and further

(48) | , |

Because *F* is an alternating matrix,

(49) | , |

*i.e.* is perpendicular to the vector to *w*; we can also write

(50) | , |

I shall call the space-time vector of the first kind as the *Electric Rest Force*.

Relations analogous to those holding between , hold amongst , and in particular *-wf* is normal to *w*. The relation (C) can be written as

{C} |

The expression (*wf*) gives four components, but the fourth can be derived from the first three.

Let us now form the time-space vector 1st kind , whose components are

Of these, the first three are the *x-, y-, z-*components of the space-vector

(51) | , |

and further

(52) | ; |

Among these there is the relation

(53) | , |

which can also be written as