One of De Saussure's experiments, in the course of his investigation of
the phenomena and causes of cold currents in caves, is worth recalling.
He passed a current of air through a glass tube an inch in diameter,
filled with moistened stones, and by that means succeeded in reducing
the temperature of the current from 18 deg. C. to 15 deg. C.; and when the
refrigerated current was directed against a wet-bulb thermometer, it
fell to 14 deg. C., thus showing a loss of 7 deg..2 F. of heat. No one can see
much of limestone caverns without discovering that the surfaces over
which any currents there may be are constrained to pass, present an
abundance of moisture to refrigerate the currents; and it is not
unreasonable to suppose that the large number of evaporating surfaces,
which currents passing through heaps of debris--such as the basaltic
stones described on page 261--come in contact with, are the main cause
of the specially low temperature observed under such circumstances.
Pictet's theory, however, did not convince all those into whose hands
his paper fell, and M.
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