must be sensibly uniform.  But, if the
molecules of the ether attracted each other, their
dispersion throughout space could not
continue uniform.  It is true that the exactly
uniform dispersion of an attractive fluid
would constitute a state of equilibrium; but
it would be an unstable equilibrium. That is
to say, if disturbed by the slightest local
condensation or refraction, the equilibrium
would be broken; the fluid would instantly
rush in masses to various centres, in virtue of
its attractive power, and the uniform
dispersion of the fluid would no longer exist.
There would ensue, immediately, in some
places, partial and local vacuums; and in
others, local and limited condensations of the
fluid.

On the other hand, a fluid whose particles
repelled each other, if distributed in a nearly
uniform manner in unlimited space, would
tend more and more to a uniform
distribution of its particles.  Any partial local
vacuum would be instantly filled up by the
adjoining particles rushing in.  In like
manner, any partial and local condensation
would determine a repulsion by which the
too crowded molecules would be driven away
from each other, till they met with an equal
repulsion from without.  Thus, the
uniform density of the celestial ether, which
remains sensibly the same in spite of the
local movements of the heavenly bodies,
shows that the atoms of the ether repel each
other.  And that the energy of the living
forces transmitted by the undulations of the
ether—the power of the solar light, heat, and
chemical action—proves that the repulsion of
its constituent atoms is enormous.

Bearing these facts in mind, is it possible
to conceive that the ether occupies a finite
space in a firmament which is geometrically
infinite in every direction?

If the extent of the ether is limited, it is
absolutely necessary that the space it occupies
should be enclosed in some vast,
continuous distended envelope, capable of
offering sufficient resistance to the ether's expansive
force, in spite of the enormous radius
and span which this sort of roof or vault
must have.  If, therefore, the ether be limited,
we are come back to the ancient dream of a
solid transparent firmament, made of crystal,
or of whatever other substance you please.  Be
it remembered that this firmament must
inclose, not only the sun and its planets, but
every star which we behold, and the Milky
Way of which they form part, and the nebulæ
amongst which our Milky Way is only a
single individual, and the congregations of
nebulae, and the congregations of those con-
gregations, and so on to infinity; there being
nothing to authorise our limiting the number
of the degrees of this stellar hierarchy.  Such
an idea as that of a crystal wall bounding
the universe, can hardly stand a moment's
reflection.

We are consequently led to conclude that
the celestial ether has no limits whatever;
but that it actually extends infinitely in
every direction of the geometrical heavens.
It now remains to inquire whether, in this
etherised immensity, the congregations of
stars can by possibility be assembled within
a limited space, beyond which there exists
nothing but the ether only, in all directions,
to infinity.

The totality of the stars which exist in
the celestial ether, continually transmit to it
an enormous quantity of vital force. This
force travels through the ether in calorific and
luminous undulations, and goes further and
further away, indefinitely, from the centres of
vibration, with nothing to stop it; unless the
undulations meet, on their way, with atoms
of a nature heterogeneous to the ether, which
retain, after the passage of a wave, some
fraction of the vital force of that wave.
Consequently, if all the ponderable matter of the
universe is confined within a given space, all
the light and all the heat which makes its
escape from this inclosure would be definitely
lost to the stellar universe, which would
therefore cool and grow dark to an indefinite
extent; and after a lapse of time, which,
though very great, is still finite, an epoch
would arrive when the sum of subsistent
vital force would fall below any appreciable
limit.  But if, on the contrary, the ponderable
universe is infinite, like the celestial ether,
in all directions, the whole of the vital force
propagated in the heavens remains always
within the circumference of this ponderable
universe.  In that case, the conservation of
action and of vital force becomes separately
applicable, on the one hand, to the totality of
the celestial ether; and, on the other hand, to
the totality of ponderable matter.  What is
given, and taken, is returned from every
opposite quarter, in equal measure; upon the
whole, there is no absolute loss or escape of
vital force.

Thus, a finite universe swimming in an
infinite ether must, little by little, lose its
living energies, without the possibility of
regaining them; an infinite universe, on the
contrary, must preserve its total vital force
under any changes whatever in its distribution,
such changes being produced partly
through the medium of the repulsive ether,
and partly by the action of universal
gravitation.  The latter of these two hypotheses
appears the only one admissible.  In fact, all
the manifestations of the creative power,
which are one in kind, appear, à priori, to be
necessarily inalterable in their sum, provided
we include in that sum the absolute totality
of creation.  This law, and that of continuity,
are perhaps the two laws which are the most
general throughout all creation; and the
notion of the indestructibility of matter, now
admitted as an axiom, rests upon no other
foundation.

An endeavour has therefore been made
to establish the proposition: First, that the