together with its Analysis. — 237 
cold situation; and as the inclosed air acquired the temperature 
of the surrounding medium, the interior of the glass tube, occu- 
pied by it, became gradually covered with moisture, which at 
length ran down in strie. Now, as the vessels, and the substance 
contained in the bulb, were carefully freed from superficial 
moisture, the water could only be derived from the Arragonite 
used in the experiment. Lime-water was then admitted to the 
air confined over the mercury, but produced no precipitate. 
Hence it is evident that carbonic acid gas was not present, at 
least in any sensible quantity. On a further examination of this 
elastic fluid, it was found to be merely atmospheric air, which had 
been expanded out of one vessel into the other during the opera- 
tion. ‘Thus it appears that Arragonite, when exposed to a de- 
gree of heat inferior to that which is requisite to calcine it, gives 
out water, and, at the time of its expulsion, reduces the calca- 
reous substance to a white, opaque powder, and that without 
decrepitation*. Hence it is inferred that the water contained in 
the mineral is chemically combined with its constituents ; for, if 
otherwise, it would exhibit the same phenomenon of decrepita- 
tion which attends the extrication of water from calcareous spar, 
when exposed to the action of heat. 
Experiment 2.—When water is present in common calcareous 
spar, it occupies only certain interstices, from which it may be 
easily expelled at a low temperature, and even without affecting 
its general transparency. Arragonite, on the contrary, when 
deprived of its aqueous particles by a slight degree of heat, loses 
all its transparency ; from which it may be concluded that these 
* The analyses of Arragonite and of calcareous Spar, by Thenard and Biot, show that the 
quantity of water contained in the former exceeds that of the latter—Mem. d’Arcueil, ii, 
176; - heal 
212 particles 
