“Man, since you have been in this part of the country, have you ever seen or heard of any wild beasts here?  Are there any jaguars or pumas?”

The African shook his head.  “No, no,” said he, “no wild beasts.  Everybody sleep out of doors.  No think of beasts—­no snakes.”

The captain dropped his gun upon the ground.  “Miss Markham!” he exclaimed.  “Mrs. Cliff!  I truly believe we are out of all danger—­that we—­”

But the two ladies had gone inside, and heard him not.  They appreciated to the full the danger from which they had been delivered.  Ralph, too, had gone.  The captain saw him on his post of observation, jamming the end of his flagpole down between two rocks.

“Hello!” cried the boy, seeing the captain looking up at him, “we might as well have this flying here all the time.  There is nobody to hurt us now, and we want people to know where we are.”

The captain walked by the little group of Africans, who were sitting on the ground, talking in their native tongue, and entered the passage.  He climbed over the barrier, and went to the lake.  He did not wish to talk to anybody, but he felt that he must do something, and now was a good time to carry out his previous intention to cross over the empty bed of the lake and to look out of the opening on the other side.  There was no need now to do this for purposes of vigilance, but he thought that if he could get out on the other side of the cave he might discover some clew to the disappearance of the lake.

He had nearly crossed the lake bottom, when suddenly he stopped, gazing at something which stood before him, and which was doubtless the object he had struck when swimming.  The sun was now high and the cave well lighted, and with a most eager interest the captain examined the slimy and curious object on which his feet had rested when it was submerged, and from which he had fallen.  It was not the horizontal trunk of a tree with a branch projecting from it at right angles.  It was nothing that was natural or had grown.  It was plainly the work of man.  It was a machine.

At first the captain thought it was made of wood, but afterwards he believed it to be of metal of some sort.  The horizontal portion of it was a great cylinder, so near the bottom of the lake that he could almost touch it with his hands, and it was supported by a massive framework.  Prom this projected a long limb or bar, which was now almost horizontal, but which the captain believed to be the thick rod which had stood upright when he clutched it, and which had yielded to his weight and had gone down with him.  He knew now what it was:  it was a handle that had turned.

He hurried to the other end of the huge machine, where it rested against the rocky wall of the cavern.  There he saw in the shadow, but plain enough now that he was near it, a circular aperture, a yard or more in diameter.  Inside of this was something which looked like a solid wheel, very thick, and standing upright in the opening.  It was a valve.  The captain stepped back and gazed for some minutes at this great machine which the disappearance of the water had revealed.  It was easy for him to comprehend it now.