In the middle of August there was no ice on the surface; but
when the loose _debris_ was removed, the most beautiful ice appeared,
and at a little depth all was frozen as hard as if it had been the depth
of winter.[135] The people who work in the neighbourhood declare that
the place remains open, and free from ice or snow, in the greatest cold,
and that no ice begins to form till the month of June. When the writer
of the account in Poggendorff visited the ice-hole, the peasants were in
the habit of carrying large masses of ice down to their houses, through
a temperature of 81 deg. F.
Reich[136] gives a detailed and valuable account of the prevalence of
subterranean ice on the Sauberg, a hill which forms one side of a ravine
near Ehrenfriedersdorf. The surface is about 2,000 feet above the sea,
and its mean temperature, as determined by many careful observations,
about 45 deg. F. There are several tin-mines in this district, and the
extended observations made by the authorities establish the curious fact
that the mean temperature is considerably lower beneath than at the
surface.
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