ered as separate.

Among all the theories lately proposed, that of the ions has taken a
preponderant place; ill understood at first by some, appearing
somewhat singular, and in any case useless, to others, it met at its
inception, in France at least, with only very moderate favour.

To-day things have greatly changed, and those even who ignored it have
been seduced by the curious way in which it adapts itself to the
interpretation of the most recent experiments on very different
subjects. A very natural reaction has set in; and I might almost say
that a question of fashion has led to some exaggerations.

The electron has conquered physics, and many adore the new idol rather
blindly. Certainly we can only bow before an hypothesis which enables
us to group in the same synthesis all the discoveries on electric
discharges and on radioactive substances, and which leads to a
satisfactory theory of optics and of electricity; while by the
intermediary of radiating heat it seems likely to embrace shortly the
principles of thermodynamics also. Certainly one must admire the power
of a creed which penetrates also into the domain of mechanics and
furnishes a simple representation of the essential properties of
matter; but it is right not to lose sight of the fact that an image
may be a well-founded appearance, but may not be capable of being
exactly superposed on the objective reality.

The conception of the atom of electricity, the foundation of the
material atoms, evidently enables us to penetrate further into
Nature's secrets than our predecessors; but we must not be satisfied
with words, and the mystery is not solved when, by a legitimate
artifice, the difficulty has simply been thrust further back. We have
transferred to an element ever smaller and smaller those physical
qualities which in antiquity were attributed to the whole of a
substance; and then we shifted them later to those chemical atoms
which, united together, constitute this whole. To-day we pass them on
to the electrons which compose these atoms. The indivisible is thus
rendered, in a way, smaller and smaller, but we are still unacquainted
with what its substance may be. The notion of an electric charge which
we substitute for that of a material mass will permit phenomena to be
united which we thought separate, but it cannot be considered a
definite explanation, or as the term at which science must stop. It is
probable, however, that for a few years still physi