And he was right. Inch by inch the magnet rose from the ground--for what ultimate purpose was not very clear, any more than that it was thought necessary by Leighton, in order to discover the use to which this strange bar of metal had been put, first to test the appliance obviously intended to bring it into action. It reached a height of one foot from the ground, then two, then three feet; then it stopped. There were groans and smothered imprecations, and it looked very much as if the huge bar of metal would come crashing down to the ground again. But the men, urged on by Leighton, did not give in. And then--there was a grating noise, as if some hidden mechanism in the scaffolding had been set free. After which a strange thing happened. The transverse beam at the top of the windlass detached itself from one of the uprights supporting it and, using the other upright as a fulcrum, slowly swung to the wall of the cave, where it rested in a socket, bringing the magnet that was suspended from it, directly over a shelf-like projection beneath. "Keep on! Keep on!" cried Leighton encouragingly. "Now we will see." Thoroughly aroused, the others redoubled their exertions. The magnet remained stationary for a few seconds, the liana supporting it tightening with every revolution of the drumhead at which the men were laboring. Then it slowly disappeared downward, the liana uncoiling itself, thus reversing the movement that before had carried it upward. There was a gradual increase in the momentum of its descent, followed by the splashing sound caused by the impact of a heavy body upon the surface of a pool of water; after which the liana was paid out until it reached its full length--when it suddenly slackened and came to a full stop. "There, Mrs. Quayle, is your water," announced Leighton. "Water!" sneeringly echoed a voice from the darkness behind them. "Say, rather, there is the secret of Guatavita!" "Raoul Arthur!" exclaimed the others. Letting go the handle of the windlass, they rushed to the spot where the Black Magnet had vanished. There, at one side of the rocky projection, stood Raoul, pale and haggard, the light in his lamp extinguished. "I suspected this," he said, as if his sudden reappearance among them were the most natural thing in the world. "I knew from the direction of the path that it led back to the lake. I have been trying to reach this place for years. Oh, yes! I had heard something about it before--I don't deny that. But, of course, I expected to stay by you. So, when you started to leave the cave I came back, expecting to rejoin you. As I was examining the machine I was attacked by two men, thrown to the ground and left unconscious. I came to myself a few minutes ago--in time to congratulate you, it seems, upon solving the mystery of the cave."