*i.e.* the components of the convection current , and the electric density multiplied by .

Further I shall write

for

i.e., the components of and along the three axes; now if we take any two indices *h, k* out of the series

therefore

,
, |

Then the three equations comprised in (I), and the equation (II) multiplied by *i* becomes

(A) |

On the other hand, the three equations comprised in (III) multiplied by *-i*, and equation (IV) multiplied by -1, become

(B) |

By means of this method of writing we at once notice the *perfect symmetry* of the 1st as well as the 2nd system of equations