She looked. The air was clear. Visibility was at least thirty kilometers. The northern cap seemed to be obscured, not nearly as obvious as the looming gray presence in the other chambers. She looked up and squinted, trying to make out the end of the plasma tube.

It didn't end. It went on, certainly more than thirty kilometers, getting dimmer and thinner until it almost merged with the horizon.

Of course, on a non-curved surface—as the cylinders were, viewed parallel to the axis—the horizon was much higher. Given unlimited distance, the horizon would begin at a true vanishing point in the perspective. . .

"This chamber's longer," she said.

"Yes," Wu agreed cautiously. Chang nodded, grinning as if at some joke, her hands folded demurely in her lap.

"Now, let me get this straight. We've traveled about two hundred and twenty kilometers into the Stone, which is about two hundred and ninety kilometers long. So this chamber could be, maybe, fifty kilometers across." Her hands were trembling. "But it isn't."

"Look closely," Lanier said.

"It's an optical illusion. I can't see the northern cap."

"No," Farley said, all too sympathetic.

"So?" Patricia looked around the cab. The others kept their faces impassive, except for Chang's secretive smile. "What the hell am I supposed to see?"

"You tell us," Lanier said.

She figured furiously in her head, looking up at the opposite side of the chamber, trying to calculate distances in the strange perspective of the huge cylinders. "Stop the truck."

Farley brought the vehicle to a halt and Patricia descended from the cab to stand on the roadway. Then she clambered up a ladder to a platform on top of the cab and looked down the straight line of the road. The road went to its own vanishing point—no cap, no barrier. Above, the rest of the landscape did much the same.

"It's bigger," she said. Farley and Lanier stood by the truck, looking up at her. Wu and Chang joined them. "It's bigger than the asteroid. It goes beyond the end. Is that what you're trying to tell me?"

"We don't tell," Lanier said. "We show. It's the only way."

"You're trying to tell me it doesn't stop, it goes right on out the other end?" She heard the touch of panic and high-pitched fascination in her own voice.

The Stanford professor, six years before, had been wrong. Someone besides extraterrestrials and gods could appreciate her work. She now knew why she had been brought up from Vandenberg, carried to the Stone by shuttle and OTV.

The asteroid was longer on the inside than it was on the outside.

The seventh chamber went on forever.

Chapter Five

Patricia had slept—she checked her watch—nine hours. She lay on the cot, listening to the gentle sound of tent canvas clapping in the breeze.

In at least this region of the seventh chamber, there was little need for solid-walled buildings. The weather was dry and mild, the air temperature warm. She stared up at the awning stretched between aluminum poles, at the smoky outline of the plasma tube through the cloth.