On Uranus there is no sense trying to make a man adapt to any of the natural divisions of time there, such as the rotation of the moons or the position of the sun; and as long as man is attuned to the artificial twenty-four hour day anyway, that is the most convenient unit of time. You have sixteen hours to yourself, for whatever you want to do--sleeping, reading, playing the visitapes, or anything else that strikes your fancy in the limited space of the air bubble, half of which is always dark and the other half always light. But the other eight hours belong to the company. For six of them you man the pumps or the radio equipment or the cable drum while the other men plunge, and you make your plunges in the other two. When Nils went on duty that day, he was on the radio, and Kerr was down below. The optimism he had felt after his talk with the captain was dissipated. He realized that, after all, the air lions were a disappearing species. He had been here hunting them for six months and had bagged only six. One a month--yet that was the best record of any of the men. And here he was, expecting to get his seventh in the next day or so. Kerr was calling for more cable. Nils reassured him absently and signaled the crew at the drum. The hunter said, "What's the matter, Nils? You don't sound happy." Nils said into the microphone, "Don't worry about me. You watch out for those lions." He glanced at his watch. He had been on duty now only twenty minutes. An hour and forty minutes to go before his plunge. Usually you took it first, in order to be in your best condition, rested and untired. But, because Nils had got out of order owing to his trip upstairs, he had to take his plunge after he had already been on duty for two hours. That was bad. He would be just a little tired. He wouldn't be quite in the right condition. His responses would be just a shade off. The work would be just that much more dangerous. And then he thought, What if I don't get back? What if it's my last plunge? What if I don't get that air lion? What if I die down there, Siegfried unprovided for? Kerr's voice sounded: "I think I see one." "Need anything?" Nils asked. "Not so far. But I think there's something moving down there." "Good luck," Nils said. But his voice was empty. He was thinking of himself. There were so many things that might happen to him down there, and he had only now begun to think of them. * * * * *