"We wouldn't put it like that ... They do need organic material. In the wild, you know, down on the Lowland, they preyed on humans. We do let them take our corpses. Why not?" He stroked a wall himself. "It means the Buildings are made of us, us, our ancestors. Sometimes people have to die inside a Building. The Weapon decrees it." our ancestors. Sometimes people have to die inside a Building. The Weapon decrees it."

"Why?"

"It seems to be studying Effigies. It thinks that the construction material of which Buildings are made excludes Effigies. Some of us are born inside Buildings, so no Effigy can enter us then. Others die within a Building, a special one we call the Morgue, in an attempt to trap the Effigies when they are driven out of their bodies.My own aunt died recently, and had to be taken inside the Morgue, but no Effigy was released."

"It seems very strange to us," Mina said cautiously. "To Shelf folk, I mean. That here you are living out your lives on a machine, made by another machine."

"It's not as if we have a choice," Telni said, feeling defensive. "We aren't allowed to leave."

She looked down at her feet, which were clad in sensible leather shoes not spindling, like Telni's. "I think you can tell that a machine built this place. It lacks a certain humanity." She glanced at him uncertainly. "Look, I'm speaking as a Philosopher. I myself am studying geology. The way time stratification affects erosion, with higher levels wearing away faster than the low, and the sluggish way rivers flow as they head down into the red..." She wasn't concentrating on what she was saying, but inspecting her surroundings. "For instance there's the thinness of this floor. On the Shelf we all grew up on a cliff-top. But here we are suspended in the air on a paper-thin sheet! Logically, perhaps, we're even safer here than standing on the Shelf. But it doesn't feel feel safe. A human designer would never have done it like this." safe. A human designer would never have done it like this."

"We live as best we can."

"I'm sure."

He took her to the very center of the Platform, and the wheel that turned as always, drawn by teams of patient spindlings. The cargo jockeys, unloading buckets and pallets of supplies drawn up from the Lowland, stared with curiosity as MinaAndry patted the necks of the laboring beasts. "How charming these beasts are! You know that on the Shelf they were driven to extinction during the War of the Cities. We are slowly restocking with animals drawn up from the Lowland herds, but it's ferociously expensive..."

Something about the way she patted and stroked the tall, elegant creatures moved Telni, deep inside. But he had to pull her aside when he saw a spindling was ready to cough; spindlings lacked a.n.u.ses and vomited their s.h.i.t from their mouths. Mina was astonished at the sight.

Anyhow, he hadn't brought her here for spindlings. He took Mina's hand and led her to the center of the Hub, close to the great hatch in the floor of the Platform, which revealed the cables that dangled down to the Lowland far below.

Mina squealed and drew back. "Oh! I'm sorry. Vertigo what a foolish reaction that is!"

"But evidently a very ancient one. Look." He pointed down through the hole. "I brought you here to see my own work. I earn my living through my studies with an apothecary. But this this is my pa.s.sion..." is my pa.s.sion..."

Holding tight to the rail, pushing a stray strand of hair back from her face, she peered down through the floor. From here, Telni's cradles of pendulums, of bobs and weights and simple control mechanisms, were clearly visible, attached in a train along one of the guide ropes that tethered the Platform to the Lowland plain.

"Pendulums?"

"Pendulums. I time their swing. From here I can vary the length and amplitude..." He showed her a rigging-up of levers he had fixed above the tether's anchor. "Sometimes there's a snag, and I go down in a harness, or send one of the cargo jockeys."

"How do you time them?"

"I have a clock the Weapon gave me. I don't understand how it works," he said, and that admission embarra.s.sed him. "But it's clearly more accurate than any clock we have. I have the pendulums spread out over more than a quarter of a kilometer. There's no record of anybody attempting to make such measurements over such a height difference. And by seeing how the period of the pendulums vary with height, what I'm trying to measure is "

"The stratification of time. The higher up you raise your pendulums, the faster they will swing." She smiled. "Even a geologist understands that much. Isn't it about five percent per meter?"

