lly the centre of a
power whose influence and motion are exerted along exactly the same path
as the centripetal force, but in an opposite direction, that is, away
from the sun. I hope to be able to show that the aetherial light waves
do possess such a dynamical value, and if that is accomplished, then not
only from the realm of heat, but also from the realm of light, we shall
have conclusive evidence of a power or motion whose influence is
directed away from the sun, which, therefore, would correspond to a
centrifugal force--that is, a force or motion directed from a central
body as the sun.

ART. 75. _Intensity of Light._--The intensity of light diminishes with
the distance from the luminous body, according to the same law that
governs sound, and heat, and electricity. We have already seen (Art. 67)
that the intensity of heat diminishes inversely as the square of the
distance, so that if the same law holds good for light that holds good
for heat, then, according to the law of the inverse squares, if we
double the distance from the luminous body, the intensity of light is
only 1/4 of what it was in its first position. If the distance be
trebled, then the intensity will be decreased 1/9. This can easily be
proved by the following experiment: Suppose we have a lighted lamp, and
at a distance of 1, 2 and 3 feet respectively, we have three square
surfaces. It can then be demonstrated that the light which falls on the
square 1 foot away, if allowed to fall upon the square 2 feet away,
would cover four times the area of the first square; and if allowed to
fall on the square 3 feet away, it would cover nine times the area.
Therefore the intensity of the light on the square 2 feet away, covering
four times the area, would only be 1/4 of what it is on the square 1
foot away, while the intensity of light on the square 3 feet away, which
covers nine times the area, would only be 1/9 of the intensity received
by the first square.

If the difference in the distances therefore be represented by the
figures 1, 2, and 3 feet respectively, the intensity would be
represented by the figures 1, 1/4, 1/9. The decrease in the intensity of
light is really a decrease in motion. The intensity of a note in sound
depends upon the vibration of the particles of air, while the intensity
of light also depends upon the vibrations of the aetherial atom.

If, therefore, we get a decrease in the vibration of the aetherial atom,
the further we get fr