The details of the effects, which result from the relativity of space-time measurements, have so frequently been discussed in recent years that it is only possible to repeat what has already often been said. The essential point in the discussion of [this section] is the recognition of the fact that space and time represent a homogeneous manifold of "four" dimensions, with homogeneous measure-relations (vide [Note 14]). Consequently, to be consistent, we must apply .the arguments of the preceding [§ 3(a)] about the measure-relations to the four-dimensional space-time-manifold; and, in view of the two fundamental postulates (1) of continuity and (2) of relativity, and including the time-measurement as the fourth dimension, we must select for our line-element the expression:
in which the
(
) are functions of the variables
,
