"Yes, we'll follow him," Wessel murmured. "Just as long as he sticks fairly close to the radite veins, we will. _This_ is what I'm going by." And he touched the little metallic device at his wrist, which Jim knew was susceptible through super-sensitive coils to all radite emanations within a radius of several miles. Conley frowned but nodded mute agreement. And now for the first time it really dawned on Jim that he and Kaarji were apart from these other men. He and the Martian were up here seeking, not radite deposits, but something else. The same thing but for different reasons. Jim determined to try, at the first opportunity, to probe into that big Martian's mind. Now they were speeding into the real Polar vastness. Kaarji's sled ahead of them dipped and rose across long icy undulations. The terrain was wide and white and peaceful as far as Jim could see. He began to wonder why men had never been able to penetrate very far up here. Even afoot it ought not to be hard, but this was ridiculously easy! As he huddled there in his place on the sled he was very warm and cozy beneath his coat of Praaka fur. He began to get drowsy.... * * * * * Jim awoke with a start from the deep, firm depths of somnolence. He was aware that they had been moving for a long time, probably many hours. Now the sky was dark above him and he could see a few stars. But _something_ had shattered his drowsiness to jerk him back to reality, and he wondered what it was. Then he knew, as it came again. There was a sudden movement beneath them. The sled lurched crazily. Conley was shouting something, as their sled pulled up beside Kaarji's, which was lying half on its side. The men stepped down. Again there came that sudden movement, and Jim nearly fell! Startled, he looked down and saw that the very ice cap was moving beneath their feet, or rather it was expanding! Long lines began to appear in every direction. As far as he could see, the surface was a vast mosaic pattern. Conley stood there with his hands on his hips, staring around. Wessel was cursing softly and looked angry. "This wouldn't have happened," Wessel said, "if you'd taken my advice and left two days ago! Tomorrow it'll be worse. It'll slow us to a walk. We may as well not have brought along any sleds." "It would've happened anyway!" Conley snapped testily. "It's just our damnable luck that it had to come early this year. I didn't expect this to start for another month yet. Well, we may as well camp here and get a good start in the morning." Jim looked at the mosaic pattern across the ice and was relieved to see that it had stopped moving. He peered down into a crack an inch wide, where a billowing powdery stuff exuded to spread thinly over the surface. He touched the stuff with his bare hand. It was uncannily different from snow, being infinitely more powdery yet dazzling white and deadly cold.