l matter to a single element; it contains, it may be, not merely a
germ of the science of the nineteenth-century chemistry, but perhaps the
germs also of the yet undeveloped chemistry of the twentieth century.
Yet we dare suggest that in their enthusiasm for the atomic theory of
Democritus the historians of our generation have done something less
than justice to that philosopher's precursor, Anaxagoras. And one
suspects that the mere accident of a name has been instrumental in
producing this result. Democritus called his primordial element an atom;
Anaxagoras, too, conceived a primordial element, but he called it merely
a seed or thing; he failed to christen it distinctively. Modern science
adopted the word atom and gave it universal vogue. It owed a debt of
gratitude to Democritus for supplying it the word, but it somewhat
overpaid the debt in too closely linking the new meaning of the word
with its old original one. For, let it be clearly understood, the
Daltonian atom is not precisely comparable with the atom of Democritus.
The atom, as Democritus conceived it, was monistic; all atoms, according
to this hypothesis, are of the same substance; one atom differs from
another merely in size and shape, but not at all in quality. But the
Daltonian hypothesis conceived, and nearly all the experimental efforts
of the nineteenth century seemed to prove, that there are numerous
classes of atoms, each differing in its very essence from the others.

As the case stands to-day the chemist deals with seventy-odd substances,
which he calls elements. Each one of these substances is, as he
conceives it, made up of elementary atoms having a unique personality,
each differing in quality from all the others. As far as experiment has
thus far safely carried us, the atom of gold is a primordial element
which remains an atom of gold and nothing else, no matter with what
other atoms it is associated. So, too, of the atom of silver, or zinc,
or sodium--in short, of each and every one of the seventy-odd elements.
There are, indeed, as we shall see, experiments that suggest the
dissolution of the atom--that suggest, in short, that the Daltonian atom
is misnamed, being a structure that may, under certain conditions, be
broken asunder. But these experiments have, as yet, the warrant rather
of philosophy than of pure science, and to-day we demand that the
philosophy of science shall be the handmaid of experiment.

When experiment shall have demonst