He could not appreciate the full significance of the velocities Arcot had told him about--he only knew that he had made a bad mistake in underrating the powers of this ship! "I will not touch these things again without your permission, Earthman," Torlos promised earnestly. The _Ancient Mariner_ drove on through space, rapidly eating up the millions of miles that separated Nansal from Sator. Arcot sat in the control room with Morey discussing their passenger. "You know," Arcot mused, "I've been thinking about that man's strength; an iron skeleton doesn't explain it all. He has to have muscles to move that skeleton around." "He's got muscles, all right," Morey grinned. "But I see what you mean; muscles that big should tire easily, and his don't seem to. He seems tireless; I watched him throw those men one after another like bullets from a machine gun. He threw the last one as violently as the first--and those men weighed over three hundred pounds! Apparently his muscles felt no fatigue!" "There's another thing," pointed out Arcot. "The way he was breathing and the way he seemed to keep so cool. When I got through there, I was dripping with sweat; that hot, moist air was almost too much for me. Our friend? Cool as ever, if not more so. "And after the fight, he wasn't even breathing heavily!" "No," agreed Morey. "But did you notice him _during_ the fight? He was breathing heavily, deeply, and swiftly--not the shallow, panting breath of a runner, but deep and full, yet faster than I can breathe. I could hear him breathing in spite of all the noise of the battle." "I noticed it," Arcot said. "He started breathing _before_ the fight started. A human being can fight very swiftly, and with tremendous vigor, for ten seconds, putting forth his best effort, and only breathe once or twice. For another two minutes, he breathes more heavily than usual. But after that, he can't just slow down back to normal. He has used up the surplus oxygen in his system, and that has to be replaced; he has run into 'oxygen debt'. He has to keep on breathing hard to get back the oxygen surplus his body requires. "But not Torlos! No fatigue for him! Why? _Because he doesn't use the oxygen of the air to do work, and therefore his body is not a chemical engine!_" Morey nodded slowly. "I see what you're driving at. His body uses the heat energy of the air! His muscles turn heat energy into motion the same way our molecular beams do!" "Exactly--he lives on heat!" Arcot said. "I've noticed that he seems almost cold-blooded; his body is at the temperature of the room at all times. In a sense, he is reptilian, but he's vastly more efficient and greatly different than any reptile Earth ever knew. He eats food, all right, but he only needs it to replace his body cells and to fuel his brain."