propriate form is the
condition of its taking place. If heat appears, then its antecedent has
been some other form of motion acting upon the substance heated. It may
have been the mechanical motion of another mass of matter, as when a
bullet strikes a target and becomes heated; or it may be friction, as
when a car-axle heats when run without proper oiling to reduce friction;
or it may be condensation, as when tinder is ignited by condensing the
air about it; or chemical reactions, when molecular structure is changed
as in combustion, or an electrical current, which implies a dynamo and
steam-engine or water-power. If light appears, its antecedent has been
impact or friction, condensation or chemical action, and if electricity
appears the same sort of antecedents are present. Whether the one or the
other of these forms of energy is developed, depends upon what kind of a
structure the antecedent energy has acted upon. If radiant energy,
so-called, falls upon a mass of matter, what is absorbed is at once
transformed into heat or into electric or magnetic effects; _which_ one
of these depends upon the character of the mechanism upon which the
radiant energy acts, but the radiant energy itself, which consists of
ether-waves, is traceable back in every case to a mass of matter having
definite characteristic motions.

One may therefore say with certainty that every physical phenomenon is a
change in the direction, or velocity, or character, of the energy
present, and such change has been produced by matter acting as a
transformer.

THE ETHER IS A NON-TRANSFORMER.

It has already been said that the absence of friction in the ether
enables light-waves to maintain their identity for an indefinite time,
and to an indefinitely great distance. In a uniform, homogeneous
substance of any kind, any kind of energy which might be in it would
continue in it without any change. Uniformity and homogeneity imply
similarity throughout, and the necessary condition for transformation is
unlikeness. One might not look for any kind of physical phenomenon which
was not due to the presence and activity of some heterogeneity.

As a ray of light continues a ray of light so long as it exists in free
ether, so all kinds of radiations, of whatever wave-length, continue
identical until they fall upon some mechanical structure called matter.
Translatory motion continues translatory, rotary continues rotary, and
vibratory continues to be vibratory, a