lakes, and expecting every minute to see a lot of bloodthirsty pirates
bursting in upon us, is enough to shake the nerves of anybody."

"Captain," said Ralph, "I suppose you will not now object to letting me
go in the morning to explore that opening. I can walk across the bottom
of the lake without any danger, you know."

"Don't you try to do anything of the kind," said the captain, "without my
permission."

"No, indeed!" exclaimed Mrs. Cliff. "Supposing the water were to suddenly
rise just as you were half-way across. Now that I think of it, there are
springs and bodies of water which rise and fall this way, some of them in
our own Western country, but none of them are as large as this. What if
it should rise in the night and flood the cave while we are asleep?"

"Why, dear Mrs. Cliff," said Edna, "I am not afraid of the water's rising
or of the earth's sinking. Don't let us frighten ourselves with
imaginations like that. Perhaps there may not even be any real thing to
be afraid of, but if there should be, let us keep courage for that."

The disappearance of the lake gave the captain an uneasiness of which the
others had not thought. He saw it would be comparatively easy for the
Rackbirds to gain access to the place through the cleft in the eastern
wall of the lake cavern. If they should discover that aperture, the
cavern might be attacked from the rear and the front at the same time,
and then the captain feared his guns would not much avail.

Of course, during the darkness which would soon prevail there was no
reason to expect a rear attack, and the captain satisfied himself with