“Not one person in a thousand would ever notice that unless they were looking for it,” said Rorden, “and even then, it would mean nothing to them. At first I felt rather foolish myself, standing on that slab and going through different combinations of control thoughts. Luckily the circuits must be fairly tolerant, and the code thought turned out to be ‘Alaine of Lyndar.’ I tried TTarlan Zey’ at first, but it wouldn’t work, as I might have guessed. Too many people would have operated the machine by accident if that trigger thought had been used.”
“It sounds very simple,” admitted Alvin, “but I don’t think I would have found it in a thousand years. Is that how the Associators work?”
Rorden laughed. “Perhaps,” he said. “I sometimes reach the answer before they do, but they always reach it.” He paused for a moment. “We’ll have to leave the shaft open: no one is likely to fall down it.”
As they sank smoothly into the earth, the rectangle of sky dwindled until it seemed very small and far away. The shaft was lit by a phosphorescence that was part of the walls, and seemed to be at least a thousand feet deep. The walls were perfectly smooth and gave no indication of the machinery that had lowered them.
The doorway at the bottom of the shaft opened automatically as they stepped towards it. A few paces took them through the short corridor-and then they were standing, overawed by its immensity, in a great circular cavern whose walls came together in a graceful, sweeping curve three hundred feet above their heads. The column against which they were standing seemed too slender to support the hundreds of feet of rock above it. Then Alvin noticed that it did not seem an integral part of the chamber at all, but was clearly of much later construction. Rorden had come to the same conclusion.
“This column,” he said, “was built simply to house the shaft down which we came. We were right about the moving ways-they all lead into this place.”
Alvin had noticed, without realizing what they were, the great tunnels that pierced the circumference of the chamber. He could see that they sloped gently upwards, and now he recognized the familiar grey surface of the moving ways. Here, far beneath the heart of the city, converged the wonderful transport system that carried all the traffic of Diaspar. But these were only the severed stumps of the great roadways: the strange material that gave them life was now frozen into immobility.
Alvin began to walk towards the nearest of the tunnels. He had gone only a few paces when he realized that something was happening to the ground beneath his feet. It was becoming transparent. A few more yards, and he seemed to be standing in mid-air without any visible support. He stopped and stared down into the void beneath.
“Rorden!” he called. “Come and look at this!”
The other joined him, and together they gazed at the marvel beneath their feet. Faintly visible, at an indefinite depth, lay an enormous map-a great network of lines converging towards a spot beneath the central shaft. At first it seemed a confused maze, but after a while Alvin was able to grasp its main outlines. As usual, he had scarcely begun his own analysis before Rorden had finished his.