Ito showed Dura a plaque on the wall, inscribed with text on the display. " 'The structure is fractal.' " Ito pronounced the word carefully. " 'That is, it shows a similar structure on many scales. Corestuff lends itself to this property, being composed of hyperons, bags of quarks in which are dissolved the orderly nucleons — the protons and neutrons — of the human world.

" 'In regions humans can inhabit Corestuff exists in large metastable islands of matter — the familiar Corestuff bergs retrieved by Fishermen, and used to construct anchor-bands, among other artifacts...

" 'But further in, in the deep Core, the hyperonic material can combine to form extraordinary, rich structures like this model. The representation here is based on guesswork — on fragmentary tales from the time of the Core Wars, and on half-coherent accounts of Fishermen. Nevertheless, the University scholars feel that...' "

"But," Dura interrupted, "what is it?"

Ito turned to her, her face round and smooth in the dim light. "Why, it's a Colonist," she said.

"But the Colonists were human."

"No," Ito said. "Not really. They abandoned us, stealing our machines, and went down into the Core." She looked somber. "And this is what they became. They lived in these structures of Corestuff."

Dura stared into the deep, menacing depths of the model. It was as if, here in the belly of the City, she had been transported to the Core itself and left to face this bizarre, monstrous entity alone.

8

CLUTCHING HIS SURFBOARD, Cris led Farr through the heart of the City.

They followed a tangle of subsidiary streets, avoiding the main routes. Farr tried to memorize their path, but his rudimentary sense of City-bound direction was soon overwhelmed. Lost, baffled, but following Cris doggedly, he involuntarily glanced around, looking for the Quantum Sea, the angle of the vortex lines to orient himself. But of course, here deep in the guts of Parz, the faceless wooden walls hid the world.

After a time, though, he realized that they must have passed below the City's rough equator and moved into the region called the Downside. The walled streets here were meaner, with illumination shafts and wood-lamps far separated. There were few cars and fewer Wavers, and the doors to dwelling-places off the Downside streets, battered and dirty, looked impenetrably solid. Cris didn't comment on the changed environment — he kept up his chatter of Surfing as if oblivious — but Farr noticed how the City boy kept his precious board clutched tight against his chest, shielding it with his body.

At length they came to a wide, oval port set in a street wall. The shaft beyond this port, about ten mansheights across, was much plainer than any City street — long and featureless, and with scuffed, unfinished-looking walls — but it led, Farr saw, to an ellipse of clear, precious Airlight. He stared hungrily into that light, marveling at how the bright yellow glow glittered from scraped-smooth patches of wall.

"Are we going down here?"