The boy Farr was crouched against a section of bark a mansheight or so from everyone else. He looked as if he were suffering a bit: visibly shivering, his chest rising and falling rapidly in the attenuated Air, his hands pushing leaves into his downturned mouth with an urgency that looked more like a craving for comfort than for food.

Adda, with a single flip of his legs, Waved briskly over to the boy; he leaned toward Farr and winked with his good eye. “How are you doing?”

The boy looked up at him, lethargic despite the shivering, and his voice, when he spoke, was deepened by the cold. “I can’t seem to get warm.”

Adda sniffed. “That’s the way it is, up here. The Air’s too thin for us, see. And if you go higher, toward the Crust, it gets thinner still. But there’s no need to be cold.”

Farr frowned. “What do you mean?”

For answer Adda grinned. He raised his spear of hardened wood and aligned it parallel to the tree trunk, along the direction of the Magfield flux lines. He hefted it for a few seconds, feeling its springy tension. Then he said, “Watch and remember.”

The boy, eyeing the quivering spear with wide eyes, scrambled back out of the way.

Adda braced himself against the Magfield. With a single movement — he remained lithe in spite of everything, Adda congratulated himself — Adda thrust the spearpoint deep into the bulk of the tree. The first stab took the spearpoint through the bark and perhaps a hand’s length into the wood. By working the haft of the spear, twisting it in his hands, Adda was able to drive the spear further into the flesh of the branch, to perhaps half an arm’s length.

That done, feeling his chest drag at the thin Air, Adda turned to make sure Farr was still watching. “Now,” he rasped. “Now comes the magic.”

He twisted in the Air and placed his feet against the branch, close to the line of his half-buried spear. Then he bent and wrapped both hands around the protruding shaft of the spear, squatted so that his legs were bent and his back was straight, and heaved upward, using the spear as a lever to prize open the wood of the branch.

…Actually it was a long time since he’d done this, he realized a few heartbeats after starting. His palms grew slick with superfluid sweat, a steady ache spread along his back, and for some reason the vision of his good eye was starting to tremble and blur. And, though the spear bowed upward a bit as he strained, the branch did little more than groan coldly.

He let go of the spear and wiped his palms against his thighs, feeling the breath rattle in his chest. He carefully avoided eye contact with the boy.

Then he bent to the spear again.

This time, at last, the branch gave way; a plate of it the size of his chest yielded and lifted up like a lid. Adda felt his aching legs spring straight, and he tumbled away from the branch. Quickly recovering his dignity, he twisted in the Air, ignoring the protests from his back and legs, and Waved back to Farr and the opened branch. He looked down at his handiwork appraisingly and nodded. “Not as difficult as it looks,” he growled at the boy. “Used to do that one-handed… But trees have got tougher since I was your age. Maybe something to do with this damn spin weather.”

But Farr wasn’t listening; he crept forward to the wound in the branch and stared into it with fascination. Close to the rim of the ripped bark the wood was a pale yellow, the material looking much like that of the spear Adda had used. But further in, deeper than a hand’s length, the wood was glowing green and emitting a warmth which — even from half a mansheight away — Adda could feel as a comforting, tangible presence against his chest. The glow of the wood sparkled against Farr’s face and evoked verdant shadows within his round eyes.

Dura, Logue’s ungainly daughter, joined them now; she shot a brief smile of thanks to Adda as she crouched beside her brother and raised her palms to the warmth of the wood. The green fire scattered highlights from her limbs and face which made her look, Adda thought charitably, half-attractive for once. As long as she didn’t move about too much and reveal her total lack of grace, anyway.

Dura said to Farr, “Another lesson. What’s making the wood burn?”

He smiled at her, eyecups full of wood-glow. “Heavy stuff from the Crust?”

“Yes.” She leaned toward Farr so that the heads of brother and sister were side by side over the glowing wood, their faces shining like two leaves. Dura went on, “Proton-rich nuclei on their way to the leaves. The tree branch is like a casing, you see, enclosing a tube where the pressure is lower than the Air. But when the casing is breached the heavy nuclei inside fission, decaying rapidly. What you’re seeing is nuclei burning into the Air…”

Adda saw how Farr’s smooth young face creased with concentration as he absorbed this new bit of useless knowledge.

Useless?

Well, maybe, he thought; but these precious, abstract facts, polished by retelling and handed down from the earliest days of the Human Beings — from the time of their expulsion from Parz City, ten generations ago — were treasures. Part of what made them human.

So Adda nodded approvingly at Dura and her attempts to educate her brother. The Human Beings had been thrust into this upflux wilderness against their will. But they were not savages, or animals; they had remained civilized people. Why, some of them could even read; a handful of books scraped painfully onto scrolls of pigskin with styli of wood were among the Human Beings’ principal treasures…

He leaned toward Dura and said quietly, “You’ll have to go on, you know. Deeper into the forest, toward the Crust.”

Dura started. She pulled away from the trunk-wound, the light of the burning nuclei shining from the long muscles of her neck. The other Human Beings, a few mansheights away, were still clustered about the treetops; most of them, having crammed their bellies full, were gathering armfuls of the succulent leaves. She said, “I know. But most of them want to go back to the camp already, with their leaves.”

Adda sniffed. “Then they’re damn fools, and it’s a shame the spin weather didn’t take them instead of a few with more sense. Leaves taste good but they don’t fill a belly.”

“No. I know.” She sighed and rubbed the bridge of her nose, ran a finger around the rim of one eyecup absently. “And we have to replace the Air-pigs we lost in the spin storm.”

“Which means going on,” Adda said.

She said with a weary irritation, “You don’t need to tell me, Adda.”

“You’ll have to lead them. They won’t go by themselves; folk aren’t like that. They’re like Air-pigs: all wanting to follow the leader but none wanting to lead.”

“They won’t follow me. I’m not my father.”

Adda shrugged. “They won’t follow anyone else.” He studied her square face, seeing the doubts and submerged strength in its thin lines. “I don’t think you really have a choice.”

“No,” she sighed, straightening up. “I know.” She went to talk to the tribesfolk.

When she returned to the nuclear fire, only Philas, the widow of Esk, came with her. The two women Waved side by side. Dura’s face was averted, apparently riven with embarrassment; Philas’s expression was empty.

Adda wasn’t really surprised at the reaction of the rest. Even when it was against their own damn interest, they’d snub Logue’s daughter.

He was interested to see Philas with Dura, though. Everyone had known about Dura’s relationship with Esk; it was hardly the sort of thing that could be kept quiet in a community reduced to fifty people, counting the kids.

It had been against the rules. Sort of. But it was tolerated, and hardly unique — as long as Dura obeyed a few unspoken conventions. Such as restricting her reaction to Esk’s death, keeping herself away from the widowed Philas.

Just another bit of stupidity, Adda thought. The Human Beings had once numbered hundreds — even in the days of Adda’s grandfather there had been over a hundred adults — and maybe then conventions about adultery might have made sense. But not now.