or
planets away into the depths of space, never to return to their central
sun.

If there were no Centrifugal Force, then the Centripetal Force would
draw all bodies, _i. e._ all planets, etc., to their central sun, and,
instead of the planets continually revolving round the sun, there would
be but one immense solitary mass in the centre of the solar system.

If there were no Laws of Motion, with their necessary corollary the
Parallelogram of Forces, the Primitive Impulse would cease to act, and
the Law of Gravitation would again fail in its attempt to account for
those phenomena it does account for.

Thus, as it may easily be seen, Gravitation is a compound Law, depending
upon at least four hypotheses, and therefore is not essentially a simple
Force, or Law.

If, therefore, in giving a physical explanation of the cause of
Gravitation, we can reduce all these four elements of the Law into one
single physical cause, _i. e._ the Universal Aether, and show how they
may all be explained and accounted for by the properties, qualities and
motions of that physical medium, then such a result will be strictly in
harmony with the first Rule of Philosophy, as laid down by Newton and
others.

We will, therefore, proceed to consider some of these parts of the Law
of Gravitation in detail.

ART. 9. _Primitive Impulse._--This may be explained as follows. At the
creating and launching of each world, Newton supposed that there was
given to each world an impulse or tendency to fly off from the
controlling centre into space. On this matter MacLaurin writes as
follows: "If we had engines of sufficient force, bodies might be
projected from them, so as not only to be carried a vast distance away
without falling to the earth, but so as to move round the whole earth
without touching it; and, after returning to the first place, commence a
new revolution with the same force they first received from the engine;
and after the second revolution, a third, and thus revolve as a moon or
satellite round the earth for ever. If this can be effected near the
earth's surface, it may be done higher in the air, or even as high as
the moon. By increasing the force or power, a body proportionately
larger may be thus projected, and by a power sufficiently great, a heavy
body, not inferior to the moon, might be put in motion, which might
revolve for ever round the earth. Thus Sir Isaac Newton saw that the
curvilineal motion of the moon in her orbit, an