squatting on a steeply sloping descent of large blocks of
stone, while in face of us was a magnificent wall of ice, evidently the
continuation of the wall above, marked most plainly with horizontal
lines. This wall passed down vertically to join the slope on which we
were, at a depth below our feet which the light of the candle had not
yet fathomed. The horizontal bands were so clear, that, if we had
possessed climbing apparatus, we could have counted the number of layers
with accuracy. Of course we scrambled down the stones, and found after a
time that the angle formed by the ice-wall and the slope of stones was
choked up at the bottom by large pieces of rock, one piled on another
just as they had fallen from the higher parts. These blocks were so
large, that we were able to get down among the interstices, in a spiral
manner, for some little distance; and when we were finally stopped,
still the ice-wall passed on below our feet, and there was no possible
chance of determining to what depth it went. The atmosphere at this
point was a sort of frozen vapour, most unpleasant in all respects, and
the candles burned very dimly. The thermometer stood at 32 deg., half-way
down the slope of stones.

We were able to stretch a string in a straight line from the lowest
point we reached, through the interstices of the blocks of stone, and
up to the entrance-hole, and this measurement gave 50 feet.
Considering the inclination of the upper ice-floor, and the sharpness
of the angle between the wall of ice and the line of our descent to
this lowest point, I believe that 50 feet will fairly represent the
height of the ice-wall from this point to the foot of the slope from
the upper wall; so that 72 feet will be the whole depth of ice, from
the top of the third ladder to the point where our further progress
downwards was arrested. The correctness of this calculation depends
upon the honesty of Mignot, who had charge of the farther end of the
string, and was proud of the wonders of his cave. A dishonest man
might easily, under the circumstances, have pulled up a few feet more
of string than was necessary, but 50 feet seemed in no way an
improbable result of the measurement.

[Illustration: SECTION OF THE LOWER GLACIERE OF THE PRE DE S. LIVRES.]

The ice was as solid and firm as can well be conceived. The horizontal
bands would seem to prove conclusively that it was no coating of greater
or less thickness on the face of a vertical wall