in regard
to the mechanical energy of Light, states that "the amount of energy
poured forth into space corresponds in round numbers to 12,000
horse-power per square foot," and that every square foot of the sun's
surface supplies energy at the above rate. The number of feet in the
sun's surface can be approximately determined. Roughly, there are
2,284,000,000 square miles of surface on the sun's huge form, and there
are 27,878,400 square feet in a mile. By multiplying these two numbers
we can ascertain the exact number of square feet on the surface of the
sun. If, therefore, every square foot possesses a mechanical value equal
to 12,000 horse-power, what must be the mechanical equivalent of the
sun's radiation of light that it pours forth into space?

I want to call the attention of the reader to another fact, and that is,
that light always proceeds in straight lines from the sun (Art. 76), and
therefore if there be any mechanical action in light at all, that action
must be one which is always directed from the sun in straight lines. Now
experience universally teaches us, that if a body is pushed, and pushed
with such a force as has been indicated, then that body not only moves,
but moves in the direction that the supposed horses would push. I have
already shown (Art. 76) that the path of light is that of a straight
line corresponding to the path of the attractive force of gravity;
therefore these horses must ever push in a direction _from_ the sun
along the same path that the sun's attractive power takes. In other
words, the mechanical action of these supposed horses will be a
repulsive one, that repulsion being due to the dynamical action of the
light waves upon the body that they come into contact with. If this is
correct, then not only is heat a repulsive motion, as stated in Art. 63,
but light is equally the possessor of a repulsive motion, because its
action is ever directed from the sun. We might continue to follow the
supposed horses as they continued their course through space, and we
should find that their energy decreased inversely as the square of the
distance, partly because the further they proceeded into space the
larger the area would be they would have to cover, and therefore their
energy would be decreased proportionately.

Professor Stokes, in the same work[19] already referred to, in
continuation of the same idea, states: "At the distance of the earth the
energy received would correspond to about one