Dx = ε1Ex, Dy = ε2Ey, Dz = ε3Ez,
(14)
the constants ε1, ε2, ε3 (dielectric constants) depending on the properties of the body considered. In an isotropic medium they have a common value ε, which is equal to unity for the free aether, so that for this medium D = E.
(c) There is a relation similar to (14) between the magnetic force and the magnetic induction. For the aether, however, and for all ponderable bodies with which this article is concerned, we may write B = H.
It follows from these principles that, in an isotropic dielectric, transverse electric vibrations can be propagated with a velocity
v = c / √ε.
(15)
Indeed, all conditions are satisfied if we put
| Dx = 0, Dy = a cos n (t − xv−1 + l), | Dz = 0, |
| Hx = 0, Hy = 0, | Hz = avc−1 cos n (t − xv−1 + l) |
(16)