he had ever lived here, for many miles away a solitary white ruin jutted above the forest roof like a broken fang. Elsewhere, the jungle had returned to its own.
The sun was sinking below the western walls of Lys. For a breathless moment, the distant mountains seemed to burn with golden flames; then the land they guarded was swiftly drowned with shadow and the night had come.
"We should have done this before," said Hilvar, practical as ever, as he started to unload their equipment. "It'll be pitch dark in five minutes-and cold, too."
Curious pieces of apparatus began to cover the grass. A slim tripod extended a vertical rod carrying a pear-shaped bulge at its upper end. Hilvar raised this until the pear was just clear of their heads, and gave some mental signal which Alvin could not intercept. At once their little encampment was flooded with light, and the darkness retreated. The pear gave not only light but also heat, for Alvin could feel a gentle, caressing glow that seemed to sink into his very bones.
Carrying the tripod in one hand and his pack in the other, Hilvar walked down the slope while Alvin hurried behind, doing his best to keep in the circle of light. He finally pitched camp in a small depression a few hundred yards below the crest of the hill, and started to put the rest of his equipment into operation.
First came a large hemisphere of some rigid and almost invisible material which englobed them completely and protected them from the cool breeze which had now begun to blow up the face of the hill. The dome appeared to be generated by a small rectangular box which Hilvar placed on the ground and then ignored completely, even to the extent of burying it beneath the rest of his paraphernalia. Perhaps this also projected the comfortable, semitransparent couches on which Alvin was so glad to relax. It was the first time he had seen furniture materialized in Lys, where it seemed to him that the houses were terribly cluttered up with permanent artifacts which would be much better kept safely out of the way in Memory Banks.
The meal which Hilvar produced from yet another of his receptacles was also the first purely synthetic one that Alvin had eaten since reaching Lys. There was a steady blast of air, sucked through some orifice in the dome overhead, as the matter-converter seized its raw material and performed its everyday miracle. On the whole, Alvin was much happier with purely synthetic food. The way in which the other kind was prepared struck him as being appallingly unhygienic, and at least with the matter-converters you knew exactly what you were eating.
They settled down for their evening meal as the night deepened around them and the stars came out. When they had finished, it was completely dark beyond their circle of light, and at the edge of that circle Alvin could see dim shapes moving as the creatures of the forest crept out of their hiding places. From time to time he caught the glint of reflected light as pale eyes stared back at him, but whatever beasts were watching out there would come no closer, so he could see nothing more of them.
It was very peaceful, and Alvin felt utterly content. For a while they lay on their couches and talked about the things that they had seen, the mystery that enmeshed them both, and the many ways in which their two cultures differed. Hilvar was fascinated by the miracle of the Eternity Circuits which had put Diaspar beyond the reach of time, and Alvin found some of his questions very hard to answer.
"What I don't understand," said Hilvar, "is how the designers of Diaspar made certain that nothing would ever go wrong:, with the memory circuits. You tell me that the information defining the city, and all the people who live in it, is stored as patterns of electric charge inside crystals. Well, crystals will last forever-but what about all the circuits associated with them? Aren't there ever any failures of any kind?"
"I asked Khedron that same question, and he told me that the Memory Banks are virtually triplicated. Any one of the, three banks can maintain the city, and if anything goes wrong with one of them, the other two automatically correct it. Only if the same failure occurred simultaneously in two of the banks would any permanent damage be done and the chances of that are infinitesimal."
"And how