1. Maxwell. Treatise, 2nd edition Vol. i, 29–29. That for electricity also there are minimal quantities which can be no longer divided, and which are associated with the smallest particles of ponderable masses, may be differently expressed. Letebe this elementary quantity, and X, Y, and Z the components of the forces exerted by it, thene=-1/4φ(∂X/∂x+∂Y/∂y+∂Z/∂z). The expression within the brackets is, however, nothing more than the “convergence of electrical lines of force”§25, compare also Heaviside, Electrical Papers, i. p. 210, 1892). So that we may also say, the convergence of electrical rays of force towards an atom of ponderable matter cannot sink below a certain limit. According to this the existence of electrical elementary quantities is closely connected with thegeometricalproperties of our space and its being filled with matter. By resting on definite mechanical representations further reasons may be adduced: thus, for instance, tubes of force are identified with vortex threads of the æther, as in some mechanical theories of the electrical field. Such threads can return to themselves, or may end in the corporeal atoms in the æther. But as they must have a definite cross section, only a limited number can terminate on a smallest corporeal particle
2. v. Helmholtz , H. 1884. Vorträge und Reden Vol. ii, 317–317.
3. 1883. Wiener Berichte 861–861.
4. Electrische Schwingungen molecularer Gebilde