urged its tenability. Coming just after Davy's dissociation of
some supposed elements, the idea proved alluring, and for a time
gained such popularity that chemists were disposed to round out
the observed atomic weights of all elements into whole numbers.
But presently renewed determinations of the atomic weights seemed
to discountenance this practice, and Prout's alleged law fell
into disrepute. It was revived, however, about 1840, by Dumas,
whose great authority secured it a respectful hearing, and whose
careful redetermination of the weight of carbon, making it
exactly twelve times that of hydrogen, aided the cause.

Subsequently Stas, the pupil of Dumas, undertook a long series of
determinations of atomic weights, with the expectation of
confirming the Proutian hypothesis. But his results seemed to
disprove the hypothesis, for the atomic weights of many elements
differed from whole numbers by more, it was thought, than the
limits of error of the experiments. It was noteworthy, however,
that the confidence of Dumas was not shaken, though he was led to
modify the hypothesis, and, in accordance with previous
suggestions of Clark and of Marignac, to recognize as the
primordial element, not hydrogen itself, but an atom half the
weight, or even one-fourth the weight, of that of hydrogen, of
which primordial atom the hydrogen atom itself is compounded. But
even in this modified form the hypothesis found great opposition
from experimental observers.

In 1864, however, a novel relation between the weights of the
elements and their other characteristics was called to the
attention of chemists by Professor John A. R. Newlands, of
London, who had noticed that if the elements are arranged