He found himself sighing.

"What's the matter with you?"

He grinned ruefully at Jaen. "Sorry. It's just… I've been here such a short time, and I seem to have learned so little."

She frowned. "I thought you were getting some kind of crammer classes from Cipse and Grye."

"Not really," he admitted. "I guess I can see their point of view. I wouldn't want to waste time on a stowaway who is liable to be dumped back home within a few shifts."

She scratched her nose. "That might be the reason. But the two of them have never been shy of parading their knowledge in front of me. Rees, you ask damn hard questions. I suspect they're a little afraid of you."

"That's crazy—"

"Let's face it, most of those old buggers don't know all that much. Hollerbach does, I think; and one or two others. But the rest just follow the ancient printouts and hope for the best. Look at the way they patch up the ancient instruments with wood and bits of string… They'd be lost if anything really unexpected happened — or if anyone asked them a question from a strange angle."

Rees thought that over and reflected how far his view of the Scientists had shifted since his arrival here. Now he saw that they were frail humans like himself, struggling to do their best in a world growing shabbier. "Anyway," he said, "it doesn't make a lot of difference. Every time I open my eyes I see questions that don't get answered. For instance, on every page of Cipse's numbers books is written 'IBM.' What does that mean?"

She laughed. "You've got me there. Maybe it's something to do with the way those books were produced. They come from the Ship, you know."

His interest quickened. "The Ship? You know, I've heard so many stories about that I've no idea what's true."

"My understanding is that there really was a Ship, It was broken up to form the basis of the Raft itself."

He pondered that. "And the original Crew printed those books?"

She hesitated, obviously near the limits of her knowledge. "They were produced a few generations later. The first Crew had kept their understanding in some kind of machine."

"What machine?"

"… I don't know. Maybe a talking machine, like the buses. The thing was more than a recording device, though. It could do calculations and computations."

"How?"

"Rees," she said heavily, "if I knew that I'd build one. OK? Anyway, with the passing of time the machine began to fail, and the crew were afraid they wouldn't be able to continue their computations. So, before it expired, the machine printed out everything it knew. And that includes an ancient type of table called 'logarithms' to help us do calculations. That's what Cipse was lugging in

to the Bridge. Maybe you'll learn how to use logarithms, some day."

"Yeah. Maybe."

The bus rolled out of the thicket of cables; Rees found himself squinting in the harsh light of the star poised above the Raft.

Jaen was saying, "You understand Cipse's job, do you?"

"I think so," he said slowly. "Cipse is a Navigator. His job is to work out where the Raft should move to."

Jaen nodded. "And the reason we have to do that is to get out of the path of the stars falling in from the rim of the Nebula." She jerked a thumb at the glowing sphere above. "Like that one. In the Bridge they keep records of approaching stars, so they can move the Raft in plenty of time. I reckon we'll be shifting soon… That's a sight to see, Rees; 1 hope you don't miss it. All the trees tilting in unison, the rush of wind across the deck — and if I get through my appraisal I'll be working on the moving team."

"Good for you," he said sourly.

With a sudden seriousness she patted his arm. "Don't give up hope, miner. You're not off the Raft yet."

He smiled at her, and they spent the rest of the journey in silence.

The bus reached the edge of the Raft's gravity well. The Rim approached like a knife edge against the sky, and the bus strained to a halt beside a broad stairway. Rees and Jaen joined a queue of passengers before a supply dispenser. An attendant sat sullenly beside the machine, silhouetted against the sky; Rees, staring absently, found him vaguely familiar.

The supply machine was an irregular block as tall as two men. Outlets pierced its broad face, surrounding a simple control panel reminiscent to Rees of the Mole's. On the far side a nozzle like a huge mouth strained outwards at the atmosphere of the Nebula; Rees had learned that the machine's raw material was drawn in by that nozzle from the life-rich air, and it wasn't hard to imagine the machine taking huge breaths through those metal lips.

Jaen murmured in Ms ear: "Powered by a mini black hole, you know."

He jumped. "A what?"

She grinned, "You don't know? I'll tell you later."

"You enjoy this, don't you?" he hissed.

Away from the shelter of the flying forest the starlight from above was intense. Rees found sweat droplets trickling into his eyes; he blinked, and found himself staring at the broad neck of the man in front of him. The flesh was studded with coarse black hair and was glistening damp near the collar. The man raised a wide, pug face to the star. "Damn heat," he grunted. "Don't know why we're still sitting underneath the bloody thing. Mith ought to get off his fat arse and do something about it. Eh?" He glared inquisitively at Rees.

Rees smiled back uncertainly. The man gave him a strange look, then turned away.

After uncomfortable minutes the queue cleared, passengers squeezing past them down the stairs with their packets of food, water and other materials. Watched by the sullen attendant, Rees and Jaen stepped up to the machine; Jaen began to tap into the control panel one of the Scientists' registration numbers, and then a complex sequence detailing their requirements. Rees marveled at the way her fingers flew over the keyboard — yet another skill he might never get the chance to learn…

And he became aware that the attendant was grinning at him. The man sat on a tall wooden stool, arms folded; black stripes were stitched into his shabby coverall. "Well, well," he said slowly. "It's the mine rat."

"Hello, Gover," Rees said stiffly.

"Still skivvying for those old farts in Science, eh? I'd have thought they'd chuck you into the nozzles by now. All you mine rats are good for…"

Rees found his fists clenching; his biceps bunched almost painfully.

"So you're still the same nasty piece of work, eh, Gover?" Jaen snapped. "Getting thrown out of Science hasn't helped your character development, then,"

Gover bared yellow teeth. "I chose to leave. I'm not spending my life with those useless old space-wasters. At least with Infrastructure I'm doing real work. Learning real skills."

Jaen lodged her fists on her hips. "Gover, if it wasn't for the Scientists the Raft would have been destroyed generations ago."

He sniffed, looking bored. "Sure. You keep believing it."

"It's the truth."

"Maybe once. But what about now? Why haven't they moved us out from under that thing in the sky, then?"

Jaen took an angry breath… then hesitated, having no easy answer.

Gover didn't seem interested in his small victory. "It doesn't matter. Think what you want. The people who really keep this Raft flying — Infrastructure, the woodsmen, the carpenters and metalworkers — we are going to be heard before long. And that will be the start of the long drop for all the

parasites."

Jaen frowned. "What's that supposed to mean?"

But Gover had turned away, smiling cynically; and a man behind them growled, "Come on; move it, you two."

They returned to the bus clutching pallets of supplies. Bees said, "What if he's right, Jaen? What if the Scientists, the Officers are — not allowed to work any more?"

She shivered. "Then it's the end of the Raft. But I know Gover; he's just puffing up his own importance, to make us think he's happy with his move to Infrastructure. He's always been the same."