e, if one exists, for ever unsolved. But tonight
my interest has returned and my nerves grown more steady. Tomorrow I
trust that I shall have gone more deeply into this matter.

April 22.--Let me try and set down as accurately as I can my
extraordinary experience of yesterday. I started in the afternoon, and
made my way to the Blue John Gap. I confess that my misgivings
returned as I gazed into its depths, and I wished that I had brought a
companion to share my exploration. Finally, with a return of
resolution, I lit my candle, pushed my way through the briars, and
descended into the rocky shaft.

It went down at an acute angle for some fifty feet, the floor being
covered with broken stone. Thence there extended a long, straight
passage cut in the solid rock. I am no geologist, but the lining of
this corridor was certainly of some harder material than limestone, for
there were points where I could actually see the tool-marks which the
old miners had left in their excavation, as fresh as if they had been
done yesterday. Down this strange, old-world corridor I stumbled, my
feeble flame throwing a dim circle of light around me, which made the
shadows beyond the 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