has been explained as molecular or atomic phenomena, and there
is one more in that category which is well enough known, and which is so
important and suggestive, that the wonder is its significance has not
been seen by those who have sought to interpret electrical phenomena.
The reference is to the fact that electricity cannot be transmitted
through a vacuum. An electric arc begins to spread out as the density of
the air decreases, and presently it is extinguished. An induction spark
that will jump two or three feet in air cannot be made to bridge the
tenth of an inch in an ordinary vacuum. A vacuum is a perfect
non-conductor of electricity. Is there more than one possible
interpretation to this, namely, that electricity is fundamentally a
molecular and atomic phenomenon, and in the absence of molecules cannot
exist? One may say, "Electrical _action_ is not hindered by a vacuum,"
which is true, but has quite another interpretation than the implication
that electricity is an ether phenomenon. The heat of the sun in some way
gets to the earth, but what takes place in the ether is not
heat-transmission. There is no heat in space, and no one is at liberty
to say, or think, that there can be heat in the absence of matter.

When heat has been transformed into ether waves, it is no longer heat,
call it by what name one will. Formerly, such waves were called
heat-waves; no one, properly informed, does so now. In like manner, if
electrical motions or conditions in matter be transformed, no matter
how, it is no longer proper to speak of such transformed motions or
conditions as electricity. Thus, if electrical energy be transformed
into heat, no one thinks of speaking of the latter as electrical. If the
electrical energy be transformed into mechanical of any sort, no one
thinks of calling the latter electrical because of its antecedent. If
electrical motions be transformed into ether actions of any kind, why
should we continue to speak of the transformed motions or energy as
being electrical? Electricity may be the antecedent, in the same sense
as the mechanical motion of a bullet may be the antecedent of the heat
developed when the latter strikes the target; and if it be granted that
a vacuum is a perfect non-conductor of electricity, then it is
manifestly improper to speak of any phenomenon in the ether as an
electrical phenomenon. It is from the failure to make this distinction
that most of the trouble has come in thinking on