cording to the first law of motion, the
planet would remain in a state of rest until compelled by other forces
or motions to change that state, when it would continue moving with
uniform motion so long as the motive power applied was uniform.

If, however, the motive power applied was not uniform, then the result
would be an increase or decrease of the planet's motion, just in
proportion to the increase or decrease of the motive power. This result
is in perfect harmony with our statement in Art. 15, and is in
accordance with observation and experience.

ART. 99. _Second Law of Motion._--According to Newton's Second Law of
Motion, "Change of motion is proportional to the impressed force, and
takes place in the direction in which the force is impressed."

From a consideration of this Law (Art. 15) we saw that the impressed
force was a compound quantity, being regulated by the mass of the moving
body which exerted the impressed force, and that it was also
proportionate to the velocity of the moving body; so that if either of
these quantities are changed, the total impressed force would be changed
also.

We have now to show that our aetherial medium agrees with this second
law of motion in so far as the second law of motion agrees with
experience and experiments. To do this, we must review our conception of
the universal Aether, and remember that Aether is matter, and being
matter, it is atomic and gravitative, possessing density, elasticity,
inertia, and kinetic energy, the same as any other moving matter.

In this Aether medium we have, according to this conception, something
that can both push and pull, or exert force upon any body with which it
comes into contact. Further, the inertia and kinetic energy of the
Aether at any part of space will be regulated by its mass in that
particular part, and if its mass is denser in some parts than others,
that part of the aetherial medium possessing the greatest mass will also
possess the greatest capacity for impressing force upon any body that
exists in the medium. Now we have learned from Art. 45 that Aether being
gravitative, it is denser nearer to the sun, getting gradually less and
less dense, the further it recedes from the central body, except where
it is bound or associated to some other planet or satellite, and there
it gradually gets denser, for the same reason that it is denser nearer
to the sun. As, therefore, the Aether gets gradually less dense as it
recedes f