Rolling bass wrenchings strummed through the walls and floor. Her heart thudded painfully and wind whistled in her ears.

             The strain of withstanding the steadily rising acceleration warped the vines. They stretched and twisted but held the long, tubular trees tight to the underside. She saw that the nub was festooned with shrubs and brush. The Pinwheel stretched away into blue-black vistas as the air thinned around them. The wind in their compartment wailed and she sucked in air, fearing that there was a leak.

             But Seeker patted her outstretched hand and she glanced at the great beast. Its eyes were closed as though asleep. This startled her and a long moment passed before she guessed that Seeker could have done this before, that this was not some colossal accident they had blundered into. As if in reply Seeker licked its lips, exposing black gums and pointed yellow teeth.

             Her ears popped. She looked outward again, through the slow buffeting of tree trunks. "Upward" was now tilted away from the darkening bowl of sky, but still along the chestnut-brown length of the Pinwheel, as they rotated with it. Black shrubs dotted the great expanse that dwindled away, gray laminations making the perspective even starker. Cross-struts of cedar-red tied the long strips into an interlocking network that twisted visibly in the howling gale that tore along it.

             Once they smacked into the nearest tree and a branch almost punched through the window, but their tree wrenched aside and the impact slammed against the wall.

             Her ears popped again and her breath came raggedly. Along the great strips of lighter wood, walnut-colored edges rose. They canted, sculpting the wind—and the roaring gale subsided, the twisting and wrenching lessened. Pops and creaks still rang out but she felt a subtle loosening in the coupled structure.

             The last thin haze of atmosphere faded into star-sprinkled black. She felt that an invisible, implacable enemy sat on her chest and would forever, talking to her in a language of wrenching low bass notes. Cold, thin air stung her nostrils but there was enough if she labored to fill her lungs.

             The ample curve of the planet rose serenely at the base of the window as she panted. Its smooth ivory cloud decks seemed near enough to touch . . . but she could not raise her arms.

             Along the tapering length of the Pinwheel, slow, lazy undulations were marching. They came toward her, growing in height. When the first arrived it gave the nub a hard snap and the trees thrashed on their vine-teathers. The turbulence which the entire Pinwheel felt had summed into these waves, which dissipated in the whip-crack at its ends. Tree trunks thumped and battered but their pressure held.

             Seeker licked its lips again without opening its eyes.

             They revolved higher. She could see the complete expanse of the Pinwheel. It curved slightly, tapering away, like an infinite highway unconcerned with the impossibility of surmounting the will of planets. Vines wrapped along it and near the middle a green forest flourished.

             The far end was a needle-thin line. As she watched, its point plunged into the atmosphere. Undulations from this shock raced back toward her. When these reached her the buffetings were mild, for the trees were now tied snugly against the underside of the Pinwheel's nub end.

             Deep, solemn notes beat through the walls. The entire Pinwheel was like a huge instrument strummed by wind and gravity, the waves singing a strange song that sounded through her bones.

             The Pinwheel was now framed against the whole expanse of Earth. Cley still felt strong acceleration into the compartment's floor, but it was lesser now as gravity countered the centrifugal whirl. Their air, too, thickened as the tree's walls exuded a sweet-scented, moist vapor.

             The spectacle of her world, spread out in silent majesty, struck her. They were nearing the top of their ascent, the Pinwheel pointing vertically, as if to bury itself in the heart of the planet.

             The Pinwheel throbbed. She had felt its many adjustments and percussive changes as it struggled against both elements, air and vacuum. Only a short while ago she had thought that the ravenous green, eating at the pale deserts, waged an epic struggle. Now she witnessed an unending whirl of immeasurably greater difficulty.

             And in a glance she knew that the Earth itself and the Pinwheel were two similar systems, brothers of vastly different scales.

             The Pinwheel was like a tree, quite certainly alive and yet 99 percent dead. Trees were spires of dead wood, cellulose used by the ancestors of the living cells that made its bark.

             Earth, too, was a thin skin of verdant life atop a huge bulk of rocks. But far down in the magma were elements of the ancestral hordes which had come before. The slide and smack of whole continents rode on a slippery base of limestone, layers built up from an infinitude of seashell carcasses. All living systems, in the large, were a skin wrapped around the dead.

             "Good-bye," Seeker said, getting up awkwardly. Even its strength was barely equal to the centrifugal thrust.

             "What! You're not leaving?"

             "We both are."

             A loud bang. Cley felt herself falling. She kicked out in her fright and only managed to propel herself into the ceiling. She struck on her neck wrong and painfully rebounded. Her mind kept telling herself she was falling, despite the evidence of her eyes—and then some ancient subsystem of her mind cut in, and she automatically quieted.

             She was not truly falling, except in a sense used by physicists. She was merely weightless, bouncing about the compartment before Seeker's amused yawn.

             "We're free!"

             "For a bit."

             "What?"

             "See ahead."

             Their vines had slipped off. Freed, their tree shot away from the Pinwheel. They went out on a tangent to its great circle of revolution. Already the nub was a shrinking spot on the huge, curved tree that hung between air and space. She had an impression of the Pinwheel dipping its mouth into the rich swamp of Earth's air, drinking its fill alternately from one side of itself and then the other.

             But what kept it going, against the constant drag of those fierce winds? She was sure it had some enormous skill to solve that problem, but there was no sign what that might be.

             She looked out, along the curve of Earth. Ahead was a dark-brown splotch on the star-littered blackness.

             "A friend," Seeker said. "There."

27

             They rose with surprising speed. The Pinwheel whirled away, its grandiose gyre casting long shadows along its woody length.

             Despite the winds it suffered, bushes clung to its flanks. The upper end, which they had just left, now rotated down toward the coming twilight. Its midpoint was thickest and oval, following a circular orbit a third of Earth's radius above the surface. At its furthest extension, groaning and popping with the strain, the great log had reached a distance two-thirds of the Earth's radius out into the cold of space.

             They had been flung off at better than thirteen kilometers per second. This was enough to take the trees to other planets, though that was not their destination. They shot ahead of the nub, watching it turn downward with stately resolution, as though gravely bowing to necessity by returning to the planet which held it in bondage.