A moment or so later they took up their march again. The sledges, with their heavy loads, were cumbersome things to drag over the uneven surface of the ice. The men panted and gasped as they threw their weight on the ropes. Teddy felt the air growing colder still, and presently noticed that the mist no longer seemed to be as thick as before. He glanced down at the front of his heavy fur coat. It was covered with tiny white crystals. He held up his hand with the thick mitten on it to form a dark background, and saw numberless infinitesimal snowflakes drifting slowly toward the ice under his feet. His thermometer showed two degrees above zero--and New York, six miles away, was sweltering in August heat! "Not much farther," he called cheerfully. "We're almost there." They panted and tugged on, a hundred and fifty yards more. Then they stopped and stared. Three hundred yards away the great column of steam was issuing from the ice. A hollow hillock of snow and ice rose to a height of twenty feet, like the miniature crater of a volcano. From it, in an unbroken stream, the mass of steam emerged with a roaring, rushing sound. It rose five hundred feet before it broke into the plumelike formation that was so characteristic. There was a space, perhaps six hundred paces across, in which there was no mist. The cold was too intense to allow of the formation of fog. Water vapor condensed instantly in that frigid atmosphere. But around the clearing the mist rose from the surface of the ice. It became noticeable when it was merely waist-high, then rose to the height of a man, and climbed to a height of fifty feet in a circular wall all about the strange white open space. Teddy, looking at the top of the wall of vapor, saw that it undulated gently, as if waves were flowing back and forth around the tall column of steam. The men began to unload their sledges. The awkward little trench mortars were set in place and careful measurements made of the distance to the steam plume. While the men labored, Teddy moved forward toward the central cone. Five degrees below zero, fifteen degrees below zero, thirty degrees below zero----His breath cut sharply when it went into his lungs. Teddy put his mittened hand over his nose and face to partially warm the air before he breathed it in. Now, even through the heavy, arctic clothing he wore, he felt the bitter cold. He detached the thermometer from his sleeve and clumsily tied it to a cord. He had hoped to be able to lower it down the rim of the crater, but that was impossible. He flung it toward the hillock of snow and ice, let it remain there an instant, then hastily drew it back to read it. The ether in the thermometer had frozen into a solid mass in the bulb of the instrument.