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.

"When I slipped and sank," he said to himself, "I pulled down that lever,
and I opened the water-gate and let out the lake."

The captain was a man whose mind was perfectly capable of appreciating
novel and strange impressions, but with him such impressions always
connected themselves, in one way or another, with action: he could not
stand and wonder at the wonderful which had happened--it always suggested
something he must do. What he now wanted to do was to climb up to the
great aperture which lighted the cavern, and see what was outside. He
could not understand how the lake could have gone from its basin without
the sound of the rushing waters being heard by any one of the party.

With some difficulty, he climbed up to the cleft and got outside. Here he
had a much better view of the topography of the place than he had yet
been able to obtain. So far as he had explored, his view toward the
interior of the country had been impeded by rocks and hills. Here he had
a clear view from the mountains to the sea, and the ridge which he had
before seen to the southward he could now examine to greater advantage.
It was this long chain of rocks which had concealed them from their
enemies, and on the other side of which must be the ravine in which the
Rackbirds had made their camp.