Page:Zur Elektrodynamik bewegter Systeme I.djvu/8

 Conversely, as far as I can see, the form of equations (C) is specified by these two requirements. The vectors arising in them, can only be changed by additional vectors which contain derivatives of the velocities, i.e. in other words: any allowed generalization of (C'), which doesn't coincide with (C), should contain derivatives of second order when written in the form of differential equations. When one wants to avoid such complications, then any such theory – whatever its starting point may be – must lead to (C) in the general case, when it once formally led to (C') in the special case $$w=const.$$.

If these conclusions are justified, then everything that was said about the dual interpretation of special equations (C'), must transferred to the possible different interpretations of the general equations (C): then any conceptually expressible difference between them vanishes.

§ 6. The actual difference between the ian equation and the ones by me persists, as soon as one also considers the paramagnetic and diamagnetic bodies (what we have avoided here). My equations, as those of , are symmetric as regards the electric and magnetic magnitudes, while the ian ones are not. This appears as an essential feature of the theory of electrons: its starting equations already show it. Also with respect to this relation, an experimentum crucis seems to be excluded, although at this place (contrary to other differences) a deviation in expressions of first order exists. I intend to explain this more closely in the near future, and simultaneously to present the essential content of my mentioned treatise again, namely in a (as I think) more satisfactory form.

§ 7. Against the applicability of my equations – more precisely spoken of my interpretation of equations (C') – has raised an objection. According to these equations, as soon as $$x_{0}\dots t_{0}$$ are considered as true coordinates and times, the absolute (i.e. estimated with respect to a resting coordinate-system) speed of light $$V$$ in the direction $$\nu$$ is defined by $$\tfrac{1}{V-w_{\nu}}=\sqrt{\eta+1}+w_{v}$$ (l.c.,