December, 1882, at the stations where observations were made of the
transit of Venus by astronomers sent out by the French government,
yield the average, for all stations north of the equator to latitude
29° 54' in Florida, 28.2 volumes carbonic acid in 100,000 volumes air,
and for all stations south of the equator 27.1 volumes. The average of
Claesson's[6] estimations is 27.9 volumes, his maximum number is 32.7,
and his minimum is 23.7. It is apparent, from the results of
estimations of carbonic acid of the air of various parts of the globe,
by the employment of apparatus with which errors are avoided, that the
quantity of carbonic acid is subject to slight variation, and not, as
stated in nearly all text books of science, from 4 to 6 volumes in
10,000 volumes of air; and it is further apparent that the law of
Schloesing[7] holds good. By this law the carbonic acid of an
atmosphere in contact with water containing calcium or magnesium
carbonate in solution is dissolved according to the tension of the
carbonic acid; that is, by an increased quantity its tension
increases, and more would pass in solution in the form of
bicarbonates. On the other hand, by diminishing the quantity of
carbonic acid in the atmosphere, some of the bicarbonates would
decompose and carbonic acid pass into the atmosphere.

[Footnote 2: Comptes Rendus, 88, 1007.]
[Footnote 3: Comptes Rendus, 90, 1144.]
[Footnote 4: Chem. Centralblatt, 1872 and 1875.]
[Footnote 5: Comptes Rendus, 96, 1793.]
[Footnote 6: Berichte der deutsch chem. Gesellschaft, 9, 174.]
[Footnote 7: Comptes Rendus, 74, 1552, and 75, 70.]

Schloesing's law has been verified by R. Engel[8].