rever we get motion of any
kind or sort, there we have the capacity or power to do work. The work
done may be either in the form of pushing a body along, or pulling a
body towards a centre. All experience and observation teach us that no
body moves (whether it be an atom, or moon, or planet, or sun, or star),
unless some other body or medium, which is in direct contact with the
moving body, exercises some pressure or pull upon the moving body. The
action is purely and simply a mechanical one. So that if this be true,
then the earth and the planets, the sun and stars, comets and meteors,
are moved through space solely because they are being pushed by some
medium, or pulled to the centre by the motions of the same medium. If
this can be proved to be true, then, as can be readily seen, our
philosophy will then be made to agree with our experience, and the
second Rule of Philosophy fully satisfied. As has already been pointed
out, there is no such thing as action at a distance, therefore the Law
of Gravitation demands a medium for its operation, production, and
continuity. Newton distinctly points this out in his Letters to Bentley,
where he says: "That one body should act upon another through empty
space without the mediation of anything else, by and through which their
action and pressure may be conveyed from one to another, is to me so
great an absurdity that I believe no man who has in philosophical
matters a faculty for thinking can ever fall into it." It has already
been pointed out (Art. 42), that the only medium which is universal is
the Aether medium, and we have therefore to look to the motions and
properties of that medium for the solution of the problem as to the
physical cause of Gravitation. That such a medium has motions which are
as regular as the tides of the sea, or the trade winds of the
atmosphere, will be proved later on, when it will be found that
Gravitation, with all that that law implies, is due, as Newton and
Challis suggested, to the pressure, properties, and motions of the
aetherial medium, which is as universal as Gravitation itself. This
being so, it is essential that we should set ourselves to find out from
the analogies of Nature, what are those properties and motions of the
Aether which give rise to the universal Law of Gravitation. This I
propose doing by a consideration of three different modes of
motion--viz. Heat, a mode of motion; Light, a mode of motion; and
Electricity, a mode of motio