rm of motion. So
if one is to form a conception of the mechanical origin of electricity,
this is the only one he can have--transformed motion.

[Illustration: FIG. 6.--Thermo-pile.]

[Illustration: FIG. 7.--Dynamo.]

(2) When heat is the antecedent of electricity, as in the thermo-pile,
that which is turned into the pile we know to be molecular motion of a
definite kind. That which comes out of it must be some equivalent
motion, and if all that went in were transformed, then all that came out
would be transformed, call it by what name we will and let its amount be
what it may.

(3) When a conductor is moved in a magnetic field, the energy spent is
measurable in foot-pounds, as before, a pressure into a distance. The
energy appears in a new form, but the quantity of matter being
unchanged, the only changeable factor is the kind of motion, and that
the motion is molecular is evident, for the molecules are heated.
Mechanical or mass motion is the antecedent, molecular heat motion is
the consequent, and the way we know there has been some intermediate
form is, that heat is not conducted at the rate which is observed in
such a case. Call it by what name one will, some form of motion has been
intermediate between the antecedent and the consequent, else we have
some other factor of energy to reckon with than ether, matter and
motion.

(4) In a galvanic battery, the source of electricity is chemical action;
but what is chemical action? Simply an exchange of the constituents of
molecules--a change which involves exchange of energy. Molecules capable
of doing chemical work are loaded with energy. The chemical products of
battery action are molecules of different constitution, with smaller
amounts of energy as measured in calorics or heat units. If the results
of the chemical reaction be prevented from escaping, by confining them
to the cell itself, the whole energy appears as heat and raises the
temperature of the cell. If a so-called circuit be provided, the energy
is distributed through it, and less heat is spent in the cell, but
whether it be in one place or another, the mass of matter involved is
not changed, and the variable factor is the motion, the same as in the
other cases. The mechanical conceptions appropriate are the
transformation of one kind of motion into another kind by the mechanical
conditions provided.

[Illustration: FIG. 8.--Galvanic Battery.]

(5) Physiological antecedents of electricity are exempli