"We must be pretty nearly at the cold bomb now," said Teddy thoughtfully. "There's a mass of liquid air at the bottom of our crater, and something tells me there's solidified air at the bottom of that puddle. That means seven hundred-odd degrees below zero." He was clad in the warmest garments that could be found, and every one of the others working in the clearing was quite as warmly clothed, but the cold was intense. One of the soldiers by the small pile of explosives was chewing a cud of tobacco. He spat. The brownish liquid froze in mid-air and bounced merrily away across the ice. The soldier looked at it with his mouth open, then shut it quickly. A thin film of ice had formed from the moisture on his teeth. The breast of every member of the party was covered with sparkling snow crystals from the congealed moisture of their breath. "I begin to doubt if we can keep our stuff from freezing much deeper," Teddy commented. "We want to go down as deep as we can before we use our Dewey bulbs, though. I've only two of them." The young lieutenant bustled away, and presently returned. "The men say that the last bomb won't go off," he said aggrievedly. "Your heating plan doesn't work." "I didn't expect it to work indefinitely," said Teddy mildly. "We want to clear out that liquid air and shoot our two Dewey globes before it's had time to reform. Will you please have a charge made ready to be fired just above the surface of that puddle? That should clear it away. Immediately after that charge has gone off we'll drop our two T. N. T. charges in the Dewey bulbs. They ought to show us the cold bomb." The dynamite charge was suspended about a foot above the surface of the watery, bubbling pool. Air was in that pool, air turned to transparent liquid by the intense cold. At -325° Fahrenheit air becomes a liquid. Here, exposed to the sunlight and the blue sky, a pool of liquified gas had collected from the incredible cold of the cold bomb below. The charge of explosive burst with a shattering roar. The echoes of the explosion had not died away when the two Dewey bulbs filled with T. N. T. fell into the bared ice cavity. A Dewey bulb is a combination of six vacuum bottles placed one outside the other. They are used for the keeping of liquid gases at a low temperature, but are obviously just as effective in protecting their contents from exterior cold. They fell some five yards apart and rolled, then were still. Their fuses sputtered. They went off together. A huge mass of shattered ice was thrown aside, and a dark, globular mass was exposed to view. Almost as soon as it was exposed to the air a crust of frozen air coated it, and liquified air began to trickle down its misshapen sides. There could be no doubt but that it was the cold bomb, invented by an insane genius to make him master of the world.