"Not necessarily; but, if it does, its outlet must be on the shore off which the 'Fortuna' is lying, otherwise it must defy the laws of gravity and climb the hill on our right. My impression is, however, that it falls into a vast chasm, and the basaltic nature of the rocks strengthens my conviction." "That sounds interesting." "It does. As the island is composed largely of basalt, and shows signs of volcanic action, there can be no doubt as to its origin. Thousands of years ago a mighty earthquake must have shot this and hundreds of other islands above the surface, and from the floor of the vast submarine plateau the coral builders are doing their work of making new ground." "Shall we try to trace the course of this stream, then? Yadillah has a large knife, so that we can clear a path through the scrub." "Well, there's no harm in attempting it. Yadillah, you black imp!" "Yas, sahib." "Cut a path for us through this stuff." The Arab attacked the undergrowth vigorously, and, working as he went, disappeared in the tunnel that he had cut above the stream. Presently he returned with the information that the thicket extended only a short way, and that the brook ran through a dense coco-nut grove. "Lead on, then, Yadillah," exclaimed the doctor. "You follow, Reggie, and I'll bring up the rear." "Clear off, you niggers," he added, speaking authoritatively to the natives, who were regarding our movements with ill-concealed excitement. The doctor's words and actions had the desired effect, for the crowd of followers stood back, jabbering incessantly, save a few who made off towards the village. Although we kept our thick water-tight boots on, the water was deliciously cool as we waded down the stream, bending low to escape the rough tendrils that overhung the low tunnel that the Arab had cut for us. A few steps brought us to the other side of the vegetable barrier, and, as Yadillah had said, the brook flowed through a fairly dense palm-grove, its bed being composed of hard, slippery rock. After we had proceeded a few hundred yards the doctor suddenly exclaimed-- "Hullo! This looks interesting. There's a well-worn path here. I suppose it leads to the village." "But why interesting?" "For one reason, there is no actual necessity for the natives to make a well-worn path to the brook, as plenty of water can be had in the village; for another, I think we have stumbled on some secret place where these savages hold their religious ceremonies. I am not sure, mind you, but the circumstances point that way." The path descended abruptly into what appeared to be a vast circular hollow, though the dense clusters of trees and bushes prevented us from seeing the opposite side of the rock-bound circle. The stream now became a rushing torrent, leaping from rock to rock in a series of spray-fringed cascades, and the only sound that broke the silence of the spot was the noise of the falling water.