"Yes. But that's only a linear approximation. With more accurate measurements, I've detected an underlying curved function..." The rate at which time flowed faster, Telni believed, was inversely proportional to the distance from the center of Old Earth. "It only looks looks linear, simply proportional to height, if you pick points close enough together that you can't detect the curve. And an inverse relationship makes sense, because that's the same mathematical form as the planet's gravitational potential, and time stratification is surely some kind of gravitational effect..." He hoped this didn't sound naive. His physics, based on the philosophies extracted from Foro centuries ago with the Platform's first inhabitants, was no doubt primitive compared to the teachings Mina had been exposed to. linear, simply proportional to height, if you pick points close enough together that you can't detect the curve. And an inverse relationship makes sense, because that's the same mathematical form as the planet's gravitational potential, and time stratification is surely some kind of gravitational effect..." He hoped this didn't sound naive. His physics, based on the philosophies extracted from Foro centuries ago with the Platform's first inhabitants, was no doubt primitive compared to the teachings Mina had been exposed to.

Mina peered up at a sky where an unending storm of star clouds pa.s.sed, brightly blueshifted. "I think I understand," she said. "My mathematics is rustier than it should be. That means that the time distortion doesn't keep rising on and on. It comes to some limit."

"Yes! And that asymptotic limit is a distortion factor of around three hundred and twenty thousand compared to the Shelf level, which we've always taken as our benchmark. Actually, it corresponds to the five percent rule applied across the radius of Old Earth. So one year here corresponds to nearly a third of a million years, up there in the sky."

"Or," she said, "one year out there "

"Pa.s.ses in about a hundred seconds on the Self. We are falling into the future, Mina! Some believe that once Earth was a world without this layering of time, a world like many others, perhaps, hanging among the stars. And its people were more or less like us. But Earth came under some kind of threat. And so the elders of Earth pulled a blanket of time over their world and packed it off to the future: Earth is a jar of time, stopped up to preserve its children."

"That's all speculation."

"Yes. But it would explain such a high rate. And, Mina, I think this rate should be observable. The interval we call a 'year' is just a counting-up of days, but it's thought to be a folk memory of what was a real real year, the time it took Old Earth to circle its sun. We can't distinguish that sun, whatever is left of it. But we ought to be able to see the stars shifting back and forth, every hundred seconds, as we turn around the sun. I'm trying to encourage the astronomers to look for this, but they say they're too busy mapping other changes." He waved a hand at the sky. "Those chains of stars " year, the time it took Old Earth to circle its sun. We can't distinguish that sun, whatever is left of it. But we ought to be able to see the stars shifting back and forth, every hundred seconds, as we turn around the sun. I'm trying to encourage the astronomers to look for this, but they say they're too busy mapping other changes." He waved a hand at the sky. "Those chains of stars "

"They evolve faster than seen from Foro," she breathed, her upturned face bathed in the shifting blue starlight.

"They are not as previous generations witnessed them. Something new in the sky. However if the astronomers could could be persuaded to measure the external year, it would confirm my mathematics ... I'm always trying to improve my accuracy. The pendulums need to be long enough to give a decent period, but not too long or else the time stratification becomes significant be persuaded to measure the external year, it would confirm my mathematics ... I'm always trying to improve my accuracy. The pendulums need to be long enough to give a decent period, but not too long or else the time stratification becomes significant even over the length of the pendulum itself, even over the length of the pendulum itself, and the physics gets very complicated " and the physics gets very complicated "

She slipped her hand into his. "It's a wonderful discovery. n.o.body before, maybe not since the last Caress, has worked out how fast we're all plummeting into the future."

He flushed, pleased. But something made him confess, "I needed the Weapon's clock to measure the effects. And it set me asking questions about time in the first place."

"It doesn't matter what the Weapon did. This is your work. You should be happy."

"I don't feel happy," he blurted.

She frowned. "Why do you say that?"

Suddenly he was opening up to her in ways he'd never spoken to anybody else. "Because I don't always feel as if I fit. fit. As if I'm not like other people." He looked at her doubtfully, wondering if she would conclude he was crazy. "Maybe that's why I'm turning out to be a good Philosopher. I can look at the world from outside, and see patterns others can't. Do you ever feel like that?" As if I'm not like other people." He looked at her doubtfully, wondering if she would conclude he was crazy. "Maybe that's why I'm turning out to be a good Philosopher. I can look at the world from outside, and see patterns others can't. Do you ever feel like that?"

