The string was always catching at something, and mere progression,
without any string to manage, would have been difficult enough under the
circumstances. It was completely dark, so a candle occupied one hand,
and, as every step must be cut, save where an opportune rock or stone
appeared, an axe occupied the other; then there was the string to be
attended to, and both hands must be ready to clutch at some projecting
point when a slip came, and now and then a ruder rock required
circumvention. Add to all this, that hands and feet had not been
rendered more serviceable by an hour and a half of contact with ice, and
it will easily be understood that I was glad when the measurement was
over. At this point the breadth was 25 yards, and, a few feet above the
line in which I crossed, all traces of rock or stone disappeared, and
there was nothing but unbroken ice. I had of course abundant
opportunities for examining the structure of the ice, and I found in all
parts of the fall the same large-grained material, breaking up, when
cut, into the usual prismatic nuts.

I now rejoined Christian, and we worked our way upwards to the mouth of
the cave, penitently desisting from stoning a remaining raven. We
observed at the very mouth, by watching the flame of the candles, a
slight current outwards, extremely feeble, and on our first arrival I
had fancied there was a current, equally slight, inwards, but neither
was perceptible beyond the entrance of the cave. M. Soret was fortunate
enough to witness a curious phenomenon, at the time of his visit to the
Schafloch, in September 1860, which throws some light upon the
atmospheric state of the cave. The day was externally very foggy, and
the fog had penetrated into the cavern; but as soon as M. Soret began to
descend to the glacière itself, properly so called, he passed down out
of the fog, and found the air for the rest of the way perfectly
clear.[63]