′. In this way the station
is prolonged in the time-system by the addition of the station
, and so on indefinitely. The complete locus of event-particles thus defined by the indefinite prolongation of a station throughout its associated time-system is called a 'point-track.'
A point-track intersects any moment of any time-system in one and only one event-particle.
42.3 Each point-track has a unique association with the time-system in which the routes lying on it are stations. A point-track is called a 'point' in the 'space of its associated time-system.' This space of a time-system is called 'time-less' because its points have no special relation to any one moment of its associated time-system.
Each event-particle is contained in one and only one point of each time-system, and will be said to 'occupy' such a point. Two points of the same time-system never intersect; two point-tracks which are respectively points in the spaces of different time-systems either do not intersect or intersect in one event-particle only.
Since each point-track intersects any moment in one and only one event-particle, two co-momental event-particles cannot lie on the same point-track. A pair of sequent event-particles lie in one and only one point-track, apart from exceptional cases when they lie in 'null-tracks.' Null-tracks are introduced later in [article 45].
42.4 In the four-dimensional geometry of event-particles it has already been pointed out that rects have the character of straight lines, but that since sequent event-particles do not lie on the same rect there is a missing set of straight lines required to complete the geometry. Point-tracks [together with the exceptional set of loci termed 'null-tracks'] form this missing set of straight lines for this geometry of event-particles.