Still holding his hand, she walked him back to the wheel and stroked a spindling's stubby mane, evidently drawing comfort from the simple physical contact. "Sometimes," she said. "Maybe everybody does. And maybe it's a reaction to the unnatural environment of the Platform. But the world is as it is, and you just have to make the best of it. Do you get many birds up here?"

"Not many. Just caged songbirds. Hard for them to find anywhere to nest."

"I used to watch birds as a kid. I'd climb up to a place we call the Attic ... The birds use the time layers. The parents will nest at some low level, then go gathering food higher up. They've worked out they can take as long as they like, while the babies, stuck in slow time, don't get too hungry and are safe from the predators. Of course the parents grow old faster, sacrificing their lives for their chicks."

"I never saw anything like that. I never got the chance." He shook his head, suddenly angry, resentful. "Not on this island in the sky, a creature of some machine. Sometimes I hope the next Caress comes soon and smashes everything up."

She took both his hands and smiled at him. "I have a feeling you're going to be a challenge. But I like challenges."

"You do?"

"Sure. Or I wouldn't be here, spending a month with a bunch of old folk while seventeen months pa.s.s at home. Think of the parties I'm missing!"

His heart hammered, as if he had been lifted up into the blue. "I've only known you hours," he said. "Yet I feel "

"You should return to your work." The familiar child's voice was strange, cold, jarring.

Telni turned. The Weapon was here, hovering effortlessly over the hole in the floor. His tethered boy stood some meters away, tense, obviously nervous of the long drop. The spindlings still turned their wheel, but the cargo jockeys stood back, staring at the sudden arrival of the Weapon, the maker and ruler of the world.

Telni's anger flared. He stepped forward towards the child, fists clenched. "What do you want?"

"We have come to observe the formal congress this evening. The Philosophers from Shelf and Platform. There are many questions humans can address which we "

"Then go scare all those old men and women. Leave me alone." Suddenly, with Mina at his side, he could not bear to have the Weapon in his life, with its strange ageless boy on his umbilical. "Leave me alone, I say!"

Powpy turned to look at Mina. "She will not stay here. This girl, MinaAndry. Her home is on the Shelf. Her family, the Andry-Feri, is an ancient dynasty. She has responsibilities, to bear sons and daughters. That is her destiny. Not here."

"I will stay if I wish," Mina said. She was trembling, Telni saw, evidently terrified of the Weapon, this strange, ancient, wild machine from the dark Lowland. Yet she was facing it, answering it back.

Telni found himself snarling, "Maybe she'll bear my my sons and daughters." sons and daughters."

"No," said the boy.

"What do you mean, no?"

"She is not suitable for you."

"She's a scholar from Foro! She's from the stock you brought here in the first place."

'It is highly unlikely that she has an Effigy, as few in her family do. Your partner should have an Effigy. That is why '

"Selective breeding," Mina gasped. "It's true. This machine really is breeding humans like cattle..."

"I don't care about Effigies," Telni yelled. "I don't care about you and your stupid projects." He stalked over to the boy, who stood trembling, clearly afraid, yet unable to move from the spot.

"Telni, don't," Mina called.

The boy said calmly, "Already you have done good and insightful work, which "

Telni struck, a hard clap with his open hand to the side of the boy's head. Powpy went down squealing.

Mina rushed forward and pushed herself between Telni and the boy. "What have you done?"

"He it all my life "

"Is that this boy's fault? Oh, get away, you fool." She knelt down and cradled the child's head on her lap. With the umbilical still dangling from the back of his neck, Powpy was crying, in a strange, contained way. "He's going to bruise. I think you may have damaged his ear. And his jaw no, child, don't try to talk." She turned to the Weapon, which hovered impa.s.sively. "Don't make him speak for you again. He's hurt."

Telni opened his hands. "Mina, please "

"Are you still here?" she snarled. "Go get help. Or if you can't do that, just go away. Go!"

He knew he had lost her, in this one moment, this one foolish blow.

He turned away and headed towards the Platform's hospital to find a nurse.

The little boy walked into Telni's cell, trailing a silvery rope from the back of his neck.

Telni was huddled up his bunk, a spindling-skin blanket over his body. He was shivering, drying out, not for the first time. He scowled at the boy. "You again."

"Be fair," the boy said. "We have not troubled you for twenty years."

"Not for you." His figuring was cloudy. "Down on Lowland, less than a year "

"This boy is not yet healed."

