question whether or not chemical elements unite with one another
always in definite proportions. Berthollet, the great co-worker
with Lavoisier, and now the most authoritative of living
chemists, contended that substances combine in almost
indefinitely graded proportions between fixed extremes. He held
that solution is really a form of chemical combination--a
position which, if accepted, left no room for argument.

But this contention of the master was most actively disputed, in
particular by Louis Joseph Proust, and all chemists of repute
were obliged to take sides with one or the other. For a time the
authority of Berthollet held out against the facts, but at last
accumulated evidence told for Proust and his followers, and
towards the close of the first decade of our century it came to
be generally conceded that chemical elements combine with one
another in fixed and definite proportions.

More than that. As the analysts were led to weigh carefully the
quantities of combining elements, it was observed that the
proportions are not only definite, but that they bear a very
curious relation to one another. If element A combines with two
different proportions of element B to form two compounds, it
appears that the weight of the larger quantity of B is an exact
multiple of that of the smaller quantity. This curious relation
was noticed by Dr. Wollaston, one of the most accurate of
observers, and a little later it was confirmed by Johan Jakob
Berzelius, the great Swedish chemist, who was to be a dominating
influence in the chemical world for a generation to come. But
this combination of elements in numerical proportions was exactly
what Dalton had noticed as early as 1802, and what bad led him