in it is caught by a webbing of antennae wires in our wings."

"Then I suppose these sound-waves, in other words the words one speaks, run out of the end of these wires into the atmosphere?"

"Exactly, sir," agreed Bob. "That is, the electrical waves are projected into the air and disturb this air in a way to make it pulsate in the same manner as your voice makes the diaphragm pulsate. These waves are then carried through the atmosphere in every direction, and sooner or later reach the antennae wires of some station equipped to receive them. Down these wires they dash, are registered and magnified in the wonderfully delicate vacuum tube, and from it are carried up into the receivers at your ears."

"I should think they would be electrical impulses when they reach the receivers," argued Mr. Giddings. "How can a person hear _words_ from electrical discharges?"

Bob smiled. "Easy enough, dad," he went on. "You see, this vacuum tube does the business. The electrical current agitates this in unison, and the impulses are immediately converted into words again,--and there you are!"

"I acknowledge my understanding now," admitted Mr. Giddings, with a hearty laugh; "but there's just one thing yet I want light on: Where do you get your electrical current? It takes a dynamo to make electricity, else storage batteries. I don't see either."

"Come outside here a moment, dad."

Bob smiled as he led the little party out of the Sky-Bird's cabin.

When they once more stood on the hangar floor, he pointed to a peculiar T-shaped object just beneath the nose of the airplane. This had escaped the gentleman's observation until now.

"It looks like a small propeller with a torpedo sticking out from the middle of it," laughed Mr. Giddings.

"So it does, dad," agreed Bob. "Well, that's our wireless dynamo. You will notice that the propeller faces ahead, like the big fellow here.

When the airplane is flying, the rush of wind spins the fan at a terrific rate, its axle operates a little dynamo in this torpedo-like case and manufactures electric current. The current then pa.s.ses into this small apparatus here with a bulb attached, which regulates the voltage and sends it up to the instruments in a uniform flow, no matter at what speed the airplane may be going."

"That's a cheap way of getting current," declared the newspaper man, "and a mighty good one, too." He now changed the subject by asking: "How much do you suppose this machine weighs?"

"I have been in smaller ones which weighed, unloaded, as much as three thousand pounds," admitted John Ross, with a peculiar smile. "Put your hands under the Sky-Bird's nose here and see if you can lift her, Mr.

Giddings."

"Don't joke that way, John," expostulated Mr. Giddings. "Why, her engines are right above this portion of her, and I couldn't lift one of them alone."

"Just try it anyhow, dad," persisted Bob, who also wore that queer smile.

More to accommodate them than because he expected to accomplish anything, the publisher half-heartedly braced himself in a crouching position and pushed upward on the airplane's front. To his amazement the whole forward part of the machine rose upward a foot in the air, as if it were made of paper.

"My word!" exclaimed Mr. Giddings, letting the craft back upon its wheels. "Who would have thought such a thing? I had faith in this principle of the hollow wings and helium-gas, boys, but I never thought it could reduce the normal weight of the plane to such a vast extent, It is truly a wonderful idea."

"You might not believe it, but the Sky-Bird weighs less than two hundred pounds as she stands," said Paul. "Just before you came today, Mr. Giddings, Bob and I, one at each end, easily lifted her clear off the floor."

"It's what we aimed for, and we've got it," added John with satisfaction, while Tom Meeks nodded his head and e.j.a.c.u.l.a.t.ed, "I'd say so! I'd say so!" his whole broad face abeam. "This feather lightness means great lift, great speed, and great cruising range."

"I should think so surely," was the decided response of the newspaper man. "I notice you have installed that 'automatic pilot' too. And what's that up here in front on top of the cabin? A searchlight, as I live!"

"Yes, dad," said Bob; "we thought that would be a good thing in case we do any night traveling on this tour of the world. It ought to have good power, being operated with current from the storage batteries of the wireless wind-dynamo."

After a little more inspection and further questions, Mr. Giddings took his departure, promising to be on hand at the hangar the following morning for the test flight.

