equations of motion of the electron could be reduced to those of general mechanics.
Bucherer: I suspect that Maxwell's equations can be reduced to the Lagrangian form. I have not yet investigated this particular question, but I suppose it is possible, because I use Maxwell's equations without modification for the quasi-stationary motion, but I don't like to say anything definitive.
Abraham: If you look at the numbers, it is clear from them that the deviations of Lorentz's theory are at least twice as large as those of my own, so it may be said that the sphere theory represents the deflectability of the β-rays twice as good as the relative theory. (Great laughter.) When I consider what was the state of the question 5 years ago when I began my involvement with it, so I must be satisfied with the results; for I did not believe at first that the formula agrees with the experiments, and I was very surprised when Kaufmann told me one day that the formula agreed well with the more refined measurements. However, I see the advantage of the sphere over the relative theory not only in better agreement with the measurements, but also in the fact that it is a purely electromagnetic theory. We started from the question of whether the mass of the electron is a purely electromagnetic quantity. The sphere theory answers this question; it considers the energy of cathode rays as purely electromagnetic. The approaches to the electromagnetic energy density was also taken as a basis by Lorentz. However, the Lorentz electron has a kind of internal potential energy in addition to the electromagnetic energy, as I have shown and what is still not refuted. In the relative theory one would therefore not consider the cathode rays as purely electromagnetic processes, but as processes which cannot be explained by electrodynamics.
Gans: I would like to point out that any assumption about form-changes of the electron in motion brings, of course, more parameters into the theory, so that one can better adjust himself to the phenomena.
The Michelson-Morley and the Trouton-Noble experiment require a certain difference of the longitudinal and transverse dilatations, yet the ratio remains undetermined.
Yet, one could create more theories for which this ratio of the longitudinal to transverse dilatation always has different values; one would explain the phenomena of Becquerel best, but you could not say it is the best; it would only be a retroactive adjustment to the phenomena.
Planck: Abraham is right when he says the main advantage of the sphere theory would be that it would be a purely electrical theory. If this were feasible that would be very nice, for now it is only a postulate. The Lorentz-Einstein theory is based on a postulate, namely that no absolute translation can be demonstrated. It seems that the two postulates can not be united, and now it depends on which postulate is to be preferred. That of Lorentz is more sympathetic to me. It's probably the best thing when work continues in both areas and the experiments eventually give the decision.
Sommerfeld (Munich): The pessimistic view of Planck I wouldn't like to join for the time being. Because of the extraordinary difficulty of measuring, perhaps the deviations could have their reason in unknown sources of error. As to the question of principle formulated by Planck, I would suspect that the gentlemen under 40 years prefer the electrodynamic postulate, that those over 40 years prefer the mechanical-relativistic postulate. I prefer the electrodynamic. (Laughter.)
Kaufmann: To the postulate-question I would like to say that the epistemological value of the postulate of relative motion is, however, not very large, as it is only useful for uniform translation. As soon as we take into account rotation and irregular motions, we don't get along with it. Maybe one is trying to banish the aether (which is often perceived as uncomfortable) out of the world, but one has to introduce it in the case of rotational motions, such as in the case of the flattening of celestial bodies.
Planck: Of course, this is only about uniform translation. Irregular motion can already be demonstrated by mechanics, but uniform motion cannot. The requirement is, what cannot be verified in mechanics, cannot be verified in electrodynamics.
