ding to
that law throughout all nature, it is evident that as the earth is sixty
semi-diameters distant from the moon, a heavy body must necessarily fall
(on the earth) fifteen feet in the first second, and fifty-four thousand
feet in the first minute.

Now a heavy body falls, in reality, fifteen feet in the first second, and
goes in the first minute fifty-four thousand feet, which number is the
square of sixty multiplied by fifteen. Bodies, therefore, gravitate in
an inverse ratio of the squares of the distances; consequently, what
causes gravity on earth, and keeps the moon in its orbit, is one and the
same power; it being demonstrated that the moon gravitates on the earth,
which is the centre of its particular motion, it is demonstrated that the
earth and the moon gravitate on the sun which is the centre of their
annual motion.

The rest of the planets must be subject to this general law; and if this
law exists, these planets must follow the laws which Kepler discovered.
All these laws, all these relations are indeed observed by the planets
with the utmost exactness; therefore, the power of attraction causes all
the planets to gravitate towards the sun, in like manner as the moon
gravitates towards our globe.

Finally, as in all bodies re-action is equal to action, it is certain
that the earth gravitates also towards the moon; and that the sun
gravitates towards both. That every one of the satellites of Saturn
gravitates towards the other four, and the other four towards it; all
five towards Saturn, and Saturn towards all. That it is the same with
regard to Jupiter; and that all these globes are attracted by the sun,
which is reciprocally attracted by them.

This power of gravitation acts proportionably to the quantity of matter
in bodies, a truth which Sir Isaac has demonstrated by experiments. This
new discovery has been of use to show that the sun (the centre of the
planetary system) attracts them all in a direct ratio of their quantity
of matter combined with their nearness. From hence Sir Isaac, rising by
degrees to discoveries which seemed not to be formed for the human mind,
is bold enough to compute the quantity of matter contained in the sun and
in every planet; and in this manner shows, from the simple laws of
mechanics, that every celestial globe ought necessarily to be where it is
placed.

His bare principle of the laws of gravitation accounts for all the
apparent inequalities in the course of