matter,
as elasticity, density and inertia, it is not subject to the very
property which of all properties is the most fundamental, viz.
Gravitation. There can, in my opinion, only be one answer to the
question, so that, when we affirm that Aether is matter, we are
compelled to affirm, in order to conform to the first Rule of
Philosophy, that it is gravitative also. Faraday was also of the opinion
that Aether was subject to the Law of Gravity, for, writing in
_Experimental Researches_, he states: "The view now stated of the
constitution of matter, would seem to involve the conclusion, that
matter fills all space, or at least all space to which Gravitation
extends, INCLUDING THE SUN AND ITS SYSTEM. For Gravitation is a property
of matter, dependable on a certain force, and it is this force which
constitutes matter."

Let us also test the question by our second Rule of Philosophy, and we
shall find greater evidence still for the statement that Aether is
gravitative. What do experience and observation teach us with reference
to matter? As we have already seen (Art. 37), if there is one truth that
they teach us regarding matter, it is that it is gravitative.

There is not the slightest evidence throughout the universe, as far as
our observation can lead us to form an opinion, that there is any kind
of matter which is not subject to the Law of Gravitation. Therefore to
assume that Aether is matter, and yet not to assume that it is also
subject to Gravitation, is to assume that which is directly opposed to
the most fundamental principle of all philosophical teaching and
scientific research. If Aether be matter, therefore, and yet is not
gravitative, we shall have an anomaly in an otherwise universal law, as
we shall have some kind of matter which fails to come within the scope
of the universal Law of Gravitation.

To be consistent, therefore, we must either cease to call Aether matter,
or else admit that Aether, like all other matter, is gravitative. It is
absolutely impossible to be strictly logical and admit that Aether is
matter, and not to admit that it is subject to the most universal law
that governs matter, as the Law of Gravitation distinctly states that
"every particle or atom of matter attracts every other particle." This
universal law in view of a gravitationless Aether would have to be
amended to "Some particles of matter attract some other particles." Thus
the universal Law of Gravitation ceases at once to be