“Oh, what the hell, let’s live a little, shall we? I’ll take the chocolate.”

The boy grinned. “Me, too.”

Ozzie settled on one of the rounded ebony and maroon polyp protrusions they used as chairs. He winced as he straightened his leg.

“How’s the knee?” Orion asked.

“Better. I need to do some exercises, loosen it up. It’s stiff after yesterday.” They’d walked all the way to the tip of the reef, where the trees ended abruptly and the bare oyster-gray polyp tapered away into a single long spire. They’d edged out cautiously onto the long triangular segment, feeling uncomfortably exposed. Gravity reduced proportionally the farther they went. Ozzie estimated it would finish altogether about five hundred meters past the end of the forest. They turned around and scooted back to the enclosure of the trees.

The spire was a landing point, Ozzie decided, the aerial equivalent of a jetty. Should any of the flying Silfen choose to visit, they would simply glide down onto the far end of the spire and walk in long bounds toward the main part of the reef, their weight increasing as they went.

Other than that, gravity on Island Two was constant. On the third day after the Pathfinder had reached the reef they’d traveled to the other side, which was a simple duplicate of theirs. The rim of the reef was a narrow curving cliff covered in small bushes and clumps of tall bamboolike grasses. Gravity warped alarmingly as they started to traverse the cliff, making it seem as if they were vertical during the whole transition.

Halfway around, Ozzie had looked back to see he was now standing at right angles to where he’d been a hundred meters before. Coming to terms with that was even more disconcerting than orienting himself in freefall.

While Orion dropped the chocolate cubes into their mugs, Ozzie started peeling one of the big bluish gray fruits they’d picked from the jungle. The pulp inside had a coarse texture, tasting like a cinnamon-flavored apple. It was one of eight edible fruits they’d discovered so far. Just like every other environment the Silfen paths led to, the reef was quite capable of supporting life.

Tochee emerged from the jungle, its manipulator flesh coiled around various containers it had filled with water. A small stream ran across the rumpled polyp ground fifty meters from their shelter, its water so clean they barely needed to use the filter.

“Good morning to you, friend Ozzie,” it said through the handheld array.

“Morning.” Ozzie took a drink of the chocolate.

“I have detected no electrical power circuit activity with my equipment.” The big alien held up a couple of sensors it had brought with it. “The machinery must be very deep inside the reef.”

“Yeah, you’re probably right.” Even after all this time spent together, Tochee hadn’t quite grasped the fact that Ozzie liked a bit of peace and quiet at breakfast.

“Where did you go?” Orion asked as Ozzie munched stoically on his fruit.

“Five kilometers in that direction.” Tochee formed a tentacle out of its manipulator flesh, and pointed.

“I think the middle is that way.” Orion pointed almost at right angles to Tochee’s tentacle.

“Are you sure?”

“I dunno. Where is it, Ozzie?”

Ozzie jerked a thumb over his shoulder. “There, nine kilometers.”

“I apologize,” Tochee said. “My instruments do not possess a navigation function like yours.”

“Did you see anything interesting?” Orion asked.

“Many trees. Some small flying creatures. No large or sentient life.”

“Too bad.” The boy cut a big slice out of a purplish fruit with his penknife, and bit into it eagerly. Juice dribbled down his chin, getting caught in his wispy beard. “Were there any caves?”

“I did not see any.”

“There’s got to be a way in to the core somewhere. I wonder if it’s right on the tip of the spires. There can’t be any gravity along the axis, that’s where it all balances out, Ozzie said so. I bet that’s just one long tunnel the whole length of this thing.”

“Logic would dictate the shortest distance. An access passage to the core would surely begin on the surface at the middle.”

“Yeah. I bet there’s a whole load of caves and stuff. It’ll be where the reef’s inhabitants live, like the Morlocks.”

Ozzie took another drink of chocolate, not making eye contact. He was already regretting telling that story.

“Do you still think something lives here, friend Orion?” Tochee asked.

“What’s the point of it otherwise?”

“I have seen no sign of any large creature.”

“No, ‘cause they’re underground.”

Ozzie finished his chocolate and retied his hair with a small band of leather so that it didn’t flop down over his eyes. “They are not underground,” he said. “You do not build islands in something like the gas halo, and then populate them with troglodyte species. Nothing lives here.”

“What’s a trogodite?” Orion asked.

“Someone who lives underground.”

“Excuse me, friend Ozzie,” Tochee said. “But this whole gas halo is lacking in logic. We might yet find some life belowground. Why else would you build islands in the sky?”

“Carbon sinks,” Ozzie said. “It’s all a question of scale, which is admittedly difficult to get your head around. Even I’m having serious trouble with this when I look up and see sky that goes on forever. But we know that there is a lot of animal life flapping around inside the gas halo. As it’s a standard oxygen-nitrogen mix it’s pretty safe to say they all breathe oxygen, and exhale carbon dioxide, or some other waste product. Now I’m sure it would take billions of years for all those animals to poison something as gigantic as the gas halo, but it will happen unless the opposite process is active. You can either do it artificially, with machines; or the green way, with plants. And that’s what this reef is, a part of the ecosystem. It probably doubles as a food garden and watering hole as well. The air-desert equivalent of an oasis.”

“You said there was machinery inside it,” Orion said, his tone accusing.

“There is some kind of gravity generator, certainly, man, and that probably has a steering function; I’m pretty sure it was put on a collision course with us. The rest of it is all biological.”

“What’s the point if they can clean the air with machines?”

“I suspect they built all of this just for the hell of it, man, the enjoyment of living in something so utterly fantastic. I know I would if I could. I already did something like this on a minuscule scale back home.”

“Did you?”

“Very small scale, yeah.”

“What?”

“It’s an artificial environment; nothing special, not important. Look, the reason I’m interested in trying to locate the gravity generator in this reef is because I might figure out how to use it to steer us somewhere.” He held a hand up to stall both of them. “And no, guys, I don’t know where yet, but a degree of control would be useful at this moment in time, okay? We really are out of all other options.”

“You said that back on the water island.” Orion’s grin was pure disrespect.

“Shows you how little I know. Come on, Tochee’s probably right about the inspection hatch being close to the center. Let’s go see if we can find it.”

The intricacy of the reef’s jungle fascinated Ozzie; it was a work of art. There was a near-uniform gap between the ground and the first level of branches of about four meters. Just right for a human or a Silfen to walk comfortably in the low gravity without hitting their head on branches. In fact, if you happened to push off too hard the lacework of branches and twigs was dense enough for a simple slap of the hand to help flatten out the arc of your glide-walk. An overhead safety net, basically. Ozzie was convinced that was deliberate. So if the trees weren’t pruned, and he’d seen nothing to indicate they were, they must have been configured at a genetic level to grow like that. Even for a society with the resources to build the gas halo, that was a lot of work.