that it was the necessary first step toward interplanetary travel, with star ships yet to come. But most scientists wanted it, desperately, for their own ends. There were low-temperature experiments, electronic experiments, weather observations, star-temperature measurements, astronomical observations.... Any man in any field of science could name reasons for it to be built. Even the atom scientists had one, and nearly the best. Their argument was that there were new developments of nuclear theory that needed to be tried out, but should not be tried out on Earth. There were some reactions that ought to yield unlimited power for all the world from really abundant materials. But there was one chance in fifty that they wouldn’t be safe, just because the materials were so abundant. No sane man would risk a two-per-cent chance of destroying Earth and all its people, yet those reactions should be tried. In a space ship some millions of miles out in emptiness they could be. Either they’d be safe or they would not. But the only way to get a space ship a safe enough distance from Earth was to make a Space Platform as a starting point. Then a ship could shoot away from Earth with effectively zero gravity and full fuel tanks. The Platform should be built so civilization could surge ahead to new heights!

But despite these excellent reasons, it was the Platform’s enemies who really got it built. The American Congress would never have appropriated funds for a Platform for pure scientific research, no matter what peacetime benefits it promised. It was the vehemence of those who hated it that sold it to Congress as a measure for national defense. And in a sense it was.

These were ironic aspects Joe hadn’t thought about before, just as he hadn’t thought about the need to defend the Platform while it was being built. Defending it was Sally’s father’s job, and he wouldn’t have a popular time. Joe wondered idly how Sally liked living out where the most important job on Earth was being done. She was a nice kid. He remembered appreciatively that she’d grown up to be a very good-looking girl. He tended to remember her mostly as the tomboy who could beat him swimming, but the last time he’d seen her, come to think of it, he’d been startled to observe how pretty she’d grown. He didn’t know anybody who ought to be better-looking.... She was a really swell girl....

He came to himself again. There was a change in the look of the sky ahead. There was no actual horizon, of course. There was a white haze that blended imperceptibly into the cloud layer so that it was impossible to tell where the sky ended and the clouds or earth began. But presently there were holes in the clouds. The ship droned on, and suddenly it floated over the edge of such a hole, and looking down was very much like looking over the edge of a cliff at solid earth illimitably far below.

The holes increased in number. Then there were no holes at all, but only clouds breaking up the clear view of the ground beneath. And presently again even the clouds were left behind and the air was clear—but still there was no horizon—and there was brownish earth with small green patches and beyond was sere brown range. At seventeen thousand feet there were simply no details.

Soon the clouds were merely a white-tipped elevation of the white haze to the sides and behind. And then there came a new sound above the droning roar of the motors. Joe heard it—and then he saw.

Something had flashed down from nowhere. It flashed on ahead and banked steeply. It was a fighter jet, and for an instant Joe saw the distant range seem to ripple and dance in its exhaust blast. It circled watchfully.

The transport pilot manipulated something. There was a change in the sound of the motors. Joe followed the co-pilot’s eyes. The jet fighter was coming up astern, dive brakes extended to reduce its speed. It overhauled the transport very slowly. And then the transport’s pilot touched one of the separate prop-controls gently, and again, and again. Joe, looking at the jet, saw it through the whirling blades. There was an extraordinary stroboscopic effect. One of the two starboard propellers, seen through the other, abruptly took on a look which was not that of mistiness at all, but of writhing, gyrating solidity. The peculiar appearance vanished, and came again, and vanished and appeared yet again before it disappeared completely.

The jet shot on ahead. Its dive brakes retracted. It made a graceful, wallowing, shallow dive, and then climbed almost vertically. It went out of sight.

“Visual check,” said the co-pilot drily, to Joe. “We had a signal to give. Individual to this plane. We didn’t tell it to you. You couldn’t duplicate it.”

Joe worked it out painfully. The visual effect of one propeller seen through another—that was identification. It was not a type of signaling an unauthorized or uninformed passenger would expect.

“Also,” said the co-pilot, “we have a television camera in the instrument board yonder. We’ve turned it on now. The interior of the cabin is being watched from the ground. No more tricks like the phony colonel and the atom bomb that didn’t ‘explode.’”

Joe sat quite still. He noticed that the plane was slanting gradually downward. His eyes went to the dial that showed descent at somewhere between two and three hundred feet a minute. That was for his benefit. The cabin was pressurized, though it did not attempt to simulate sea-level pressure. It was a good deal better than the outside air, however, and yet too quick a descent meant discomfort. Two to three hundred feet per minute is about right.

The ground took on features. Small gulleys. Patches of coloration too small to be seen from farther up. The feeling of speed increased. After long minutes the plane was only a few thousand feet up. The pilot took over manual control from the automatic pilot. He seemed to wait. There was a plaintive, mechanical beep-beep and he changed course.

“You’ll see the Shed in a minute or two,” said the co-pilot. He added vexedly, as if the thing had been bothering him, “I wish I hadn’t missed that sandy-haired guy putting his hand in the wheel well! Nothing happened, but I shouldn’t have missed it!”

Joe watched. Very, very far away there were mountains, but he suddenly realized the remarkable flatness of the ground over which they were flying. From the edge of the world, behind, to the very edge of these far-distant hills, the ground was flat. There were gullies and depressions here and there, but no hills. It was flat, flat, flat....

The plane flew on. There was a tiny glimmer of sunlight. Joe strained his eyes. The sunlight glinted from the tiniest possible round pip on the brown earth. It grew as the plane flew on. It was half a cherry stone. It was half an orange, with gores. It was the top section of a sphere that was simply too huge to have been made by men.

There was a thin thread of white that ran across the dun-colored range and reached that half-ball and then ended. It was a highway. Joe realized that the half-globe was the Shed, the monstrous building made for the construction of the Space Platform. It was gigantic. It was colossal. It was the most stupendous thing that men had ever created.

Joe saw a tiny projection near the base of it. It was an office building for clerks and timekeepers and other white-collar workers. He strained his eyes again and saw a motor truck on the highway. It looked extraordinarily flat. Then he saw that it wasn’t a single truck but a convoy of them. A long way back, the white highway was marked by a tiny dot. That was a motor bus.

There was no sign of activity anywhere, because the scale was so great. Movement there was, but the things that