"It sure feels that old," Bill agreed. "I know something of the complexities involved in maintaining a biosystem," Gaby went on. "Gaea is larger than O'Neil One, and that makes her more flexible. But in a few centuries things would break down without control. Things have not broken down completely."

"It could be robots," Bill said. "That's fine with me," Cirocco said. "As long as there's some intelligence behind this, I plan to contact it and ask for help. Computers might be easier to deal with."

Bill, who had read a great deal of science fiction, could make a dozen theories about any aspect of Gaea. He was partial to the ever-reliable plague mutation: something that came out of nowhere and killed enough of the builders to leave Gaea in the hands of automatic safety devices.

"She's a derelict, I'll bet on it," he told them. "Just like the ship from Heinlein's Orphans of the Sky. A lot of people set out in Gaea thousands of years ago and lost control on the way. The ship's computer put it in orbit around Saturn, shut down the engines, and is still up there keeping the air pumping and waiting for more orders."

They took a different route out, partly because it was impossible to tell how they had come in. Cirocco did not worry because as long as they went toward the light they were all right.

They reached the sunlight at a point far to the north of where they had gone in, and now could see something that had been concealed at their point of entry by the cable itself. It was a broken strand, but this one was on the ground.

Cirocco's first thought was of the giant sandworm Calvin had described. The strand looked like a living thing, shining in the

yellow light. Then she recalled the Brazilian pipelines she had seen on survival training: great silver tubes that knifed through the rain forest as if it were a contemptible obstacle.

The strand had cleared its own path when it fell, bringing down the tallest trees, crashing inexorably to the ground. The jungle had closed over it since that time, but the great mass still looked as if it could rise at any moment and shake off the encroaching vines, turning the trees into matchsticks.

Five hundred meters above, the severed upper end of the strand curled away from the body of the cable. It was ragged, and the inside revealed by the break glistened and threw back reflections of red and blue-green and tarnished copper. Gray discolorations like bread mold grew in the stump, and from the bottom a waterfall went straight down to a clump of vegetation widely separated from the forest. The volume of water was substantial and noisy, but issuing from the huge and twisted strand it looked like nothing more than a drip from a broken pipe.

They approached the fallen strand, found it to be composed of an array of hexagonal facets only a few millimeters across, cloudy with swirls of gold just beneath the surface. it threw back dull, broken reflection,, as if they were using the eye of a giant insect for a mirror.

They followed it down the hill and into the jungle, where the broken end turned out to be hollow but so clogged with brush and vines that entering it was impossible.

"Whatever was inside, the plants like it," Gaby said.

Cirocco said nothing. The advanced state of decay was de- pressing. The strand's open end was big enough to have flown Ringmaster right through it. It was a small thing on the stale of Gaea, only one of 200 strands in this cable alone. And yet it was such a towering wreck, going so quickly to rot and dissolution. When it parted, the whole surface of Gaea must have twanged in sympathy.

And no one had done anything about it.

She said nothing, but it was hard to look at the remains and feel there was someone still watching the machines.