The City and the Stars Page 0,93

and leaves were infested with an entire fauna of spidery animals, which must! spend their lives floating far above the surface of the globe, continuing the universal battle for existence on their lonely aerial islands. Presumably they must from time to time have some contact with the ground; Alvin saw one of the great balloons suddenly collapse and fall out of the sky, its broken, envelope acting as a crude parachute. He wondered if this was an accident, or part of the life cycle of these strange entities.

Hilvar slept while they waited for the next planet to approach. For some reason which the robot could not explain to them, the ship traveled slowly-at least by comparison with its Universe-spanning haste-now that it was within a Solar System. It took almost two hours to reach the world that Alvin had chosen for his third stop, and he was a little surprised that any mere interplanetary journey should last so long.

He woke Hilvar as they dropped down into the atmosphere.

"What do you make of that?" he asked, pointing to the vision screen.

Below them was a bleak landscape of blacks and gray, showing no sign of vegetation or any other direct evidence of life. But there was indirect evidence; the low hills an shallow valleys were dotted with perfectly formed hemispheres, some of them arranged in complex, symmetrical patterns.

They had learned caution on the last planet, and aft carefully considering all the possibilities remained high in the atmosphere while they sent the robot down to investigate. Through its eyes, they saw one of the hemispheres approach until the robot was floating only a few feet awa from the completely smooth featureless surface.

There was no sign of any entrance, nor any hint of the pur pose which the structure served. It was quite large - a hundred feet high; some of the other hemispheres we larger still. If it was a building, there appeared to be no wa in or out.

After some hesitation, Alvin ordered the robot to move forward and touch the dome. To his utter astonishment, it refused to obey him. This indeed was mutiny-or so at sight it seemed.

"Why won't you do what I tell you?" asked Alvin, wh he had recovered from his astonishment.

"It is forbidden," came the reply.

"Forbidden by whom?"

"I do not know."

"Then how-no, cancel that. Was the order built into you?"

"No."

That seemed to eliminate one possibility. The builders of these domes might well have been the race who made the robot, and might have included this taboo in the machine's original instructions.

"When did you receive the order?" asked Alvin.

"I received it when I landed."

Alvin turned to Hilvar, the light of a new hope burning in his eyes.

"There's intelligence here! Can you sense it?"

"No," Hilvar replied. "This place seems as dead to me as the first world we visited."

"I'm going outside to join the robot. Whatever spoke to it may speak to me."

Hilvar did not argue the point, though he looked none too happy. They brought the ship to earth a hundred feet away from the dome, not far from the waiting robot, and opened the air lock.

Alvin knew that the lock could not be opened unless the ship's brain had already satisfied itself that the atmosphere was breathable. For a moment he thought it had made a mistake-the air was so thin and gave such little sustenance to his lungs. Then, by inhaling deeply, he found that he could grasp enough oxygen to survive, though he felt that a few minutes here would be all that be could endure.

Panting hard, they walked up to the robot and to the curving wall of the enigmatic dome. They took one more stepthen stopped in unison as if hit by the same sudden blow. In their minds, like the tolling of a mighty gong, had boomed a single message:

DANGER. COME NO CLOSER.

That was all. It was a message not in words, but in pure thought. Alvin was certain that any creature, whatever its level of intelligence, would receive the same warning, in the same utterly unmistakable fashion-deep within its mind.

It was a warning, not a threat. Somehow they knew that it was not directed against them; it was for their own protection.

Here, it seemed to say, is something intrinsically dangerous, and we, its makers, are anxious that no one shall be hurt through blundering ignorantly into it.

Alvin and Hilvar stepped back several paces, and looked at each other, each waiting for the other to say what was in his mind.