distance between them. Let A and B be the bodies, and suppose that parabolic wires without mass are fixed to them, if these are threaded through a ring P with a small but finite mass and the system caused to rotate round A and B, the effort of the ring to get away from the axis of rotation will cause A and B to approach each other, and the law of approach may easily be shown to be the same as if there was a force between them varying inversely as the square of the distance.

The result mentioned on page 10 that the potential energy of a system charged with electricity is equal to the kinetic energy of the mass of ether bound to the system when moving with the velocity of light is another example of potential energy, being in reality the kinetic energy of an associated system, and indeed, as I have endeavoured to bring before you this evening, the study of the problems brought before us by recent investigations leads us to the conclusion that ordinary material systems must be connected with invisible systems which possess mass whenever the material systems contain electrical charges. If we regard all matter as satisfying this condition we are led to the conclusion that the invisible universe—the ether—is to a large extent the workshop of the material universe, and that the phenomena of nature as we see them are fabrics woven in the looms of this unseen universe.