The City and the Stars Page 0,55

at last-captured and destroyed by the patient tendrils of the ivy, the generations of blindly burrowing worms, and the slowly rising waters of the lake.

Overawed by its majesty, Alvin and Hilvar walked in silence toward the colossal wreck. They passed into the shadow of a broken wall, and entered a canyon where the mountains of stone had split asunder. Before them lay the lake, and presently they stood with the dark water lapping at their feet. Tiny waves, no more than a few inches high, broke endlessly upon the narrow shore.

Hilvar was the first to speak, and his voice held a hint of uncertainty which made Alvin glance at him in sudden surprise. "There's something here I don't understand," he said slowly. "There's no wind, so what causes these ripples? The watershould be perfectly still."

Before Alvin could think of any reply, Hilvar dropped tothe ground, turned his head on one side and immersed his right ear in the water. Alvin wondered what he hoped to discover in such a ludicrous position; then he realized that he was listening. With some repugnance-for the rayless waters looked singularly uninviting-he followed Hilvar's example.

The first shock of coldness lasted only for a second; when it passsed he could hear, faint but distinct, a steady, rhythmic throbbing. It was as if he could hear, from far down in the depths of the lake, the beating of a giant heart.

They shook the water from their hair and stared at each other with silent surmise. Neither liked to say what he thought that the lake was alive.

"It would be best," said Hilvar presently, "if we searched among these ruins and kept away from the lake."

"Do you think there's something down there?" asked Alvin, pointing to the enigmatic ripples that were still breaking against his feet. "Could it be dangerous?"

"Nothing that possesses a mind is dangerous," Hilvar replied. (Is that true? thought Alvin. What of the Invaders?) "I can detect no thoughts of any kind here, but I do not believe we are alone. It is very strange."

They walked slowly back toward the ruins of the fortress, each carrying in his mind the sound of that steady, muffled pulsing. It seemed to Alvin that mystery was piling upon mystery, and that for all his efforts he was getting further and further from any understanding of the truths he sought.

It did not seem that the ruins could teach them anything, but they searched carefully among the piles of rubble and the great mounds of stone. Here perhaps, lay the graves of buried machines-the machines that had done their work se long ago. They would be useless now, thought Alvin, if the Invaders returned. Why had they never come back? But that. was yet another mystery: he had enough enigmas to deal with -there was no need to seek for any more.

A few yards from the lake they found a small clearing among the rubble. It had been covered with weeds, but they were now blackened and charred by tremendous heat, so that they crumbled to ashes as Alvin and Hilvar approached, smearing their legs with streaks of charcoal. At the center of the clearing stood a metal tripod, firmly anchored to the ground, and supporting a circular ring which was tilted on its axis so that it pointed to a spot halfway up the sky. At first sight it seemed that the ring enclosed nothing; then, as Alvin looked more carefully, he saw that it was filled with a faint haze that tormented the eye by lurking at the edge of the visible spectrum. It was the glow of power, and from this mechanism he did not doubt, had come the explosion of light that had lured them to Shalmirane.

They did not venture any closer, but stood looking at the machine from a safe distance. They were on the right track, thought Alvin; now it only remained to discover who, or what, had set this apparatus here, and what their purpose might be. That tilted ring-it was clearly aimed out into space. Had the flash they had observed been some kind of signal? That was a thought which had breath-taking implications.

"Alvin," said Hilvar suddenly, his voice quiet but urgent, "we have visitors."

Alvin spun on his heels and found himself staring at a triangle of lidless eyes. That, at least, was his first impression; then behind the staring eyes he saw the outlines of a small but complex machine. It was hanging in the air a few feet above the