of work depending upon
the amount of energy that exists in the matter which is the vehicle of
energy.

In Art. 50 it has been indicated that the Aether possesses several kinds
of motions. From the sphere of light and heat, we learn that the Aether
possesses certain motions which are always exerted in a direction from
the central body, which gives rise to the light- and heat-waves. That
being so, it conclusively follows that the Aether possesses kinetic
energy, and therefore, possessing this energy, it also possesses the
power to do work. It must be remembered we are no longer dealing with a
frictionless medium, but with a gravitating medium, possessing mass and
inertia, and, that being so, wherever we have the Aether in motion,
there we have kinetic energy or the power to do work; and that work will
correspond to the particular kind of motion which is exerted on any body
by the aetherial motions, and will be equally subject to Newton's Laws
of Motion.

ART. 56. _Energy and Motion._--An advance, however, as to the meaning of
the term Energy has been made within recent years, which brings it more
into harmony with that simplicity of conception, and accordance with
experience which are the very foundation of all philosophy. Instead of
the term Energy, there is now being used another term to denote the
forces which form the life of the universe, and that term is the word
"Motion."

Professor Poynting says: "All energy is energy of motion" (_British
Association Report_, 1899).

Thus motion is the fundamental principle of all phenomena. If we analyze
all forms of energy with which we are familiar, we shall soon find that
they are only changes of one form of motion into another. Thus we shall
see that heat is a mode of motion, as has been proved by Tyndall, that
light is another mode of motion, and that electricity is also a mode of
motion. I need hardly point out that this advance in our conception of
energy is strictly in accord with the Rules of Philosophy. First, it is
simple in conception. When we say that a body possesses energy, whether
that energy be potential energy or kinetic energy, it does not convey to
the mind some definite concrete fact, as does the statement that a body
possesses motion. Every one, whether familiar with scientific teaching
or not, understands and is familiar with the word Motion, as it is a
common phenomenon of everyday life and experience. As Energy was simpler
in conception than Newton