But Haidia's voice, some distance ahead, interrupted Dodd's soliloquy, and, hoisting the beetle-shells upon their backs, they started along the rough trail that they could feel with their feet over the stony ground. It was still as dark as pitch, but soon they found themselves traveling up a sunken way that was evidently a dry watercourse. And now and again Haidia's reassuring voice would come from in front of them. * * * * * The road grew steeper. There could no longer be any doubt that they were ascending toward the surface of the earth. But even the weight of the beetle-shells and the steepness could not account for the feeling of intense weakness that took possession of them. Time and again they stopped, panting. "We must be very near the surface, Dodd," said Tommy. "We've surely passed the center of gravity. That's what makes it so difficult." "Come on," Haidia said in her quiet voice, stretching out her hand through the darkness. And for very shame they had to follow her. On and on, hour after hour, up the steep ascent, resting only long enough to make them realize their utter fatigue. On because Haidia was leading them, and because in the belief that they were about to leave that awful land behind them their desires lent new strength to their limbs continuously. Suddenly Haidia uttered a fearful cry. Her ears had caught what became apparent to Dodd and Jimmy several seconds later. Far down in the hollow of the earth, increased by the echoes that came rumbling up, they heard the distant, strident rasp of the beetle swarm. Then it was Dodd's turn to support Haidia and whisper consolation in her ears. No thought of resting now. If they were to be overwhelmed at last by the monsters, they meant to be overwhelmed in the upper air. * * * * * It was growing insufferably hot. Blasts of air, as if from a furnace, began to rush up and down past them. And the trail was growing steeper still, and slippery as glass. "What is it, Jim?" Tommy panted, as Dodd, leaving Haidia for a moment, came back to him. "I'd say lava," Dodd answered. "If only one could see something! I don't know how she finds her way. My impression is that we are coming out through the interior of an extinct volcano." "But where are there volcanoes in the south polar regions?" inquired Tommy. "There are Mount Erebus and Mount Terror, in South Victoria Land, active volcanoes discovered by Sir James Ross in 1841, and again by Borchgrevink, in 1899. If that's where we're coming out--well, Tommy, we're doomed, because it's the heart of the polar continent. We might as well turn back." "But we won't turn back," said Tommy. "I'm damned if we do." "We're damned if we don't," said Dodd. "Come along please!" sang Haidia's voice high up the slope.