ADVENTURES OF CAPTAIN HORN
each other. These rows of little humps were on opposite sides of the dome, and from, the bottom nearly to the top. It was plain they were intended to serve as rude ladders by which the top of the mound could be gained.
The captain stepped back, held up his lantern, and gazed in every direction. He could now see the roof of the cavern, and immediately above him he perceived what he was sure were regular joints of masonry, but on the sides of the cave he saw nothing of the sort. For some minutes he stood and reflected, his brain in a whirl. Presently he exclaimed:
"Yes, this cave is man's work! I am sure of it. It is not natural. I wondered how there could be such a cave on the top of a hill. It was originally a gorge, and they have roofed it over, and the bottom of the basin has been cut out to make it deeper. It was made so that it could be filled up with water, and roofed over so that nobody should know there was any water here, unless they came on it by means of the passage from our caves. That passage must have been blocked up. As for the great opening in the side of the cave, the rocks have fallen in there—that is easy enough to see. Yes, men made this cave and filled it with water, and if the water were high enough to cover the handle of that machine, as it was when I struck it, it must also have been high enough to cover up this stone mound. The lake was intended to cover and hide that mound. And then, to make the hiding of it doubly sure, the men who built all this totally covered up the lake so that nobody would know it was here. And then they built that valve apparatus, which was also submerged, so that they could
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