Walter Kaufmann, On the Constitution of the Electron
“ Abraham [19] alluded to the fact, that Lorentz's deformation of the electron requires the expenditure of work, so that one has to assume, to avoid a contradiction with the energy law, an "inner potential energy" of the electron; a pure electromagnetic foundation of the mechanics of the electron, and by that also of mechanics at all, would be proven to be impossible if new measurements should demonstrate the validity of Lorentz's theory. ”
Walter Kaufmann, On the Constitution of the Electron
“ The results accessible to observation are thus the same with respect to both authors; however, while Lorentz only shows that his hypotheses lead to the desired result without excluding that the same can also be achieved in another way, it is shown by Einstein, that when the desired result, namely the principle of relative motion, is placed at the top of the whole of physics, then the kinematics of the rigid body must necessarily be changed in the way stated, and that the equations of electrodynamics [18] must assume the form stated by Lorentz. ”
Walter Kaufmann, On the Constitution of the Electron
“ Since the same ratio of axis also applies to Lorentz's electron, one can derive the equations given by Bucherer for mass, energy, and momentum of the electron, without further ado from the ones of Lorentz, when one introduces, instead of the invariable transverse diameter of the electron that occurs as a parameter in the equations of Lorentz, a transverse diameter depending on the velocity, so to be measured that the volume of the ellipsoid is equal to the original sphere. ”
