The further process of the formation of ice will be this:—the colds of early winter will freeze all the water that may be in the glacieres from the summer’s thaw, in such caves as do not possess a drainage, and then the frost will have nothing to occupy itself upon but the ice already formed, for no water can descend from the frost-bound surface of the earth. As soon as the snow begins to melt to so great a degree that the fissures are opened up once more, the extremely cold water resulting therefrom will descend through the limestone into a cave perfectly dry, and filled with an atmosphere many degrees below the freezing point, whose frost-power eagerly lays hold of every drop of water which does not make its escape in time by the drainage of the cave. Thus the spring months will be the great time of the formation of ice, and also of the raising of the temperature from some degrees below freezing to the more temperate register at which I have generally found it, viz., rather above than below 32 deg.. Professor Tyndall very properly likens the external atmosphere to a ratchet-wheel, from its property of allowing the passage of hot rays down to the surface of the earth, and resisting their return: it may equally be so described on other grounds, inasmuch as the cold and heavy atmosphere will sink in the winter into the pits which lead to glacieres, and will refuse to be altogether displaced in summer by anything short of solar radiation.
We found the one column of the previous day still standing, though evidently in an unhappy state of decay. The sharpness of its edges was wholly gone, and it was withered and contorted; there were two cracks completely through it, dividing it into three pieces 4 or 5 feet long, which were clearly on the point of coming down. Externally, the day was fine and warm, and so we found the cave comparatively dry, only one drop falling in a minute on to the stone where ninety-six had fallen in the same time the day before. The thermometer registered 32 deg. as the greatest cold of the night, and still stood at that point when we took it up.
We spent some little time in exploring the neighbourhood of the pits, in order to find, if possible, the outlet for the drainage, but the ground did not fall away sufficiently for any source from so low an origin to show itself. The search was suggested by what I remembered of the Glaciere of S. Georges three years before, where the people believe that a small streamlet which issues from the bottom of a steep rock, some distance off, owes its existence to the glaciere.