The locus of event-particles covered by the station of P in d as an abstractive element is the station of P in d as a locus.

A station has accordingly the usual three characters, namely, its character of position, its extrinsic character as an abstractive element, and its intrinsic character.
It follows from the peculiar properties of rest that two stations belonging to the same duration cannot intersect.

Accordingly every event-particle on a station of a duration has that station as its station in the duration.

Also every duration which is part of a given duration intersects the stations of the given duration in loci which are its own stations.

By means of these properties we can utilise the overlappings of the durations of one family--that is, of one time-system--to prolong stations indefinitely backwards and forwards.
Such a prolonged station will be called a point-track.