Has the composition of the atmosphere changed in the lapse of years?
On this point both French and German philosophers have largely
speculated. It is computed that it contains about two millions of
cubic geographical miles of oxygen, and that 12,500 cubic geographical
miles of carbonic acid have been breathed out into the air or
otherwise given out in the course of five thousand years. The
inference, then, should be, that the latter exists in the air in the
proportion of 1 to 160, whereas we find but 4 parts in 10,000. Dumas
and Bossingault decided that no change had taken place, verifying
their conclusion by experiments founded on observations for more than
thirty-five years. No _chemical_ combination of oxygen and nitrogen
has ever been detected in the atmosphere, and it is presumed none will
be.
* * * * *
The atmosphere possesses, as may be readily imagined, many important
characteristics. One of these is Weight.
This is demonstrated by simple, yet decisive experiments. The
discovery of the _fact_ is attributed to the illustrious Galileo, but
to modern science we owe all the certainty, variety, and elegance of
the demonstration.
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