“He did! Distinguished Service Medal,” March said. “And the Lung is one of the biggest things ever invented to make subs safer. Simple—really, like most good things. The good thing about it is that there’s no connection at all with the outside. Most such devices had a valve system for letting the exhaled air out into the water. But the valves jammed shut—or open—too often. There’s nothing like that to go wrong in the Momsen Lung.” “How does it get rid of the carbon dioxide that you breathe out?” Stan asked. “There’s a can of CO(2) absorbent inside it, that’s all,” March explained. “Of course, in time it wouldn’t absorb any more, but how long are you ever going to use a Momsen Lung at one stretch, anyway?” “Ten or fifteen minutes, I suppose,” Stan replied. “Sure,” March agreed. “And the can of absorbent can take care of your carbon dioxide for a lot longer than that. And the rest of it is really just as simple. It’s an airtight bag that straps over your chest. There’s a mouthpiece you clamp between your teeth for breath, and a nose clip to close your nose so you won’t breathe through it. When the bag’s filled with oxygen—there you are!” “Wonderful!” Stan said. “But doesn’t that bag of oxygen, plus your own tendency to float, send you shooting up to the surface in a hurry?” “It would if you let it,” March replied. “That’s why there always has to be a line or cable up to the surface, so you can hold on to it and keep yourself from ascending too quickly.” “And get the bends,” Stan concluded. “If anything, I know I’ll go more slowly than they tell me.” The next morning they had a chance to look more closely at the Momsen Lungs before they put them on, with the instructor explaining their workings and showing the students how to adjust them. March did not see Scott, the radioman, among the group, although all the others were the same that had gone through the pressure test the day before. He spoke to the young pharmacist, asking about Scott. “Got a cold,” was the reply. “Just a little nose cold, but they wouldn’t let him do the escape test with it.” “Too bad,” March said. “But he’ll be able to catch up with the rest of us soon.” The Chief Petty Officer in charge was explaining the test to the men, as they got into their swimming trunks. “First we’ll have twenty pounds of pressure in the chamber,” he said, “just to be sure noses and ears are in good shape before going into the water. And then you’ve got a long climb ahead of you. You see, the bottom of this tower is a hundred feet from the surface at the top. You won’t be taking the hundred-foot escape for quite a while yet. Today we go up to the eighteen-foot level.”