He cupped his hands to his mouth. "You!"

Small faces turned up to him. One pilot tumbled backwards.

"Build up your bowls!" Pallis called angrily. "Get a decent amount of smoke. All you're doing with those damn blankets is blowing around two fifths of five per cent of bugger all…"

The pilots inched their way to their bowls and began feeding fresh kindling to the tiny flames.

Nead tugged at Pallis's sleeve. "Pilot. Should that be happening?"

Pallis looked. Two trees, wrapped in distorted blankets of smoke, were inclining blindly towards one another, their amateur pilots evidently absorbed in the minutiae of blankets and bowls.

"No, it bloody shouldn't be happening." Pallis spat. "Barman! Get us down there, and fast—"

The trees' first touch was almost tender: a rustle of foliage, a gentle kiss of snapping twigs. Then the first snag occurred, and the two platforms locked and shuddered. The crews of the trees gaped with sudden horror at each other.

The trees kept turning; now sections of rim were torn away and wooden shards rained through the air. A branch caught and with a scream like some animal's was torn away by the root. Now the trees began to roll into each other, in a vast, slow, noisy collision. The smooth platforms of foliage shattered. Fist-sized splinters sailed past the plate craft; Nead howled and covered his head.

Pallis glared down at the crews of the dying trees. "Get off there! The damn trees are finished. Get down your cables and save yourselves."

They stared up at him, frightened and confused. Pallis shouted on until at last he saw them slide down rippling cables to the deck.

The trees were now locked in a doomed embrace, their angular momenta mingling, their trunks orbiting in a whirl of foliage and branch stumps. Wall-sized sections of wood splintered away and the air was filled with the creak of rending timber; Pallis saw fire bowls go sailing through the air, and he prayed that the crews had had the foresight to douse their flames.

Soon little was left but the trunks, locked together by a tangle of twisted branches; now the trees' anchoring cables were torn loose like shoulders from sockets, and the freed trunks pirouetted with a strange grace, half tumbling.

At last the trunks crashed to the deck, exploding in a storm of fragments. Pallis saw men running for their lives from the rain of wood. For some minutes splinters fell, like a hail of ragged daggers; then, slowly, men began to creep back to the crash site, stepping over tree cables which lay like the limbs of a corpse among the ruins.

Silently Pallis motioned to Jame. "There's nothing we can do here; let's get on." The plate craft lifted and returned to its patrols.

For several more hours Pallis's plate skimmed about the flying forest. At the end of it Jame was muttering angrily, his face blackened by the rising smoke, and Pallis's throat was raw with shouting. At last Nead placed his sextant in his lap and sat back with a smile. "That's it," he said. "I think, anyway…"

"What's what?" Jame growled. "Is the Raft out from under the bloody star now?"

"No, not yet. But it's got enough momentum without further impulse from the trees. In a few hours it will drift to a halt far enough from the path of the star to be safe."

Pallis lay back in the netting of the plate and took a draught from a drink globe. "So we've made it."

Nead said dreamily, "It's not quite over for the Raft yet. When the star passes through the plane in which the Raft lies there will be a few interesting tidal effects."

Pallis shrugged. "Nothing the Raft hasn't endured before."

"It must be a fantastic sight, Pallis."

"Yes, it is," the pilot mused. He remembered watching cable shadows lengthen across the deck; at last the circumference of the star disc would touch the horizon, sending light flaring across the deck. And when the main disc had dropped below the Rim there would be an afterglow, what the Scientists call a corona…

Jame squinted into the sky. "How often does this happen, then? How often does the Raft get in the way of a falling star?"

Pallis shrugged. "Not often. Once or twice a generation. Often enough for us to have built up skills to deal with it."

"But you need the Scientists — the likes of this one—" Jame jerked a thumb at Nead " — to work out what to do."

"Well, of course." Nead sounded amused. "You can't do these things by sticking a wet finger into the wind."

"But a lot of the Scientists are going to bugger off, on this Bridge thing."

"That's true."

"So what's going to happen when the next star comes down? How will they move the Raft then?"

Nead sipped a drink easily. "Well, our observations show that the next star — a long way up there—" he pointed upwards " — is many thousands of shifts away from endangering the Raft."

Pallis frowned. "That doesn't answer Jame's question."

"Yes, it does." Nead's blank young face bore a look of puzzlement. "You see, by that time we don't expect the Nebula to be sustaining life anyway. So the problem's rather academic, isn't it?"

Pallis and Jame exchanged glances; then Pallis turned to the rotating forest under his craft and tried to lose himself in contemplation of its steady serenity.

Rees hardly slept during his last rest period before the Bridge's departure.

A bell tolled somewhere.

At last it was time. Rees rose from his pallet, washed quickly, and emerged from his temporary shelter, feeling only a vast relief that the time had come.

The Bridge in its box of scaffolding was the center of frantic activity. It lay at the heart of a fenced-off area two hundred yards wide which had become a miniature city; former Officers' quarters had been commandeered to give hopeful migrants temporary accommodation. Now small knots of people walked uncertainly toward the Bridge. Rees recognized representatives of all the Nebula's cultures: the Raft itself, the Belt, and even a few Bon-eys. Each refugee carried the few pounds of personal belongings allowed. A queue was forming at the open port of the Bridge, behind a human chain which passed into the interior a few final supplies, books, small environmental monitoring instruments. There was an air of purposefulness about the scene and Rees slowly began to believe that this thing was actually going to happen…

Whatever the future held he could only be glad that this period of waiting, with all its divisiveness and bitterness, was over. After the moving of the Raft, society had disintegrated rapidly. It had been a race to complete their preparations before things fell apart completely; and as time had passed — and more delays and problems had been encountered — Rees had felt the pressure build until it seemed he could hardly bear it.

The amount of personal animosity he had encountered had astonished him. He longed to explain to people that it was not he who was causing the Nebula to fail; that it was not he who decreed the physical laws which constrained the number of evacuees.

…And it had not been he — alone — who had drawn up the list.

The preparation of that list had been agonizing. The idea of a ballot had been rejected quickly; the composition of this colony could not be left to chance. But how to select humans — families, chains of descendants — for life or extinction? They had tried to be scientific, and so had applied criteria like physical fitness, intelligence, adaptabilty, breeding age… And Rees, embarrassed and disgusted by the whole process, had found himself on most of the candidate lists.

But he had stayed with it; not, he prayed, merely in order to ensure his own survival, but to do the best job he could. The selection process had left him feeling soiled and shabby, unsure even of his own motivations.

In the end a final list had emerged, an amalgam of dozens of others drawn together by Decker's harsh arbitration. Rees was on it. Roch wasn't. And so, Rees reflected with a fresh burst of self-loathing, he had finished by neatly fulfilling the worst expectations of Roch and his like.