(54) |

The vector is perpendicular to *w*; we can call it the *Magnetic rest-force*.

Relations analogous to these hold among the quantities and Relation (D) can be replaced by the formula

{D} |

We can use the relations (C) and (D) to calculate *F* and *f* from and , we have

and applying the relation (45) and (46), we have

(55) | , |

(56) | , |

*i.e.*

, etc.
, etc. |

Let us now consider the space-time vector of the second kind , with the components

,
, |

Then the corresponding space-time vector of the first kind

vanishes identically owing to equations 49) and 53).

Let us now take the vector of the 1st kind

(57) |

with the components

Then by applying rule (45), we have