CHAPTER IX

THE TEST FLIGHT

John, Paul, and Tom reached the fairgrounds a good full hour ahead of the scheduled start that Sat.u.r.day morning. In fact, Mrs. Ross had given them an earlier breakfast than usual, so that they could give the Sky-Bird II a general going over before it came time for her to make her initial flight.

Of course all three young men were a good deal excited, although they were careful not to let each other know it, for fear of being the target for a little fun from the others. In this effort at reserve, the irrepressible Tom was the least successful of the trio, as might be expected, and when he caught John and Paul slyly winking at each other and glancing in his direction as he nervously tried the same control for the third time, he blurted out: "Oh, you fellows needn't laugh at me! You're just as much on edge as I am, now that we're really going to fly this old bird!"

"Come, Tom, don't try to cover up your nervousness by accusing us of the same thing," protested Paul.

"You're as agitated as a young kid with his first electric toy train, Tom," laughed John. "How much gasoline have we got in the tanks now?"

"The gauge shows ten gallons," said Tom, bending down and looking at the instrument-board in front of the pilot's seat.

"That isn't enough for a decent flight," declared John. "We'll probably be out for at least an hour, and we may use as much as fifteen gallons in that time; that's about half the consumption of ordinary airplanes, you know. We'll shove in twenty gallons more so as to be on the safe side."

"We haven't put in any oil yet," reminded Tom. "We'd better put in about two gallons, I should say. Most planes use about a half-gallon to the hour; if we use half as much, that will give us plenty of grease."

The tanks were in the lower part of the forward fuselage. With the caps removed, a hose was inserted by Paul, and then John forced the gasoline up by a small but powerful handpump until the gauge told that the required additional twenty gallons were in. The same pump would work with the oil also, and soon the viscid fluid had been transferred from the storage can on the hangar floor to its proper tank in the airplane. Thence it would feed itself up into the carbureter of the working engine by a force-pump attached to the engine, as with the gasoline.

The boys had just finished putting in the fuel when Mr. Giddings and Bob drove up in the former's automobile.

"I expect this is a great day for you young men?" said the publisher, with a smile of greeting to all. "I know it is a time I have looked forward to myself for a good many months,--ever since I accepted the challenge of the _Clarion_, in fact. Is the Sky-Bird supplied with gasoline?"

"Yes, sir," said John; "we just got through with that job. We have easily enough fuel aboard now for a couple of hours' flight, and that will be long enough for a first one. New engines are always 'stiff'

and should not be run too long at a stretch."

"Have you run this pair yet?"

"Oh, yes," said Bob. "We have tried them out several times, dad, and in connection with the propeller, too. They work tip-top, either connected or disconnected. I tell you, when they're in connection they certainly do make this big propeller hum!"

"I can't understand how you can operate the propeller in here," said Mr. Giddings, much puzzled. "All the airplanes I have seen have always dashed forward as soon as their propellers began to revolve under impulse of the motor or motors; there was no restraining them. I should think this machine would run through the front end of the hangar here as soon as you--"

"Pardon me, sir," interrupted John, "but we have gone those fellows one better. You forget that in the drawings we showed you there was a set of brakes designed to be worked by a control within reach of the pilot, brakes which will engage these ground wheels a good deal the same as brakes work on automobiles--by a flexible band of steel and grit-filled cotton which is made to compress over a large sort of hub on the inner side of each wheel."

"Very good," said Mr. Giddings; "but I understand that has been tried before, with the result that the airplane at once tipped forward and stuck its nose into the ground, or rather tried to, smashing its propeller to smithereens."

"They will do that every time unless something has been devised to counteract this tendency to pitch over," explained John. "We have devised the thing to prevent it, Mr. Giddings."

"See here, dad," put in Bob at this point. "Stoop down a bit and look under the forward end of the body here."

His father did as requested, and Bob pointed out a circular opening about the size of a saucer, from which protruded the end of an aluminum-encased shaft bearing a small rubber-tired wheel of very st.u.r.dy proportions.

"That is our preventer, dad," smiled his son.

"In a few minutes we'll show you how it works," added John Ross. "I see you are wearing a cap, sir, as I suggested. That is all the special dress you will need, as our enclosed cabin makes helmets and close bundling unnecessary. We fellows will wear our regular working togs."