An analysis of composite inertial motion (relativistic sum) within the framework of special relativity leads to the conclusion that every translational motion must be the symmetrically composite relativistic sum of a finite number of quanta of velocity. It is shown that the resulting space-time geometry is Gaussian and the four-vector calculus has its roots in the complex-number algebra, furthermore, that Einstein's "relativity of simultaneity" is based on a misinterpretation of the principle of relativity. Among others predictions of the experimentally verified rise of the interaction-radii of hadrons in high energetic collisions are derived. From the theory also follows the equivalence of relativistically dilated time and relativistic mass as well as the existence of a quantum of time (fundamental length) and its quantitative value, to be found in good accord with experiment Key Words: Special Relativity -quantization of velocity, length and time -rise of cross-sections and interaction-radii Inserting the respective result of (31) into (6a) yields N -N . If E* is given in GeV, for