importantly.

Elshawe was trying to frame his next question when Porter said: "I know the name doesn't tell you much, but then, names never do, do they? You know what a transformer does, but what does the name by itself convey? Nothing, unless you know what it does in the first place. A cyclotron cycles something, but what? A broadcaster casts something abroad—what? And how?"

"I see. And the 'how' and 'what' is your secret, eh?"

"Partly. I can give you a little information, though. Suppose there were only one planet in all space, and you were standing on its surface. Could you tell if the planet were spinning or not? And, if so, how fast? Sure you could; you could measure the so-called centrifugal force. The same thing goes for a proton or electron or neutron or even a neutrino. But, if it is spinning, what is the spin relative to? To the particle itself? That's obvious nonsense. Therefore, what is commonly called 'inertia' is as much a property of so-called 'empty space' as it is a property of matter. My device simply utilizes spatial inertia by polarizing it against the matter inertia of the ship, that's all."

"Hm-m-m," said Elshawe. As far as his own knowledge of science went, that statement made no sense whatever. But the man's manner was persuasive. Talking to him, Elshawe began to have the feeling that Porter not only knew what he was talking about, but could actually do what he said he was going to do.

"What's that?" Porter asked sharply, looking up into the sky.

Elshawe followed his gaze. "That" was a Cadillac aircar coming over a ridge in the distance, its fans making an ever-louder throaty hum as it approached. It settled down to an altitude of three feet as it neared, and floated toward them on its cushion of air. On its side, Elshawe could see the words, UNITED STATES GOVERNMENT, and beneath that, in smaller letters, Civil Aeronautics Authority.

"Now what?" Porter muttered softly. "I haven't notified anyone of my intentions yet—not officially."

"Sometimes those boys don't wait for official notification," Elshawe said.

Porter glanced at him, his eyes narrowed. "You didn't say anything, did you?"

"Look, Mr. Porter, I don't play that way," Elshawe said tightly. "As far as I'm concerned, this is your show; I'm just here to get the story. You did us a favor by giving us advance notice; why should we louse up your show for you?"

"Sorry," Porter said brusquely. "Well, let's make a good show of it."

The CAA aircar slowed to a halt, its fans died, and it settled to its wheels.

Two neatly dressed, middle-aged men climbed out. Both were carrying briefcases. Porter walked briskly toward them, a warm smile on his face; Elshawe tagged along behind. The CAA men returned Porter's smile with smiles that could only be called polite and businesslike.

Porter performed the introductions, and the two men identified themselves as Mr. Granby and Mr. Feldstein, of the Civil Aeronautics Authority.

"Can I help you, gentlemen?" Porter asked.

Granby, who was somewhat shorter, fatter, and balder than his partner, opened his briefcase. "We're just here on a routine check, Mr. Porter. If you can give us a little information...?" He let the half-question hang in the air as he took a sheaf of papers from his briefcase.

"Anything I can do to help," Porter said.

Granby, looking at the papers, said: "In 1979, I believe you purchased a Grumman Supernova jet powered aircraft from Trans-American Airlines? Is that correct?"

"That is correct," Porter agreed.

Granby handed one of the papers to Porter. "That is a copy of the registration certificate. Is the registration number the same as it is on your copy?"

"I believe so," Porter said, looking at the number. "Yes, I'm sure it is."

Granby nodded briskly. "According to our records, the machine was sold as scrap. That is to say, it was not in an airworthy condition. It was, in fact, sold without the engines. Is that correct?"

"Correct."

"May I ask if you still own the machine in question?"

Porter gave the man a look that accused Granby of being stupid or blind or both. He pointed to the hulking fuselage of the giant aircraft. "There it is."

Granby and Feldstein both turned to look at it as though they had never noticed it before. "Ah, yes," Granby said, turning back. "Well, that's about all there is to it." He looked at his partner. "It's obvious that there's no violation here, eh, Feldstein?"

"Quite," said Feldstein in a staccato voice.

"Violation?" Porter asked. "What violation?"

"Well, nothing, really," Granby said, deprecatingly. "Just routine, as I said. People have been known to buy aircraft as scrap and then repair them and re-outfit them."

"Is that illegal?" Porter asked.

"No, no," said Granby hastily. "Of course not. But any ship so re-outfitted and repaired must pass CAA inspection before it can leave the ground, you understand. So we keep an eye on such transactions to make sure that the law isn't violated."

"After three years?" Porter asked blandly.

"Well ... ah ... well ... you know how it is," Granby said nervously. "These things take time. Sometimes ... due to ... clerical error, we overlook a case now and then." He glanced at his partner, then quickly looked back at Porter.

"As a matter of fact, Mr. Porter," Feldstein said in a flat, cold voice, "in view of your record, we felt that the investigation at this time was advisable. You bought a scrap missile and used it illegally. You can hardly blame us for looking into this matter."

"No," said Porter. He had transferred his level gaze to the taller of the two men, since it had suddenly become evident that Feldstein, not Granby, was the stronger of the two.

"However," Feldstein went on, "I'm glad to see that we have no cause for alarm. You're obviously not fitting that up as an aircraft. By the way—just out of curiosity—what are you doing with it?" He turned around to look at the big fuselage again.

Porter sighed. "I had intended to hold off on this for a few days, but I might as well let the cat out now. I intend to take off in that ship this week end."

Granby's eyes opened wide, and Feldstein spun around as though someone had jabbed him with a needle. "What?"

Porter simply repeated what he had said. "I had intended to make application to the Space Force for permission to test it," he added.

Feldstein looked at him blankly for a moment.

Then: "The Space Force? Mr. Porter, civilian aircraft come under the jurisdiction of the CAA."

"How's he going to fly it?" Granby asked. "No engines, no wings, no control surfaces. It's silly."

"Rocket motors in the rear, of course," said Feldstein. "He's converted the thing into a rocket."

"But the tail is closed," Granby objected. "There's no rocket orifice."

"Dummy cover, I imagine," Feldstein said. "Right, Mr. Porter?"

"Wrong," said Porter angrily. "The motive power is supplied by a mechanism of my own devising! It has nothing to do with rockets! It's as superior to rocket power as the electric motor is to the steam engine!"

Feldstein and Granby glanced at each other, and an almost identical expression of superior smugness grew over their features. Feldstein looked back at Porter and said, "Mr. Porter, I assure you that it doesn't matter what you're using to lift that thing. You could be using dynamite for all I care. The law says that it can't leave the ground unless it's airworthy. Without wings or control surfaces, it is obviously not airworthy. If it is not a rocket device, then it comes under the jurisdiction of the Civil Aeronautics Authority, and if you try to take off without our permission, you'll go to jail.

"If it is a rocket device, then it will be up