He worked slowly and carefully, keenly aware of his danger. Gradually, as the flame grew stronger, he increased the size of the twigs with which he fed it. He squatted in the snow, pulling the twigs out from their entanglement in the brush and feeding directly to the flame. He knew there must be no failure. When it is seventy-five below zero, a man must not fail in his first attempt to build a fire--that is, if his feet are wet. If his feet are dry, and he fails, he can run along the trail for half a mile and restore his circulation. But the circulation of wet and freezing feet cannot be restored by running when it is seventy-five below. No matter how fast he runs, the wet feet will freeze the harder.

     All this the man knew. The old-timer on Sulphur Creek had told him about it the previous fall, and now he was appreciating the advice. Already all sensation had gone out of his feet. To build the fire he had been forced to remove his mittens, and the fingers had quickly gone numb. His pace of four miles an hour had kept his heart pumping blood to the surface of his body and to all the extremities. But the instant he stopped, the action of the pump eased down. The cold of space smote the unprotected tip of the planet, and he, being on that unprotected tip, received the full force of the blow. The blood of his body recoiled before it. The blood was alive, like the dog, and like the dog it wanted to hide away and cover itself up from the fearful cold. So long as he walked four miles an hour, he pumped that blood, willy-nilly, to the surface; but now it ebbed away and sank down into the recesses of his body. The extremities were the first to feel its absence. His wet feet froze the faster, and his exposed fingers numbed the faster, though they had not yet begun to freeze. Nose and cheeks were already freezing, while the skin of all his body chilled as it lost its blood.