Carbonic Acid .004
Carburetted Hydrogen .004
______
10.000

and he adds a trace of Ammoniacal Vapor. It is _usual_ to state the
proportions of air as being 1 Oxygen to 4 Nitrogen.

It is a curious fact, that, while there are six varieties of compounds
of nitrogen and oxygen, but one of these is fitted to sustain life,
and that is our atmosphere.

It is well enough to note, that, when we use the word volume or
measure, in speaking of the atmosphere or any gaseous body, we adopt
the theory of Gay-Lussac, who discovered that gases unite with each
other in definite proportions whenever they enter into combination.
This theory led to important results; for by knowing the elements of a
compound gas, we easily determine its specific gravity.

It has been attempted to apply the principle to organic bodies;
but it has not yet been carried to a full and satisfactory
conclusion. It may be noticed, too, that Dalton affirmed that
simple substances unite with each other in definite weights
to form compound substances, thus supporting the idea of
Lussac. These discoveries were made about the same time,
Dalton having the credit of originating them. Various modifications
of the principle have been from time to time presented to public
attention.

Whether the constituents of the atmosphere are chemically or