 Why does Loy Chuk build an artificial environment for Ned?
THE ETERNAL WALL By RAYMOND Z. GALLUN A scream of brakes, the splash into icy waters, a long descent into alkaline depths ... His old car rattled and roared as he swung it recklessly around Pit Bend. Another car leaped suddenly into view, its lights glaring blindingly past a high, up-jutting mass of Jurassic rock at the turn of the road. Dazzled, and befuddled by his own rash speed, Ned Vince had only swift young reflexes to rely on to avoid a fearful, telescoping collision. An incredible science, millions of years old, lay in the minds of these creatures. His car hit the white-painted wooden rail sideways, crashed through, tumbled down a steep slope, struck a huge boulder, bounced up a little, and arced outward, falling as gracefully as a swan-diver toward the inky waters of the Pit, fifty feet beneath.... Ned Vince was still dimly conscious when that black, quiet pool geysered around him in a mighty splash. Movement was slower now, as he began to sink, trapped inside his wrecked car. Nothing that he could imagine could mean doom more certainly than this. The Pit was a tremendously deep pocket in the ground, spring-fed. The edges of that almost bottomless pool were caked with a rim of white—for the water, on which dead birds so often floated, was surcharged with alkali. The welt, left by the blow he had received on his forehead, put a thickening mist over his brain, so that he could not think clearly. Presently, when he could no longer hold his breath, bitter liquid was sucked into his lungs. The ripples that had ruffled the surface waters in the Pit, quieted again to glassy smoothness. Time, the Brother of Death, and the Father of Change, seemed to wait.... Kaalleee!..." Tik, tik, tik!..." Lacking qualities identifiable as human, the disturbance was still like the babble of a group of workmen who have discovered something remarkable. The icy breeze tore tiny puffs of dust from grotesque, angling drifts of soil, nearly waterless for eons. Patches of drab lichen grew here and there on the up-jutting rocks, but in the desert itself, no other life was visible. A launching catapult for the last space ships built by the gods in exodus, perhaps it was—half a million years ago. Glacial ages, war, decadence, disease, and a final scattering of those ultimate superhumans to newer worlds in other solar systems, had done that. Tik, tik, tik!..."
 He needs a habitat for Ned, so he can study Ned in a natural setting.
 He needs to keep Ned calm. If Ned believes himself to back in his own time, he will remain calm.  He realizes Ned is mentally unstable from the trauma of being brought back to life. He doesn't want Ned to commit suicide.  He needs a habitat for Ned until they can figure out time travel.  He needs a habitat for Ned, so he can study Ned in a natural setting.