They were treading on lava now, vitreous, and smooth as glass. It was impossible to proceed further in that direction. They turned their steps around the base in the direction of the sea. After another hour, during which their way was lit by almost continuous lurid flashes from the crater, a patch of illumination, apparently out at sea, began to become visible. A half hour more, and they were rounding the volcano's base, and suddenly it burst upon them, a stupendous spectacle that drew an exclamation of amazement from Jim's lips. That low, flat background was the sea, the sound of whose breakers was faintly audible. Between sea and land ran a narrow, slender causeway, perhaps a mile in length. And beyond that, set on a small island, was the most splendid city that Jim could have imagined. Like New York--very like New York, with its mighty towers, but more symmetrical, sloping upward from the sea toward a towering rampart at the heart of it, crowned with huge domes and minarets and serpentine ramps and mighty blocks of stone that must have sheltered as many occupants as New York's highest skyscrapers. The whole was snow-white, and gleamed softly in an artificial light dispensed from an enormous artificial planet that seemed to hover above the ramparts. "God!" whispered Jim in awe as he gazed at the great city. "You cannot cross that causeway," whimpered old Parrish. "It's death to try. One sweep of the Ray will blot out every living thing." "Hush! Listen!" came from Lucille's lips. "Something's moving down there!" * * * * * The distant murmur of voices, the indescribable "feel" of the proximity of other human beings told Jim that they were in imminent danger. He glanced about him. A little overhead was an outcrop of enormous boulders, standing up like a little fortress above the smooth lava. "Get behind there!" Jim whispered. They turned and ran, slipping and stumbling up the smooth slope. Reaching the boulders, they ensconced themselves hastily behind them. Jim peered out through a crevice between two of the largest stones. The sound of moving things became more audible. Then, as a flash of flame shot from the crater overhead, Jim saw a black human horde creeping like an array of ants around the base of the mountain not far beneath. Just like an army of warrior ants it seemed to flow onward, in perfect order. And in the midst of it a faint violet light began to be visible. Parrish seized Jim's arm, shaking with terror. "You know what that is, Dent?" he whimpered. "It's Tode's Drilgoes, moving for a night attack upon Atlantis," answered Jim. "And that thing in the middle is the Atom Smasher." * * * * *