-dimension, is suppressed, so that these moments are diagrammatically represented as two-dimensional. Point-tracks (in this case

-points) are represented by dotted lines. The diagram has the defect of representing matrices, such as

, by levels, and is thus liable to lead to unfounded assumptions.

49.3 Lengths on all rects, whether or no they be

-rects, are measurable in terms of one unit length. But time-lapses between

-moments—or, what is the same thing, time-lapses along