To have followed the thern boat across the gleaming water would
have been to invite instant detection, and so, though I was loath
to permit Thurid to pass even for an instant beyond my sight, I
was forced to wait in the shadows until the other boat had passed
from my sight at the far extremity of the lake.

Then I paddled out upon the brilliant surface in the direction they
had taken.

When, after what seemed an eternity, I reached the shadows at the
upper end of the lake I found that the river issued from a low
aperture, to pass beneath which it was necessary that I compel
Woola to lie flat in the boat, and I, myself, must need bend double
before the low roof cleared my head.

Immediately the roof rose again upon the other side, but no longer was
the way brilliantly lighted. Instead only a feeble glow emanated
from small and scattered patches of phosphorescent rock in wall
and roof.

Directly before me the river ran into this smaller chamber through
three separate arched openings.

Thurid and the therns were nowhere to be seen--into which of the
dark holes had they disappeared? There was no means by which I
might know, and so I chose the center opening as being as likely
to lead me in the right direction as another.

Here the way was through utter darkness. The stream was narrow--so