eye, nor do I know whether it existed at all. In the Glacière of La
Genollière I carried a large block of perfectly prismatic ice into the
outer cave, where it was exposed to the free currents of air passing
from the pit of entrance to the hole newly opened by the falling in of
the ground; and, two days after, the external lines were scarcely
perceptible, while on the occasion of our third visit I found that they
had entirely disappeared, and the whole block was rapidly following
their example. This disappearance of the surface-lines under the action
of atmospheric thaw is probably the same thing as their absence when the
flooring of ice is thinly covered with water. Wherever the flooring rose
slightly towards the edges of the sea of ice, the usual structure
appeared again.

There were no currents of air in the cave, the candles burning steadily
through the whole time of our visit. Excepting for the purpose of
detecting disturbance in the air, there is no need of candles, as the
two holes in the roof supply sufficient light. Some account of the
careful observations made here by M. Thury, at different seasons of the
year, will be found in other parts of this book. We passed, on our
return, by the source of water which springs from the foot of a rock at
some distance from the glacière, and is supposed to form the outlet for
the drainage of the cave; but it is difficult to understand how this can
be the case, considering the form and character of the intervening
ground.

The two ice-caves so far described are the least interesting of all that
I have visited; but a peasant informed me, a day or two after, that if
we had penetrated to the back of the pyramid of snow which lay half
under the open hole, being the remains of the large collection which is
formed there in the winter, we might have found a deep pit which is