Georges.[198] At the
commencement of the hot season, the atmospheric temperature of the
glacieres rises gradually; and when it has almost reached 32 deg. F., the
prismatic change takes place in the ice, extending to a limited depth
below the surface. The central parts of the stalactites retain their
ordinary structure, and are after a time exposed to a general
temperature rather above than below the freezing point; and thus they
come to melt, the water escaping either by accidental fissures between
some of the prisms, or by the extremity of the stalactite, or by some
part of the surface which has chanced to escape the prismatic
arrangement, and has itself melted under increased temperature.[199]
M. Hericart de Thury describes the peculiar structure of the ice which
he found in the Glaciere of the Foire de Fondeurle.[200] He found that
the crystallised portions were very distinctly marked, displaying for
the most part a six-sided arrangement; and in the interior of a hollow
stalactite he found numerous needles of ice perfectly crystallised, the
crystals being some triangular and some six-sided.
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