His tribe followed him. Dik and Tet, of course, because they were boys and Burl led on to high adventures in which so far nobody had been killed. Dor followed because--he being the strongest man in the tribe--he had thoughtfully realized that his strength was not as useful as Burl's brains and other qualities. Cori followed because she had children, and they were safer where Burl led than anywhere else. The others followed to avoid being left alone. The procession toiled on and up. Presently Burl noticed that the air seemed clearer, here. It was not the misty, only half transparent stuff of the valley. He could see for miles to right and left. He realized the curvature of the mountain-face. But he could not see the valley. The mist hid that. Suddenly he realized that he saw the cloud-bank overhead as an object. He had never thought of it specifically before. To him it had been simply the sky. Now he saw an indefinite lower surface which yet definitely hid the heights toward which he moved. He and his followers were less than a thousand feet below it. It appeared to Burl that presently he would run into an obstacle which would simply keep him from going any further. The idea was disheartening. But until it happened he obstinately climbed on. He observed that the thing which was the sky did not stay still. It moved, though slowly. A little higher, he could see that there were parts of it which were actually lower than he was. They moved also, but they moved away from him as often as they moved toward him. He had no experience of any dangerous thing which did not leap at its victims. Therefore he was not afraid. In fact, presently he noticed that the whiteness which was the cloud-layer seemed to retreat before him. He was pleased. Weak things like humans fled from enemies. Here was something which fled at his approach! His followers undoubtedly saw the same thing. Burl had killed spiders. He was a remarkable person. This unknown white stuff was afraid of him. Therefore it was wise to stay close to Burl. Burl found his vanity inflamed by the fact that always--even at its thickest--the white cloud-stuff never came nearer than some dozens of feet. He swaggered as he led his people up. And presently there was brightness about them. It was a greater brightness than the tribesfolk had ever known. They knew daylight as a grayness in which one could see. Here was a brightness that shone. They were not accustomed to brightness. They were not accustomed to silence, either. The noises of the valley were like all the noises of the lowlands. They had been in the ears of every one of the human beings since they could hear at all. They had gradually diminished as the valley dropped behind them. Now, in the radiant white mist which was the cloud-layer, there were no sounds at all, and the fact was suddenly startling.