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NOTES
T O
T H E F IRST VOLUME .
C h a p . L p. 25.
La Mere Chantal was the grand-mother of the celebrated
Madame Sevigné, so well known by her letters.
C h a p . VIII. p. 302.
Temperature o f the Earth.
The anhydrous gypsum at Bex, according to the
observations of M .Charpentier, combines with water very
rapidly ; in the Tarentaise this process is slower, for I
observed anhydrous gypsum unchanged, in situations
where it had been long exposed to the atmosphere. The
rapid combination of the anhydrous gypsum with water
at Bex must necessarily give out heat, as caloric is
evolved in all cases where water passes to a solid state
by combining with other substances. This circumstance
has been entirely overlooked by philosophers, who
refer to the increase of temperature in the salt mines of
Bex (ascertained by Saussure) as furnishing proofs of
the high internal temperature of the earth. The experiments
of Saussure have been regarded as particularly
free from any source of error, as there is no metallic
ilecomposition going on in these mines ; but this more