e must
look for the ultimate source of that repulsive power or Centrifugal
Force which is to form the complementary power to the attractive force
of Gravitation.

[Footnote 12: _Lectures on Scientific Subjects._]

ART. 65. _Direction of Ray of Heat._--The question as to the path which
a ray of heat takes may best be attacked by finding out what is the path
which a ray of light takes in its progress through the Aether. When we
come to deal with light, we shall find that it has been experimentally
proved that the path of a ray of light is that of a straight line
through space; so that if we have any body emitting light, the rays of
light will proceed from that body in straight lines, with decreasing
intensity, according to the law of inverse squares, the same as
Gravitation.

It can readily be shown, that wherever there is light there is heat. For
example, the radiant heat from the sun proceeds through space along with
the light from the sun, and when one set of waves, the light waves for
instance, are intercepted, the heat waves are also intercepted. Or, to
take another illustration, when the sun is eclipsed, we feel the sun's
heat as long as any portion of the sun is visible, but as soon as the
sun is totally eclipsed, then the light waves disappear, and with it the
heat waves. From this we can readily see, that not only do the heat and
light waves from the sun proceed in the same straight line, but that
they also travel at the same rate through space, at the rate of 186,000
miles per second. Then again the common lens, which is so familiar to
every one, will prove the same fact by concentrating the rays of light
to a focus, and by so doing will produce sufficient heat to burn a piece
of paper, or even set fire to wood. If, therefore, the path of a ray of
light be that of a straight line, proceeding from the luminous or
lighted body, and the path of a ray of heat coincides with the path of a
ray of light, the path of the ray of heat must also be in the direction
of a straight line from the heated or luminous body, which, as we shall
see in a subsequent article, also decreases in intensity according to
the law of inverse squares the same as Gravitation Attraction.

Professor Tyndall, on the direction of a ray of heat,[13] states his
opinion on the matter as follows: "A wave of Aether starting from a
radiant point in all directions in a uniform medium constitutes a
spherical shell, which expands with the velocity of