The direction of {rho} in the instantaneous space of the moment M is the direction of {beta} in M, where M is a moment of time-system {alpha}.

Again the matrix of the line r of space {alpha} will also be the matrix of some line s of space {beta} which will be in the direction of {alpha} in space {beta}.

Thus if the lorry halts at some point P of space {alpha} which lies on the line r, it is now moving along the line s of space {beta}.

This is the theory of relative motion; the common matrix is the bond which connects the motion of {beta} in space {alpha} with the motions of {alpha} in space {beta}.
Motion is essentially a relation between some object of nature and the one timeless space of a time-system.

An instantaneous space is static, being related to the static nature at an instant.