We have ρ₀φ₁ = ρ[_d__{_x_} + 1/_c_ (_v₂_ _h₃_ - _v₃_ _h₂_)]

N. B.—We have put the components of _e_ equivalent to (_d__{_x_},

_d__{_y_}, _d__{_z_}), and the components of _m_ equivalent to _h__{_x_}

_h__{_y_} _h__{_z_}), in accordance with the notation used in Lorentz’s

Theory of Electrons.