The immense doors were open, and I gazed for the first time into the hangar whose s.p.a.cious interior provided storage and manufacturing facilities for a dozen or more planes of Hart Jones' design. A curiously constructed example of his handiwork stood directly before me, and several mechanics were engaged in making it ready for flight. My friend advanced from their midst to meet me, a broad smile on his grease smeared countenance.

"Greetings, Jack," he said, taking my small bag from my hands. "Right on time, I see. And I can't tell you how glad I am that you are coming with us. So is George."

"Well, I didn't expect to," I admitted; "but there is no need of telling you that I had far rather be in your ship than in the big one."

George Boehm, the same jolly chap I had several times met in Hart's company, but fatter than ever, crawled from beneath the shiny metal body of the plane and scrambled to his feet at my side.

"Going in for a bit of adventuring, Mr. Makely?" he asked, wiping his hand with a piece of cotton waste before extending it.

"Yes," I replied, as I squeezed his chubby fingers. "Can't stick in the mud all my life, George. And I wouldn't want to be in better company for my first attempt either."

"Nor we," he returned, a mischievous twinkle in his eyes. "Rather have a greenhorn on the Pioneer than some government agent, who'd be b.u.t.ting in and trying to run everything. Think you'll be scared?"

"Probably," I admitted; "but I guess I can stand it."

"Hear the latest news broadcast?" interrupted Hart Jones.

"No. What was it?" I asked.

"There has been a report from out near Cripple Creek," said Hart solemnly, "that a pillar of fire was observed in the mountains shortly after the time the NY-18 last reported. The time and the location coincide with her probable position and the report was confirmed by no less than three of the natives of that locality. Of course the statements are probably extravagant, but they claim this pillar of fire extended for miles into the heavens and was accompanied by a tremendous roaring sound that ceased abruptly as the light of the flame disappeared, leaving nothing but blackness and awe-inspiring silence behind."

"Lot of bunk!" grunted George, who was vigorously scrubbing the back of his neck.

"Sounds like a fairy tale," I commented.

"Nevertheless, there may be something in it. In fact, there must be.

Three of these mountaineers observed practically the same phenomenon from quite widely separated points, though one of them said there were three pillars of fire and that these looked more like the beams of powerful search-lights. All agreed on the terrific roar. And, after all, these two liners did disappear. There must be something quite out of the ordinary about the way in which they were captured or destroyed, and this occurrence may well be supposed to have a bearing on the matter."

"Possibly they were destroyed by some freak electrical storm," I suggested.

"Where then are the wrecked vessels?" asked Hart. "No, Jack, electrical storms do not destroy huge air liners and then suck them out into s.p.a.ce beyond our vision. These two ships are no longer on the surface of the earth, else they would have been long since located. The magnetic direction finders of the transportation people have covered every inch of the United States, as well as Mexico and Canada."

"Of course they might have been carried halfway around the world by a wind of unprecedented velocity." I commenced a silly argument in favor of the theory that the elements had accounted for the two vessels, but was interrupted by the mounting roar of great engines throbbing overhead.

"Hurry up there, George!" shouted Hart. "It's the SF-22 coming in. We have to be ready for the take-off in five minutes!"

He hastened to take George's place at the washbowl and all was activity within the confines of our hangar. George and I left the office and went out to the landing field, which was now brilliant with the glare of floodlights. The _Pioneer_ had been trundled into the open and stood ready for the flight. Not a hundred feet above the field, the huge silver moth that was the SF-22 swept by in a wide circle that would bring her into the wind. The roar of her engines died as she swung out of the circle of light into the surrounding darkness.

The crowds which had gathered to witness her landing buzzed with excited comment and speculation. Her nose brought slightly up, she dropped to a perfect three-point landing, the brakes screeching as she was brought to a standstill at the hangar of the transportation company.

"Come on now, you fellows," came the voice of Hart Jones from the hangar entrance, "there's no time to lose. The _Pioneer_ takes off immediately after the big fellow."

We hurried to the waiting ship, which seemed like a tiny toy when compared with the giant SF-22. I had observed very little of the construction of the _Pioneer_, but I could now see that she was quite different in design from the ordinary plane. A monoplane she was, but the wing structure was abnormally short and of great thickness, and there were a number of tubes projecting from the leading edge that gave the appearance of a battery of small cannon. The body, like all planes designed for travel in air-level six, was cigar-shaped, and had hermetically sealed ports and entrance manholes. A cl.u.s.ter of the cannon-shaped tubes enclosed the tail just back of the fins and rudder and, behind the wing structure atop the curved upper surface of the body, there was a sphere of gleaming metal that was probably three feet in diameter.

Before I could formulate questions regarding the unusual features of the design, we were within the _Pioneer's_ cabin and Hart Jones was engaged in clamping the entrance manhole cover to its rubber seat. A throbbing roar that penetrated our double hull attracted my attention and, looking through a nearby porthole, I saw that the convoy of army planes had taken off and was circling over the SF-22 in antic.i.p.ation of her start.

