solar heat seeped through the hull of Rama. And when ice turns into water, it occupies less volume.
So the sea had been sinking below the upper layer of ice, leaving it unsupported. Day by day the strain had been building up; now the bank of ice that encircled the equator of Rama was collapsing, like a bridge that had lost its central pier. It was splintering into hundreds of floating islands, which would crash and jostle into each other until they, too, melted. Norton’s blood ran suddenly cold when he remembered the plans that were being made to reach New York by sledge.
The tumult was swiftly subsiding; a temporary stalemate had been reached in the war between ice and water. In a few hours, as the temperature continued to rise, the water would win, and the last vestiges of ice would disappear. But in the long run ice would be the victor, as Rama rounded the Sun and set forth once more into the interstellar night.
Norton remembered to start breathing again; then he called the party nearest the sea. To his relief, Rodrigo answered at once. No, the water hadn’t reached them. No tidal wave had come sloshing over the edge of the cliff. “So now we know,” he added calmly, “why there is a cliff.” Norton agreed silently. But that hardly explains, he thought, why the cliff on the southern shore is ten times higher.
The hub searchlight continued to scan around the world. The awakened sea was steadily calming, and the boiling white foam no longer raced outward from capsizing ice floes. In fifteen minutes, the main disturbance was over.
But Rama was no longer silent. It had awakened from its sleep, and ever and again there came the sound of grinding ice as one berg collided with another.
Spring had been a little late, Norton told himself, but winter had ended.
And there was that breeze again, stronger than ever. Rama had given him enough warnings; it was time to go. As he neared the halfway mark, Norton once again felt gratitude for the darkness that concealed the view above—and below. Though he knew that more than ten thousand steps still lay ahead of him, and could picture the steeply ascending curve in his mind’s eye, the fact that he could see only a small portion of it made the prospect more bearable.
This was his second ascent, and he had learned from his mistakes on the first. The great temptation was to climb too quickly in this low gravity; every step was so easy that it was hard to adopt a slow, plodding rhythm. But unless one did this, after the first few thousand steps strange aches developed in the thighs and calves. Muscles that one never knew existed started to protest, and it was necessary to take longer and longer periods of rest. Toward the end of the first climb, Norton had spent more time resting than climbing, and even then it was not enough. He had suffered painful leg cramps for the next two days, and would have been almost incapacitated had he not been back in the zero-gravity environment of the ship.
So this time he had started with almost painful slowness, moving like an old man. He had been the last to leave the plain, and the others were strung out along the half-kilometer of stairway above him. He could see their lights moving up the invisible slope ahead.
He felt sick at heart at the failure of his mission, and even now hoped that this was only a temporary retreat. When they reached the hub, they could wait until any atmospheric disturbances had ceased. Presumably there would be a dead calm there, as at the center of a cyclone, and they could wait out the expected storm in safety.
Once again he was jumping to conclusions, drawing dangerous analogies from Earth. The meteorology of a whole world, even under steady-state conditions, was a matter of enormous complexity. After several centuries of study, terrestrial weather forecasting was still not absolutely reliable. And Rama was not merely a completely novel system; it was also undergoing rapid changes, for the temperature had risen several degrees in the last few hours. Yet there was no sign of the promised hurricane, though there had been a few feeble gusts from apparently random directions.
They had now climbed five kilometers, which in this low and steadily diminishing gravity was equivalent to less than two on Earth. At the third level, three kilometers from the axis, they