Toward the end of the nineteenth century Lorentz modeled the electron (“vibrating charged particle,” as he called it) by a spherical shell of uniform surface charge density and set about the difficult task of deriving the equation of motion of this electron model by determining, from Maxwell's equations and the Lorentz force law, the retarded self electromagnetic force that the fields of the accelerating charge distribution exert upon the charge itself [1]. (This initial work of Lorentz in 1892 on a moving charged sphere appeared five years before J.J. Thomson's “discovery” of the electron. It is summarized in English by J.Z. Buchwald [2, app. 7].) With the help of Abraham,¹ a highly successful theory of the moving electron model was completed by the early 1900's [3, 4]. Before Einstein's papers [5, 6] on special relativity appeared in 1905, they had derived the following force equation of motion