Such abstractive elements are rectilinear routes.
They are the segments of instantaneous straight lines which are the ideals of exact perception.

Our actual perception, however exact, will be the perception of a small event sufficiently far down one of the abstractive sets of the abstractive element.
A station is a vagrant route and no moment can intersect any station in more than one event-particle.

Thus a station carries with it a comparison of the positions in their respective moments of the event-particles covered by it.

Rects arise from the intersection of moments.

But as yet no properties of events have been mentioned by which any analogous vagrant loci can be found out.
The general problem for our investigation is to determine a method of comparison of position in one instantaneous space with positions in other instantaneous spaces.