ment was
this:--In a lateral gallery, connected with the main shaft, but
deserted, and, therefore, unaffected by breath or the heat of lamps, at
321 ft. 10 in. below the surface, the temperature of the water and the
air was exactly the same, 11-1/2 deg.; or, if the centesimal thermometer was
used, 52-4/5 Fahr.; if Reaumur's, 57-7/8 Fahr.

277. In another gallery, 564 feet below the surface, the water and air
had likewise the same temperature, 12-1/2 deg., either 54-4/5 or 6O-1/4
Fahr. The water at the bottom, 677 feet, was 14 deg., 57-1/2 or 63-1/4 Fahr.
The ratio in which the heat increases, therefore, increased as we
descend, since a difference of 113 feet between the depth of the bottom
of the shaft and the lowest gallery makes a greater difference in
temperature than the difference of 243 feet between the lowest and upper
gallery. This heat is the more striking when it is considered that the
water is impregnated with salt; indeed, Saussure appears inclined to
consider it accidental, perhaps occasioned by the combustion of pyrites,
or other causes in the interior of the mountain ("Voyages dans les
Alpes," tom. iv., c. 50). All experiments of this kind, indeed, are
liable to error, from the frequent occurrence of warm springs, and other
accidental causes of increase in temperature. The water at the bottom of
deep lakes is always found several degrees colder than the atmosphere,
even when the water at the surface is warmer: but that may be accounted
for by the difference in the specific gravity of water at different
temperatures; and, as the heat of the sun and atmosphere in summer is
greater than the mean heat of the earth at moderate depths, the water at
the bottom, even if it becomes of the same heat with the earth, must be
colder than that at the surface, which, from its exposure to the sun,
becomes frequently warmer than the air. The same causes affect the
temperature of the sea; and the greater saturation of the water below
with salt renders it yet more susceptible of cold. Under-currents from
the poles, and the sinking of the water of low temperature, which
results from the melting of the icebergs which float into warmer
latitudes, contribute still farther to lower the temperature of the deep
sea. If, then, the temperature of the sea at great depths is found not
many degrees lower than that at the surface, it would be a striking
proof of the effect produced by the heat of the earth; but I am not
aware of the res