It was assumed that the magnitude of their negative electric charge was equal to that of the electron, and so to account for the difference in curvature, it was supposed that their mass was greater than an electron but smaller than a proton.
Asúmese que a magnitude da súa carga eléctrica negativa é igual á do electrón e, daquela, para ter en conta a diferenza de curvatura, supúxose que a súa masa era maior cá do electrón, aínda que menor da dun protón.