Trim, speedy fighting ships these were, with heavy caliber machine-guns in turrets fore and aft and normally manned by crews of twelve each. The under surfaces of their bodies glistened smooth and sleek in the light from the field, for the landing gears had been drawn within and the openings sealed by the close-fitted armor plate that protected these ordinarily vulnerable portions when in flight.

The SF-22 was ready to take off and the crowds were drawing back into the obscurity beyond the huge circle of blinding light. One after another her twelve engines sputtered into life, and ponderously she moved over the field, gathering speed as the staccato barking of the exhausts gradually blended into a smooth though deafening purr. The tail of the great vessel came up, then the wheels, and she was off into the night.

Hart Jones sat at a bewildering array of instruments that covered almost the entire forward part.i.tion of the cabin. He pressed a b.u.t.ton and the starting motor whined for a moment. Then the single engine of the _Pioneer_ coughed and roared. Slowly we taxied in the direction taken by the SF-22, whose lights were now vanishing in the darkness. I saw George open a valve on the wall and Hart stretched the fingers of his left hand to what appeared to be the keyboard of a typewriter set into the instrument board. He pressed several of the keys and pulled back his stick. There was a whistling scream from astern and I was thrown back in my seat with painful force. With that, the motor roared into full speed and we had left the airport far behind.

"What on earth?" I gasped.

"Rocket propulsion," laughed Hart. "I should have warned you. Those tubes you saw outside at the tail and along the leading edge of the wings. Only used three of them, but that was sufficient for the take-off."

"But I thought this rocket business was not feasible on account of the wastage of fuel due to its low efficiency," I objected.

"We should worry about fuel," said Hart.

I looked about me and saw that there was very little s.p.a.ce for the storage of this essential commodity. "Why?" I inquired. "What fuel do you use?"

"Make our own," he replied shortly. He was busy at the moment, maneuvering the _Pioneer_ into a position above and behind the SF-22 and her convoy.

"You make your own fuel enroute?" I asked in astonishment.

"Yes. That sphere you saw on top. It is the collecting end of an electrical system for extracting nitrogen and other elements, from the air. This extraction goes on constantly while we are in the atmosphere and my fuel is an extremely powerful explosive of which nitrates are the base. The supply is replenished continuously, so we have no fear of running short even in the upper levels."

George had crawled through a small opening into some inaccessible region in the stern of the vessel. I pondered over what Hart had just told me, still keeping my eyes glued to the port, through which could be seen the fleet we were following. The altimeter registered thirty-five thousand feet. We were entering air-level six--the stratosphere! Below us the troposphere, divided into five levels, each of seven thousand feet, teemed with the life of the air. The regular lanes were filled with traffic, the lights of the speeding thousands of freight and pleasure craft moving in orderly procession along their prescribed routes.

Up here in the sixth level, which was entirely for high-speed traffic of commercial and government vessels making transcontinental or transoceanic voyages, we were the only adventurers in sight--we and the convoyed liner we were following. The speed indicator showed six hundred miles an hour, and the tiny spot of light that traveled over the chart to indicate our position showed that we were nearing Buffalo.

Glancing through one of the lower ports, I saw the lights of the city shining dimly through a light mist that fringed the sh.o.r.e of Lake Erie and extended northward along the Niagara. Then we were out over the lake, and the luminous hue was slipping rapidly behind. I looked ahead and saw that the distance to the SF-22 and her convoy had somewhat increased. We were a mile behind and some two thousand feet above them.

Evidently Hart was figuring on keeping at a safe distance for observation of anything that might happen.

Our motor was running smoothly and the angle of the propeller blades had been altered to take care of the change in air density from the lower alt.i.tudes. It flashed across my mind that this was an ideal location for an attack, if such was to be made on the SF-22.

Then, far ahead, I saw a beam of light stab through the darkness and strike the tossing surface of the lake. Another and another followed, and I could see that the SF-22 and her convoy were surrounded by these unearthly rays. They converged from high above to outline a brilliant circle where they met on the surface of the waters, and in the midst of the cone formed by the beams, the liner and its seven tiny followers could be seen to falter, and huddle more closely together.

It all happened in the twinkling of an eye--so quickly, in fact, that Hart and I had not the time to exchange remarks over the strange occurrence. For a moment the eight vessels hovered, halted suddenly by this inexplicable force from out the heavens. Then there rose from the apex of the inverted cone of light a blinding column of blue-white radiance that poured skyward an instant and was gone. To our ears came a terrific roaring that could be likened to nothing we had heard on earth.

The _Pioneer_ was tossed and buffeted as by a cyclone, and George came tumbling from the opening he had entered, his round face grown solemn.

Then came eery silence, for the _Pioneer's_ motor had gone dead. Ahead there was utter darkness. The liner and her convoy had completely vanished and the _Pioneer_ was slipping into a spin!

"What's up?" asked George of Hart, who was tugging frantically at the controls.