Note Note 15 — § 4 THE DIFFICULTIES IN THE PRINCIPLES OF CLASSICAL MECHANICS
Henry L. (Henry Leopold) Brose translation
(p, 38). The term "inertial system" was originally not associated with the system, which Neumann attached to the hypothetical body . Nowadays it is generally understood to signify a rectilinear system of co-ordinates, relatively to which a point-mass, which is only subject to its own inertia, moves uniformly in a straight line. Whereas C. Neumann only invented the body , as an absolutely hypothetical configuration, in order to be able to formulate the law of inertia, later researches, especially those of Lange, tended to show that, on the basis of rigorous kinematical considerations, a co-ordinate system could be derived, which would possess the properties of such an inertial system. However, as C. Neumann and J. Petzoldt have demonstrated, these developments contain faulty assumptions, and give the law of inertia no firmer basis than the body introduced by Neumann.
