Looking up at an angle, between decks of clouds, she could dimly see the opposite floor of the chamber, bumped and ridged with a carpet of mysterious mechanism.

"No moving parts in the whole chamber except for large pumps, and not many of those," Lanier said. "The builders relied upon a built-in weather cycle. Rain falls, picks up heat, flows down channels into shallow ponds, evaporates, carries heat up, and the atmospheric maintenance systems drain it off, we're still not sure how."

"What does it all do?"

"When the Stone was first designed, the sixth chamber was going to be another city. But the builders had specified that the Stone could only accelerate at three percent g. Just before the Stone was outfitted—and before the completion of the major excavation—they found a way to allow the Stone to accelerate to the limit of its power. The method was complex and expensive, but it gave the Stone a versatility the builders couldn't pass up. So the sixth chamber was equipped with selective inertial damping machinery, which makes up a small fraction of what is here now." He nodded at the vista through the glass. "That's why none of the chamber floors are inclined, and none of the ponds or rivers are equipped with slop barriers. They don't need them. The sixth chamber can selectively damp the effects of inertia on any object in the Stone. On a large scale, it overcomes acceleration and deceleration of the entire ship. On a small scale, it prevents inertial effects in the trains. It's self-regulating, though we haven't found any 'brain' yet."

The rain hit the transparent roof and ran down the forty-five degree slope over the stairwell. Lanier paused to look at the beads and rivulets of water.

"Since that time, the machinery has been modified and expanded. It once covered about three square kilometers, and the rest of the sixth chamber was used for industry and research, things that couldn't be done in the cities. Now, it maintains the seventh chamber as well."

Four people, all clad in yellow rain gear, marched along the edge of the channel beyond the terminal. They had parked their truck a few meters away, on a raised roadbed.

"Our reception committee," Lanier said. They walked to the head of the staircase. Cold air pooled in the stairwell, and Patricia shivered as an outside gust blew some of it over them. Rain sang softly overhead. Between the rivulets on the glass, through a trench-like break in the clouds, Patricia saw the opposite northern cap. All the other caps had been virtually blank, featureless. This one was furrowed by a row of rectangular boxes, spaced at equal intervals like a steep flight of stairs. On the face of each box was an elliptical design. The boxes, she estimated, were at least a kilometer wide, and the ellipses half that along their major axis.

The first of the four to reach the top of the stairs doffed his rain cap. Patricia looked down to see her former professor, his face ruddy and bearded, eyes small and suspicious as if from some long-harbored hurt. Rimskaya was just as she remembered him. He returned her stare defensively, then nodded to Lanier. Behind him, a tall, even-featured blond woman and two Chinese, a man and a woman wearing green caps, removed their gear and shook water off onto the floor.