more threatening and obscure. Finally, I came to a spot where
the Roman tunnel opened into a water-worn cavern--a huge hall, hung with
long white icicles of lime deposit. From this central chamber I could
dimly perceive that a number of passages worn by the subterranean
streams wound away into the depths of the earth. I was standing there
wondering whether I had better return, or whether I dare venture farther
into this dangerous labyrinth, when my eyes fell upon something at my
feet which strongly arrested my attention.

The greater part of the floor of the cavern was covered with boulders
of rock or with hard incrustations of lime, but at this particular point
there had been a drip from the distant roof, which had left a patch
of soft mud. In the very centre of this there was a huge mark--an
ill-defined blotch, deep, broad and irregular, as if a great boulder had
fallen upon it. No loose stone lay near, however, nor was there anything
to account for the impression. It was far too large to be caused by any
possible animal, and besides, there was only the one, and the patch of
mud was of such a size that no reasonable stride could have covered it.
As I rose from the examination of that singular mark and then looked
round into the black shadows which hemmed me in, I must confess that I
felt for a moment a most unpleasant sinking of my heart, and that, do
what I could, the candle trembled in my outstretched hand.

I soon recovered my nerve, however, when I reflected how absurd it was
to associate so huge and shapeless a mark with the track of any known
animal. Even an elephant could not have produced it. I determined,
therefore, that I would not be scared by vague and senseless fears from
carrying out my exploration. Before proceeding, I took good note of
a curious rock formation in the wall by which I could recognize the
entrance of the Roman tunnel. The precaution was very necessary, for
the great cave, so far as I could see it, was intersected by passages.
Having made sure of my position, and reassured myself by examining
my spare candles and my matches, I advanced slowly over the rocky and
uneven surface of the cavern.

And now I come to the point where I met with such sudden and desperate
disaster. A stream, some twenty feet broad, ran across my path, and I
walked for some little distance along the bank to find a spot where I
could cross dry-shod. Finally, I came to a place where a single flat
boulder lay near the