e, not very deep nor wide,
and from its general trend toward the east and south the captain was sure
that it formed the upper part of the ravine of the Rackbirds. At the
bottom of it there trickled a little stream. To the northeast ran another
line of low rock, which lost itself in the distance before it blended
into the mountains, and at the foot of this must run the stream which had
fed the lake.

In their search for water, game, or fellow-beings, no one had climbed
these desolate rocks, apparently dry and barren. But still the captain
was puzzled as to the way the water had gone out of the lake. He did not
believe that it had flowed through the ravine below. There were no signs
that there had been a flood down there. Little vines and plants were
growing in chinks of the rocks close to the water. And, moreover, had a
vast deluge rushed out almost beneath the opening which lighted the cave,
it must have been heard by some of the party. He concluded, therefore,
that the water had escaped through a subterranean channel below the rocks
from which he looked down.

He climbed down the sides of the gorge, and walked along its bottom for
two or three hundred yards, until around a jutting point of rock he saw
that the sides of the defile separated for a considerable distance, and
then, coming together again below, formed a sort of amphitheatre. The
bottom of this was a considerable distance below him, and he did not
descend into it, but he saw plainly that it had recently contained water,
for pools and puddles were to be seen everywhere.

At the other end of it, where the rocks again approached each other, was
probably a precipice. After a few minutes' cogitation, Captain Horn felt
sure that he understood the whole matter: a subway from the lake led to
this amphitheatre, and thus there had been no audible rush of the waters
until they reached this point, where they poured in and filled this great
basin, the lower end of which was probably stopped up by accumulations of
sand and deposits, which even in that country of scant vegetation had
accumulated in the course of years. When the waters of the lake had
rushed into the amphitheatre, this natural dam had held them for a while,
but then, giving way before the great pressure, the whole body of water
had suddenly rushed down the ravine to the sea.

"Yes," said the captain, "now I understand how it happened that although
I opened the valve at noon, the water did not reach the R