[1] He compares the interpenetration of two atoms to the
coalescence of two distinct waves, which though for a moment blended
to a single mass, preserve their individuality, and afterwards
separate.

[2] In this form the experiment is identical with one made twenty
years earlier. See page 34.


Chapter 14.

Unity and convertibility of natural forces:
theory of the electric current.

The terms unity and convertibility, as applied to natural forces,
are often employed in these investigations, many profound and
beautiful thoughts respecting these subjects being expressed in
Faraday's memoirs. Modern inquiry has, however, much augmented our
knowledge of the relationship of natural forces, and it seems worth
while to say a few words here, tending to clear up certain
misconceptions which appear to exist among philosophic writers
regarding this relationship.

The whole stock of energy or working-power in the world consists of
attractions, repulsions, and motions. If the attractions and
repulsions are so circumstanced as to be able to produce motion,
they are sources of working-power, but not otherwise. Let us for
the sake of simplicity confine our attention to the case of
attraction. The attraction exerted between the earth and a body at