DEMONSTRATION OF ELECTRON WAVES 547 



unbalanced in one direction or the other by one or more electronic 

 units. Yet this remained largely a speculation until the study of the 

 conductivity imparted to gases by X-rays made all other views unten- 

 able. Ions of both signs are formed at a uniform rate within the body 

 of a gas subjected to this then newly discovered radiation ; their charges 

 are ionic; they move through the gas by diffusion and under the in- 

 fluence of an impressed electric field; they disappear through recom- 

 bination. 



Other ideas now familiar were not entirely novel even in 1890; for 

 instance, the idea that positive and negative electrons possess mass as 

 well as charge — that those of one sign are more massive than the 

 other — that within the atom the lighter revolve about the heavier 

 ones. Weber, following on Ampere, had pictured a mechanism of this 

 kind to explain the magnetic properties of materials. All these notions 

 became much more plausible, however, when Lorentz showed (as he 

 did in 1897) that the splitting and polarization of spectral lines by a 

 magnetic field might be explained as the effect of the field upon the 

 period of revolving particles such as Weber had assumed, and that 

 from the magnitude of this so-called "Zeeman effect" one might ac- 

 tually calculate the ratio of the charge of the particle to its mass. The 

 •value so found was greater by a factor 2000, or thereabouts, than the 

 similar ratio for hydrogen ions in electrolysis. If the charge of the 

 particle were indeed the electronic charge, then the mass of the particle 

 was about 1/2000 only of the mass of the hydrogen atom — a highly 

 acceptable conclusion. The concept of the electron had gained much 

 in definiteness, and so also had that of the atom. 



But more illuminating still was the discovery made in the same year 

 that the trajectories followed by cathode rays in traversing electric 

 and magnetic fields are exactly those to be expected if these rays are 

 streams of swiftly moving negatively charged particles with a charge to 

 mass ratio amounting again, as in the foregoing instance, to about 

 1/2000 that of the hydrogen ion. There could be little doubt that this 

 was the very particle inferred by Lorentz from the "Zeeman effect." 

 Cathode rays were certainly streams of free negative electrons — un- 

 attached to atoms. This supremely important discovery was made 

 by J. J- Thomson in England and by Wiechert in Germany. 



The conception of the negative electron as a subatomic particle 

 possessing mass as well as charge, capable of independent existence, 

 and subject to the laws of classical electrodynamics now seemed clearly 

 established. If various of the simple relationships were at this time 

 sensed rather than demonstrated — such, for example, as the exact iden- 

 tity of the charge to mass ratios of the Zeeman effect particle and the 



