{ ∂F₁₂/∂x₃ + ∂F₂₃/∂x₁ ∂F₃₁/∂x₂ = 0.
This system of equations corresponds to the second system of equations of Maxwell. We see it at once if we put
{ F₂₃ = Hx F₁₄ = Ex
{
(61) { F₃₁ = Hy F₂₄ = Ey
{
{ F₁₂ = Hz F₃₄ = Ez
Instead of (60a) we can therefore write according to the usual notation of three-dimensional vector-analysis:—
{ ∂H/∂t + rot E = 0
(60b) {