seemed to have elapsed, during which they had climbed,
descended, squeezed through narrow upright cracks, and crawled, as the
two lads had crawled before, ere they reached the limpid pool where
their guides had rested and gone to sleep.

Here, at a word from Mark, Sir Edward gave the word to halt for
refreshment, while, in company with the two lads, he made a farther
advance, and planted two men at intervals along the route they took,
following the flow of the underground stream, whose musical gurgling
grew very plain at times.

The second man was posted a good two hundred yards beyond the first, and
made no objection to being left in the dark, showing Dan Rugg's wisdom
in selecting miners for the task in hand.

Then, silently and with great caution, Dummy led on along a wild chasm
of the same nature as others they had passed, and formed, evidently
during some convulsion, the encrinite marble of which the walls were
composed matching exactly, and merely requiring lateral pressure and the
trickling of lime-charged water to become solid once again.

About three hundred yards beyond the last sentinel the trio paused, and
stood listening and gazing as far as they could across a rock chamber
whose sides glittered with double prismatic crystals.

But there was the water gurgling at the bottom of the deep crack along
which they passed--nothing more; and they returned toward the pool, Sir
Edward giving the men a word or two of caution, and then passing on to
the others who were whispering to each other as they ate their food.

It was too good an example not to be followed, and soon after, quite
refreshed, Sir Edward gave the order for a fresh start, the way being
doubly interesting now that it was all fresh ground to the guides. In
addition, it became more difficult, for the formation began now to
change, and instead of being a succession of narrow crack-like
passages--in almost every variety of inclination between the horizontal
and perpendicular, and rock grotto-like chambers of varying extent--the
road began to fork and break up into vast halls, from which more than
once they could hardly find an exit.

But Dummy was invaluable, and there was a kind of triumph in his face
when he pointed out how easy it was to go on if you listened for the
trickling of the stream below.

At last, after passing through a long succession of scenes that were as
wondrous as strange, Sir Edward called upon the boy to stop, and upon
Dumm