Such moments will be said to lie 'outside' the given duration.
Again other moments of the family are such that the shorter durations in their composition are parts of the given duration.

Such moments are said to lie 'within' the given duration or to 'inhere' in it.

The whole family of parallel moments is accounted for in this way by reference to any given duration of the associated family of durations.

Namely, there are moments of the family which lie without the given duration, there are the two moments which are the boundary moments of the given duration, and the moments which lie within the given duration.
Furthermore any two moments of the same family are the boundary moments of some one duration of the associated family of durations.
It is now possible to define the serial relation of temporal order among the moments of a family.

For let A and C be any two moments of the family, these moments are the boundary moments of one duration d of the associated family, and any moment B which lies within the duration d will be said to lie between the moments A and C.Thus the three-termed relation of 'lying-between' as relating three moments A, B, and C is completely defined.