The river there was a mass of ice from one shore to the other. All the little reedy islands and the swampy shores were frozen solidly. To see the slender palm trees rising from icy shores, their reflections visible on the narrow strip of mist-free ice that ran along the shores of the river was an anomaly. To see fur-clad tourists stepping out of the tropical foliage to step gingerly out on the ice "just to say they'd done it" was even more strange. At the moment, however, interest centered on a little group of soldiers out in the central clearing in the cloud of mist. They were bundled in furs and swathed in numberless garments until they looked like fat penguins or some strange arctic animals. A major of engineers was waving them to the right and left, forward and back until they stood at equal distance around the clearing. Each man moved backward until the mist that rose gradually from the ice reached his waist. Then, at a whistle signal from the major, they began to move forward toward a common center. The major had reasoned that the cold bomb must be precisely underneath the exact center of the clearing, and this was a rough-and-ready means of finding that center. They advanced toward each other, and as they went nearer the center of the clearing the cold grew more intense. Infinitesimal ice crystals glittered in little clouds where the moisture of their breath froze instantly in the terrific cold. At a second whistle from the major they halted. They formed a fairly even circle about forty yards across. Each man began to stamp and fling his arms about to keep from freezing in that more than frigid atmosphere. No man could have stood that cold, no matter how hardy he might be, for more than a very few moments. The major trotted around the circle, marking the place where each man stood. Four small sledge loads of explosives stood out in the clearing. The major intended to blast down toward the cold bomb with them. The major was marking the position of the last man, completing his circle under which the cold bomb must lie, when a peculiar tremor was felt by every man there. It was not like the shiver of an earthquake or the reverberation of an explosion. It was an infinitely shrill vibration that a moment later was followed by a creaking sound that seemed to come from the center of the ice cake. The men on the ice stopped their stamping and swinging of arms to listen in instinctive apprehension.