41.3 Each event-particle in a duration is covered by one and only one station in that duration; and any event-particle covered by a station can be taken as the 'assigned event-particle' of the formative condition, inherent in every event which is a member of the station. Every station is a route; and also every station in a duration intersects every moment of that duration [i.e. inherent in it] in one and only one event-particle, and intersects no other moments of that time-system. It will be noted that a station is associated with a definite time-system, namely the time-system corresponding to its duration. 41.4 A station of one time-system either does not intersect a station of another time-system or intersects it in one event-particle only. Thus stations belong to the type of routes which have been denominated 'kinematic routes.' Each station exhibits an unchanging meaning of 'here' throughout the duration in which it is a station; namely, every event-particle in a station is 'here' in the duration in the same sense of 'here' as for every other event-particle in that station. 42. Point-Tracks and Points. 42.1 Consider all the durations belonging to one time-system. Of these durations some intersect each other, and some are parts of others. Thus any event-particle is covered by many durations of this time-system, and lies in stations corresponding to these durations. We have now to consider the relations to each other of these various stations, each containing . The fundamental theorem is as follows: If and ′ be durations of the same time-system, and extends over ′, and if be an event-particle inhering in ′ and and ′ be the stations of in and ′ respectively, then covers ′. In other words used in less technical senses, If ′ be part of , then ′ is part of . 42.2 Any given station in a duration can thus be indefinitely prolonged throughout the time-system to which belongs. For let be any other duration of the same time-system which intersects in the duration ′ and also extends beyond . Then the part of which is included in ′, namely ′ (say), is a station in ′. Also there is one and only one station in , (say), which covers ′; and no other station in covers any event-particle of ′. 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.