They had no way of measuring time, and Rawson could only guess at the hours that passed while their little ship tore swiftly upward through the dark. He wondered if the occasional shrill shriek that followed the touching of their metal guides on the glassy walls could be heard up above. Then, at last, Loah was driving the _jana_ slowly while she held her light so it would shine through a window. Rawson had to restrain himself to keep from pacing the little room like a caged animal while the precious minutes slipped by. Now that the enemy was near he wanted nothing but to drive on up to the end of the shaft, come out into that world wherever the shaft ended, then try to fight his way through to the great hall where he hoped to find Phee-e-al. And his haste made him overestimate the passing time; their journey had been swifter than he knew. "I may have passed it," Loah was saying doubtfully. "I may have come too far." Then she interrupted herself and sprang to the controls. They drifted slowly back. "It is different now," Loah said; "the air rises more swiftly than before." She stared from the windows while she drove the _jana_ slowly up and down, trying to bring it to equilibrium in the strong up-draft. The air entered the shell through a little opening with the same pungent tang Rawson had noticed before. He had wondered about the air. Down near the neutral zone it was dense, yet he had not minded the pressure too greatly--and that had been puzzling. "Rock pressure and air pressure," he had reasoned; "they are two different things. If the rock flowed, any air that it trapped would be squeezed to a liquid. But it doesn't flow--that red stuff is solid; so the air pressure is only the weight of the air column itself. But even that should be enormous." He could only conclude that the lessened pressure came from that strange counter-gravitation, the repelling force from the center of the earth. Perhaps it tended to dissipate the molecules, held them farther apart, prevented their squeezing in together, and battering with a thousand little impacts on a point where one had hit before. Their _jana_ swayed gently as if the smooth air currents were disturbed and were drifting them sideways; and then, at last, Loah, peering from a window, sprang back and moved a lever. Beneath them was the softly-cushioned thud of the shell seating itself on firm rock. * * * * * They were in another of the interminable caves, Rawson found when he opened the door. The _jana_ was resting a few feet in from the edge of the shaft. Cautiously they got out, but even without their weight it had a slight negative buoyancy. "Oro is pulling more strongly than Grah," Dean said, and smiled. Already the names seemed familiar to him. The two lifted the _jana_ and carried it back some twenty feet more before Rawson realized how unnecessary this was.