d Bradley, "I should say higher; but where does it come
from?"

"That is easily discovered now that we have found it," I answered. "It
can't come from the ocean; so it must come from the land. All that we
have to do is follow it, and sooner or later we shall come upon its
source."

We were already rather close in; but I ordered the U-33's prow turned
inshore and we crept slowly along, constantly dipping up the water and
tasting it to assure ourselves that we didn't get outside the
fresh-water current. There was a very light off-shore wind and
scarcely any breakers, so that the approach to the shore was continued
without finding bottom; yet though we were already quite close, we saw
no indication of any indention in the coast from which even a tiny
brooklet might issue, and certainly no mouth of a large river such as
this must necessarily be to freshen the ocean even two hundred yards
from shore. The tide was running out, and this, together with the
strong flow of the freshwater current, would have prevented our going
against the cliffs even had we not been under power; as it was we had
to buck the combined forces in order to hold our position at all. We
came up to within twenty-five feet of the sheer wall, which loomed high
above us. There was no break in its forbidding face. As we watched the
face of the waters and searched the cliff's high face, Olson suggested
that the fresh water might come from a submarine geyser. This, he
said, would account for its heat; but even as he spoke a bush, covered
thickly with leaves and flowers, bubbled to the surface and floated off
astern.

"Flowering shrubs don't thrive in the subterranean caverns from which
geysers spring," suggested Bradley.

Olson shook his head. "It beats me," he said.

"I've got it!" I exclaimed suddenly. "Look there!" And I pointed at
the base of the cliff ahead of us, which the receding tide was
gradually exposing to our view. They all looked, and all saw what I
had seen--the top of a dark opening in the rock, through which water
was pouring out into the sea. "It's the subterranean channel of an
inland river," I cried. "It flows through a land covered with
vegetation--and therefore a land upon which the sun shines. No
subterranean caverns produce any order of plant life even remotely
resembling what we have seen disgorged by this river. Beyond those
cliffs lie fertile lands and fresh water--perhaps, game!"

"Yis, sir," said Olson, "behoin