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.
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