It follows from this axiom that two objects at rest in any two points of a time-system {beta} are moving with equal velocities in any other time-system {alpha} along parallel lines.

Thus we can speak of the velocity in {alpha} due to the time-system {beta} without specifying any particular point in {beta}.

The axiom also enables us to measure time in any time-system; but does not enable us to compare times in different time-systems.
The second axiom of congruence concerns parallelograms on congruent bases and between the same parallels, which have also their other pairs of sides parallel.

The axiom asserts that the rect joining the two event-particles of intersection of the diagonals is parallel to the rect on which the bases lie.

By the aid of this axiom it easily follows that the diagonals of a parallelogram bisect each other.
Congruence is extended in any space beyond parallel rects to all rects by two axioms depending on perpendicularity.