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 requires an entrainment of electricity by ions, then a persistent electric current never consists of a convection alone, at least not when the centers of two touching or interconnected particles are in some distance $$l$$ from each other. Then the electricity motion happens without convection over a distance of order $$l$$, and only if this is very small in proportion to the distance over which a convection takes place, we on the whole are dealing almost exclusively with this latter phenomenon.

is of the opinion that in metals a real convection was not at all in play. But since it does not seem possible to include the "jumping" of the charges into the theory, then one would excuse, that for my part I totally disregard such a process, and that I interpret a current in a metal wire simply as a motion of charged particles.

Further research will have to decide whether the results of the theory remains at a different view.

§ 3. The theory of ions was very suitable for my purpose, because it makes it possible to introduce the permeability of the aether in a rather satisfactory way in the equations. Of course, these were decomposed into two groups. First, we have to express as to how the state of the aether by charge, position and motion of the ions is determined; then, secondly, we have to indicate by which forces the aether is acting on the charged particles. In my paper already cited I have derived the formulas by means of 's principle from certain assumptions and therefore selected a path, that has much resemblance with 's application of 's equations. Now I prefer for the sake of brevity, to introduce the basic equations themselves as hypotheses.

The formulas for the aether are in agreement, regarding the space between