by-your-own-bootstraps maneuver...."

"An inventor," said Artie, quoting his favorite self-coined aphorism, "must never think like a scientist!"

"But"—I said, more to stem the tide I expected than to really make a coherent objection.

"An inventor," he went dreamily onward, "is essentially a dreamer; a scientist is an observer. An inventor tries to make a result he wants happen; a scientist tries to tell the inventor that the result cannot be achieved."

"Please. Artie. Don't tell me about the bee again."

But Artie told me about the bumblebee, and how there were still some scientists who insisted, according to the principles of aerodynamics, that it was not constructed properly to enable it to fly. And about how men of this short-sighted ilk were still scoffing at the ancient alchemist's talk of the Philosopher's Stone for transmuting metals, even though transmutation of metals was being done every day in atomic piles. And how he'd theorized that there was once a genuine Philosopher's Stone, probably a hunk of pure U-235, that someone had managed to make, which might explain why so many alchemists (lacking, unfortunately, any knowledge of heavy radiations or Geiger counters) sort of died off in their quest for the stone.

It was nearly lunchtime when he finished his spiel, and I was kicking myself in my short-memoried brain for having let him get onto the subject, when abruptly the joyous glow behind his eyes damped its sparkle a bit.

"There is one little hitch—"

"I thought it looked too easy," I sighed, waiting for the clinker. "Don't tell me it has to be made out of pure Gallium, which has the regrettable tendency to liquiefy at about thirty degrees centigrade? Or perhaps of the most elusive of its eleven isotopes?"

"No, no, nothing like that," he murmured almost distractedly. "It's the force-per-gram part that's weak."

"Don't tell me," I said unhappily, "that this thing'll only generate enough force to lift itself?"

A feeble ghost of his erstwhile grin rode briefly across his lips. "That's the way it works out on paper," he said.

"Which means," I realized aloud, "that it's commercially useless, because what's the good of an anti-gravity machine that can't lift anything except itself! It falls into the class of lifeboats that float up to the gunwales in the water while still empty. Fun to watch, but impossible to use. Hell, Artie, if that's the setup, then this thing wouldn't be any more help to a space-aiming government than an aborigine's boomerang; it flies beautifully, but not if the aborigine tries to go with it."

"However," he said, a bit more brightly, "I've been wrong on paper before. Remember the bumblebee, Burt! That theory still holds up on paper. But the bee still flies."

He had me, there. "So you want I should build it anyhow, just on the off-chance that it won't follow the rules of physical logic, and will decide to generate a force above and beyond its own gravitic drag?"

"That's it," he said happily. "And even if it only manages to negate its own weight, we'll have an easier time ironing the bugs out of a model than we would out of a diagram. After all, who'd have figured that beyond Mach I, all the lift-surfaces on a plane work in reverse?"

It wasn't, I had to admit, anything that an inventor could have reasonably theorized at the outset.... So I locked myself in the lab for a week, and built his gadget, while he spent his time pacing through his fourteen-room mansion across the way from the lab building (the "way" being the flat grassy region on Artie's estate that housed his swimming pool, private heliport, and movie theatre), trying to coin a nifty name for the thing. We both finished in a dead heat.

I unlocked the door of the lab, blinked hard against the sting of warm yellow sunlight after a week of cool blue fluorescents, and just as I wheezed, "Got it," Artie was counterpointing with, "We'll call it The Uuaa!" (He made four syllables out of it.)

"The Oo-oo-ah-ah?" I glottaled. "In honor of the fiftieth state, or what? I know 'aa' is a type of lava, but what the hell's 'uu', besides the noise a man makes getting into an overheated bath?"

Artie pouted. "'Uuaa' is initials. For 'Up, up, and away!' I thought it was pretty good."

I shook my head. "Why feed free fodder to the telecomics? I can hear them now, doing monologues about people getting beri-beri flying from Walla Walla to Pago Pago on their Uuaas...."

"So what would you call it!" he grunted.

"A bust," I sighed, left-thumbing over my shoulder at the lab. "It sits and twirls and whistles a little, but that's about the size of it, Artie."

He spanieled with his eyes, basset-hounded with his mouth, and orangutaned with his cheeks, then said, with dim hope, "Did you weigh it? Maybe if you weighed it—"

"Oh, it lost, all right," I admitted. "When I connected the batteries, the needle on the scale dropped down to zero, and stopped there. And I found that I could lift the machine into the air, and it'd stay where it was put, just whistling and whirling its cones. But then it started to settle." I beckoned him back inside.

"Settle? Why?" Artie asked.

"Dust," I said. "There's always a little dust settling out of the air. It doesn't weigh much, but it made the machine weigh at least what the dust-weight equalled, and down it went. Slow and easy, but down."

Artie looked at the gadget, sitting and whistling on the floor of the lab, then turned a bleak-but-still-hopeful glance my way. "Maybe—If we could make a guy take on a cone-shape, and whirled him—"

"Sure," I muttered. "Bend over, grab his ankles, and fly anywhere in the world, with his torso and legs pivoting wildly around his peaked behind." I shook my head. "Besides the manifestly undignified posturing involved, we have to consider the other effects; like having his eyeballs fly out."

"If—If we had a bunch of men lie in a circle around a kind of Maypole-thing, each guy clutching the ankles of the next one...."

"Maybe they'd be weightless, but they still wouldn't go up," I said. "Unless they could be towed, somehow. And by the time they landed, they'd be too nauseous to be of any use for at least three days. Always assuming, of course, that the weak-wristed member of the sick circlet didn't lose his grip, and have them end up playing mid-air crack-the-whip before they fell."

"So all right, it's got a couple of bugs!" said Artie. "But the principle's sound, right?"

"Well—Yeah, there you got me, Artie. The thing cancels weight, anyhow...."

"Swell. So we work from there," He rubbed his hands together joyously. "And who knows what we'll come up with."

"We never do, that's for sure," I mumbled.

But Artie just shrugged. "I like surprises," he said.

The end of the day—me working, Artie inventing—found us with some new embellishments for the machine. Where it was originally a sort of humped metal box (the engine went inside the hump) studded with toothbrush-bristle rows of counter-revolving cones (lest elementary torque send the machine swinging the other way, and thus destroy the thrust-effect of the cones), it now had an additional feature: A helical flange around each cone.

"You see," Artie explained, while I was torching them to order from plate metal, "the helices will provide lift as the cones revolve."

"Only in the atmosphere of the planet," I said.

"Sure, I know. But by the time the outer limits of the air are reached, the machine, with the same mass-thrust, will have less gravity-drag to fight, being that much farther from the Earth. The effect will be cumulative. The higher it gets, the more outward thrust it'll generate. Then nothing'll stop it!"

"You could be right," I admitted, hammering out helix after helix on an electric anvil (another