directly to the atomic weights. So the confirmation of this
essential point by chemists of such authority gave the strongest
confirmation to the atomic theory.

During these same years the rising authority of the French
chemical world, Joseph Louis Gay-Lussac, was conducting
experiments with gases, which he had undertaken at first in
conjunction with Humboldt, but which later on were conducted
independently. In 1809, the next year after the publication of
the first volume of Dalton's New System of Chemical Philosophy,
Gay-Lussac published the results of his observations, and among
other things brought out the remarkable fact that gases, under
the same conditions as to temperature and pressure, combine
always in definite numerical proportions as to volume. Exactly
two volumes of hydrogen, for example, combine with one volume of
oxygen to form water. Moreover, the resulting compound gas
always bears a simple relation to the combining volumes. In the
case just cited, the union of two volumes of hydrogen and one of
oxygen results in precisely two volumes of water vapor.

Naturally enough, the champions of the atomic theory seized upon
these observations of Gay-Lussac as lending strong support to
their hypothesis--all of them, that is, but the curiously
self-reliant and self-sufficient author of the atomic theory
himself, who declined to accept the observations of the French
chemist as valid. Yet the observations of Gay-Lussac were
correct, as countless chemists since then have demonstrated anew,
and his theory of combination by volumes became one of the
foundation-stones of the atomic theory, despite the opposition of
the author of that theory.