410 Mr. Henry’s Experiments on 
one substance in contact with the gas which is capable of de- 
composing water, viz. charcoal. The union of this body with 
the oxygen of the water would be rendered palpable by the for- 
mation of carbonic acid; but Dr. Austin did not observe that 
any precipitation was occasioned in lime water, by agitating it 
with the electrified gas. On passing up syrup of violets to the 
electrified air, with the expectation of its indicating the volatile 
alkali, as in the experiments of Dr. Austin, no change of co- 
lour took place, though the test was of unexceptionable purity. 
On. examining, however, whether any alteration of bulk had 
been produced in the air by the contact of this liquid, it ap- 
peared that of 709 measures, 100 had been absorbed. Sus- 
pecting that the absorption was owing to the presence of car- 
bonic acid, I introduced some lime water to a volume of the 
expanded gas amounting to 556 measures, when they were 
immediately reduced to 512. The contraction would probably 
have been still more remarkable if the gas had been farther ex- 
panded before the admission of the liquid. The change in the 
lime water was very trifling; but my friend Mr. Rupp, who 
witnessed this as well as several of the other experiments, and 
who is much conversant in the observation of chemical facts, 
was satisfied that, after a while, he saw small flocculi of a pre- 
cipitate on the surface of the mercury. This contraction of 
bulk cannot be ascribed to any other cause than the absorption 
of carbonic acid ; for besides the fact that the colour of syrup 
of violets and of turmeric, which I also tried, were not affected 
by exposure to the electrified gas, I have this objection to the 
absorbed gas being ammoniac, that no diminution either of 
bulk or transparency occurred on the admixture of muriatic 
acid gas with the electrified air; whereas ammoniac would 
