er, but the proportion of the
attractive forces between the two bodies, is about 324,000 to 1. This
difference is accounted for by the fact, that the density of the sun is
about one quarter the mean density of the earth, hence their masses are
in the proportion of 324,000 to 1. Thus the proportion of the attractive
forces between any two bodies is dependent upon their masses, and not
simply upon their volume or density.

ART. 22. _Law of Inverse Squares._--The Law of Inverse Squares which is
applicable to Gravitation is equally true of Sound, Light, Heat and
Electricity, the Law being that Gravitation acts inversely as the square
of distance. That is to say, if the distance of any body from the sun,
for example, be doubled, then the force of Gravitation is diminished to
one quarter of the intensity which would be exerted on the body in the
first position.

Thus the further a body is from its controlling centre, the weaker the
Attraction of Gravitation upon it becomes. Taking therefore Mercury and
the earth as examples, we find that their mean distances are
respectively 35,000,000 miles and 92,000,000, which is a proportion of
about 1 to 2-1/2. So that the intensity of the sun's attraction on the
earth is about four-twenty-fifths of what it is on Mercury, that being
the inverse square of the relative distances of the two bodies.

Now the intensity of Light and Heat received by the earth is regulated
by the same law of inverse squares, so that the earth would receive
about four-twenty-fifths the intensity of light and heat which Mercury
receives when they are both at their mean distances.

This law of inverse squares is applicable to every body which acts as a
gravitating source throughout the whole of the universe, whether that
body be small or large, and whether it be in the form of meteor,
satellite, planet, sun or star.

Each satellite, planet or sun exerts an attractive influence upon every
body that exists, that attractive influence being regulated by the
masses of the respective bodies, and decreasing inversely as the square
of the distance from the body viewed as the centre of attraction. So
that, the further the attracted body is from the attracting body, the
less is the intensity of the mutual attracting forces, though that
intensity does not vary simply as the distance, but rather as the square
of the distance, and that in its inverse ratio. Thus if we take two
masses of any kind or sort, and place them