We climbed, and fell outward upon the platform. The roar was deafening. We crouched, clung and found the head of the ladder, then went down it. There seemed still only spray at the bottom. In the white murk I saw the wet black ground, wet courtyard walls. The crest of a wave engulfed them. We clung to the bottom of the ladder. The water fell away. We leaped, reached the ground, and ran, the spray following us down the declivity. The white abyss into which the water had been falling was nearly filled. I saw, as we turned and ran, the blurred vision of that gigantic crumbling dam. But even that would be very soon but a portion of the torrent. * * * * * The aëro was still unharmed. It seemed, as we climbed to it and started it aloft, that a wall of water swept under us. The car bucked and whirled in the wind; the spray was like a torrential salt rain as we mounted through it. We had to shout above the roar. “You think you can guide us out, Tad?” “Yes, I think so.” “We’ve got to get to the tunnel and find Arturo and Nereid.” The water raced us. We rose perhaps five hundred feet. This abyss of the monsters now was not silent, nor dark. Behind us we could hear the roar and lash of the water pouring in. The dark, dying sea was whipped into fury, and rising visibly. The turmoil of water was white now. The white radiance streamed from it. I saw, far overhead, a rocky ceiling. I looked back. The radiance showed the clifflike wall back there, blurred by the white chaos; but I saw it crumbling. We found the connecting passage leading out to the abyss of the Middge and Gians. The water had reached here--the first surge racing through here, a mile-wide subterranean torrent. We flew close over it. There was a place where the ceiling came down. We barely got through. Racing, with the abyss behind us breaking under the pressure. Distant, muffled rumbling, horribly gigantic, behind us. There was a vague muffled explosion off somewhere--some fire-pit which the water had reached. The vibration of it--the suddenly increased air pressure--dashed our aëro into a wild upward leap, and then a drop. We barely recovered, and raced on. The torrent here in the passage was eating at the walls. One of them broke through as we went by. A rock mass fell close behind us. The water backed against it; it broke sidewise in other places. A chaos of falling rock was back there. The dammed-up water turned other ways, into other abysses--filled them, soon rose, pursuing us again. “Where are we, Tad?” I shouted it as we lay prone, clinging to the leaping little aëro. “In the main abyss, I think. God, Jeff, look over there!” We seemed rushing through the familiar abyss of the Mound City. But it was no longer familiar. I followed Tad’s gaze, and saw a red glare in the distance. “Is that the fire caldron?” “I don’t know--I think so--or was it the other way?”