The centre was sufficiently lighted by the day; but in the western corner, and behind the largest column, artificial light was necessary.

The ice itself did not generally show signs of thawing, but the whole cave was in a state of wetness, which made the process of measuring and investigating anything but pleasant.
I had placed two thermometers at different points on my first entrance--one on a drawing-board on a large stone in the middle of the pond of water which has been mentioned, and the other on a bundle of pencils at the entrance of the end chapel, in a part of the cave where the ice-floor ceased for a while, and left the stones and rock bare.

The former gave 33 deg., the latter, till I was on the point of leaving, 31 1/2 deg., when it fell suddenly to 31 deg..

It was impossible, however, to stay any longer for the sake of watching the thermometer fall lower and lower below the freezing point; indeed, the results of sundry incautious fathomings of the various pools of water, and incessant contact of hands and feet with the ice, had already become so unpleasant, that I was obliged to desert my trusty hundred feet of string, and leave it lying on the ice, from want of finger-power to roll it up.

The thermometers were both Casella's, but that which registered 31 deg.