Ther is called into play. After the jar is discharged, however, the recoil of the Aether produces a current, and the inertia of the current causes it to overshoot its original position, and for an instant the charge of the jar is reversed. The current now flows backwards in the same way that the lath returned back, and charges the jar as at first. This discharging and recharging continue backward and forward, so to speak, until all the energy which was originally given to the jar has been expended, and it resumes its normal condition. In this experiment the elasticity and inertia of the Aether have both been called into play, so that we see in this electrical experiment a similar illustration of the elasticity and inertia of the Aether, as manifested in the undulatory or wave theory of light. The question now arises, what are the corresponding properties as given by Maxwell in his electro-magnetic theory? In Art. 782 he writes: "In the theory of electricity and magnetism adopted in this treatise two forms of energy are recognized--the electro-static and the electro-kinetic--and these are supposed to have their seat, not merely in the electrified or magnetized bodies, but in every part of the surrounding space where electric or magnetic force is observed to act. Hence our theory agrees