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Experiments whose results cannot be explained without further ado.

The rotation of the polarization plane.

§ 84. As the equations of motion of light for an isotropic body that has not the same properties as its mirror image, we have to assume by the considerations of the 4th section:

$Div\ {\mathfrak {D}}=0$,

$(I_{e})$

$Div\ {\mathfrak {H}}=0$,

$(II_{e})$

$Rot\ {\mathfrak {H}}'=4\pi {\dot {\mathfrak {D}}}$,

$(III_{e})$

$Rot\ {\mathfrak {E}}=-{\dot {\mathfrak {H}}}$,

$(IV_{e})$

${\mathfrak {E}}=4\pi V^{2}{\mathfrak {d}}+[{\mathfrak {p.H}}]$,

$(V_{e})$

${\mathfrak {H}}'={\mathfrak {H}}-4\pi [{\mathfrak {p.d}}]$,

$(VI_{e})$

${\mathfrak {D}}={\mathfrak {d}}+{\mathfrak {M}}$,

(X)

${\mathfrak {E}}=\sigma {\mathfrak {M}}+j\ Rot\ {\mathfrak {M}}+k[{\mathfrak {{\dot {M.}}p}}]$,

(XI)

where by ${\mathfrak {E,d,H}}$ and ${\mathfrak {H}}'$ we have to understand averages.

We now want to presuppose, that the velocity ${\mathfrak {p}}$ would have the direction of the x-axis, and to study the propagation of plane waves, whose normal coincides with that axis as well.

§ 85. To find a particular solution of the equations corresponding to such waves, we put

${\mathfrak {H}}_{x}=0,\ {\mathfrak {H}}_{y}=ae^{nt-mx},\ {\mathfrak {H}}_{z}=\nu \ {\mathfrak {H}}_{y}$

where a, ν, n and m are constants. Already by that, the condition ($II_{e}$) is satisfied.