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On the Electrodynamics of Moving Systems II.

By Prof. Emil Cohn

in Straßburg i. E.

Submitted by Mr. Warburg.

Some years ago, I gave an extension of Maxwell's equation for moving bodies, which was in agreement with all then known facts.^[1] This approach was found in an inductive way, and has proven itself with respect to subsequent experiences. The decisive test concerns the case of uniform translational velocity; the special case of the equations which corresponds to this case, seems unquestionable to me. Up to now, the general equations were not subject to an equally strict experimental test. In the course of their development, I was led by the principle of "scientific economy";^[2] nevertheless, it may be that there can be found a simpler way, which is in agreement with facts as well. Meanwhile, it may be allowed for me, to develop here the characteristic features of that kind of electrodynamics, which follow from my equations. The resulting theorems are in full factual agreement with the content of my older treatise, as far as the properties of the electromagnetic field are concerned; with respect to mechanical forces, they partly deviate from them. That the determination of these forces was arbitrary to some extent, was particularly emphasized by me at that time.

§ 1. The fundamental equations.

They read:

$-\int \limits _{\circ }{\mathsf {E}}_{s}ds={\frac {d}{dt}}\int {\mathfrak {M}}_{N}dS$

I

1. Göttinger Nachrichten 1901, Heft 1; Ann. der Physik 7, 8.29, 1902.
2. See Sitzungsber. 1904, 46, S. 1300 f.