Telni saw his face was distorted on the right hand side. "I apologize." He sat up. "I apologize to you you what in the blue was your name?" what in the blue was your name?"

"Powpy."

"I apologize to you, Powpy. Not to the thing that controls you. Where is it, by the way?"

"It would not fit through the door."

He lay back and laughed.

"We did not expect to find you here."

"In the drunk tank? Well, I got fired by the apothecary for emptying her drugs cabinet one too many times. So it was the drink for me." He patted his belly. "At least it's putting fat on my bones."

"Why this slow self-destruction?"

"Call it an experiment. I'm following in my father's footsteps, aren't I? After all, thanks to you, I have no more chance of happiness, of meaning in my life, than he did. And besides, it's all going to finish in a big smash soon, isn't it? As you smart machines no doubt know already."

It didn't respond to that immediately. "You never had a wife. Children."

"Sooner no kids at all than to breed at your behest."

"You have long lost contact with MinaAndry."

"You could say that." When the month-long tour of the Shelf Philosophers was concluded, she had gone home with them, leaping seventeen months to continue her interrupted life on Foro. Since then, the accelerated time of the Shelf had whisked her away from him forever. "After what, three hundred and forty years up there? she's dust, her descendants won't remember her, even the language she spoke will be half-forgotten. The dead get deader, you know, as every trace of their existence is expunged. That's one thing life on Old Earth has taught us. What do you want, anyway?"

"Your research into the Formidable Caress."

"If you can call it research."

"Your work is good, from what we have seen of that portion you have shared with other scholars. You cannot help but do good work, Telni. The curiosity I saw burning in that ten-year-old boy, long ago, is still bright."

"Don't try to a.n.a.lyze me, you thing." thing."

"Tell me what you have discovered..."

After his discovery of the huge rate at which the inhabitants of Old Earth were plummeting into the future, Telni had become interested in spans of history. On the Shelf, written records went back some four thousand years of local time. These records had been compiled by a new civilization rising from the rubble of an older culture, itself wrecked by a disaster known as the Formidable Caress, thought to have occurred some six thousand years before that that.

"But in the external universe," Telni said, "ten thousand Shelf years corresponds to over three billion billion years. So much I deduced from my pendulums, swinging away amid streams of spindling s.h.i.t and cargo jockey p.i.s.s ... Everybody has always thought that the Caresses come about from local events. Something to do with the planet itself. But three billion years is long enough for events to unfold on a wider scale. Time enough, according to what Shelf scholars have reconstructed, for stars to be born and to die, for whole galaxies to swim and jostle ... I wondered if the Caresses could have some cosmic cause." years. So much I deduced from my pendulums, swinging away amid streams of spindling s.h.i.t and cargo jockey p.i.s.s ... Everybody has always thought that the Caresses come about from local events. Something to do with the planet itself. But three billion years is long enough for events to unfold on a wider scale. Time enough, according to what Shelf scholars have reconstructed, for stars to be born and to die, for whole galaxies to swim and jostle ... I wondered if the Caresses could have some cosmic cause."

"So you started to correspond with scholars on the Shelf."

"Yes. After that first visit by Mina's party, we kept up a regular link, with visits from them once every couple of years for us, once a generation for them..." It had helped that six hundred years after the shock of the War of the Cities, the Shelf cities had not indulged in another bout of warfare on any significant scale. "I spoke to the astronomers over there, about what they saw in the sky. And their archaeologists, for what had been seen in the past. There was always sn.o.bbishness, you know. Those of us down in the red think we are better because we are closer to the original stock of Old Earth; those up in the blue believe they are superior products of evolution. None of that bothered me. me. And as their generations ticked by, I think I helped shape whole agendas of academic research by my sheer persistence." And as their generations ticked by, I think I helped shape whole agendas of academic research by my sheer persistence."

"It must have been a rewarding time for you."

"Academically, yeah. I've never had any problem, academically. It's the rest of my life that's a piece of s.h.i.t."

"Tell us what you discovered."

"I don't have my notes, my books "

"Just tell us."

He sat up and stared into the face of the eerily unchanged boy who, to his credit, did not flinch. "The first Caress destroyed almost everything of what went before, on the Shelf and presumably elsewhere. Almost, but not all. Some trace inscriptions, particularly carvings on stone, have survived. Images, fragmentary, and bits of text. Records of something in the sky."