The air
contains in oxygen the first element of physical animal life, and besides
this benefit, it possesses another, which may be said to be of a nearly
equally high character, namely, that of conveying sound; a faculty by which
it likewise becomes the conveying sound; a faculty by which it likewise
becomes the conveyer of speech and the means of communicating thought, and
consequently of maintaining social intercourse. If the Earth were deprived
of an atmosphere, as we suppose our moon to be, it would present itself to
our imagination as a soundless desert.
The relative quantities of the substances composing the strata of air
accessible to us have, since the beginning of the nineteenth century, become
the object of investigations, in which Gay-Lussac and myself have taken an
active part; it is however, only very recently that the admirable labors of
Dumas and Boussingault have, by new and more accurate methods, brought the
chemical analysis of the atmosphere to a high degree of perfection.
According to this analysis, a volume of dry air contains 20.8 of oxygen, and
79.2 of nitrogen, besides from two to five thousandth parts of carbonic acid
gas, a still smaller quantity of carbureted hydrogen gas,* and, according to
the important experiments of Saussure and Liebig, traces of ammoniacal
vapors,** from which plants derive their nitrogenous contents.
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