d not one; that is, if we are to accept the results of
up-to-date experiments in relation to radiant light and heat as
performed by Professor Lebedew, and Nichols and Hull of America. Their
experiments conclusively prove that light waves exert a pressure upon
all bodies on which they fall, and by no reasoning can this pressure be
resolved into an attractive force.

Herschel in his _Lectures on Scientific Subjects_ definitely refers to
the existence of a repulsive force in the solar system, and asserts that
it offers the most interesting prospect of any future discovery.

The author has therefore attacked the problem of the cause of
gravitation, by trying to solve the problem of the cause of the
_repulsive_ force which has been experimentally demonstrated to exist by
Professor Lebedew and others.

In his efforts to ascertain the physical cause of the Centrifugal Force,
he has been assisted by an unknown and original essay written by an
unknown writer over twenty years ago. That unknown writer was the
author's father, who wrote an essay on the _Complementary Law of
Gravitation_, and if it had not been for that essay, the present work
would never have been attempted.

The main object of the author in Chapters VI., VII., and VIII., is to
prove beyond the possibility of contradiction, from the phenomena of
heat, light, and electricity, the existence of _two_ forces in the solar
system; and by so doing, to bring our philosophy of the aether medium,
and all gravitational phenomena, into harmony with all observation and
experiments, which at present is not the case. In seeking to do this he
found that the new theory of the aether harmonized with views given, by
Faraday and Clerk Maxwell in relation to electric and magnetic
phenomena, and by the new theory Maxwell's hypothesis of "Physical Lines
of Force" receives a definite and physical basis. In Chapter X. the
author endeavours to show what the Electro-Kinetic energy is, which term
is used by Clerk Maxwell, the term being brought for the first time into
harmony with our experience. The Electro-Magnetic Theory of Light also
receives fresh light from the new theory of an atomic and gravitating
aether.

In the succeeding chapters the theory is applied to Newton's Laws of
Motion and Kepler's Laws, and is found to harmonize with all the results
given by these laws. Such a result is a distinct advance on the
application of a frictionless aether to solar and stellar phenomena, a