CONSTITUTION OF MATTER RUTHERFORD. 175 



through a vacuum tube at very low pressures a peculiar type of ra- 

 diation appeared, laiown as the cathode rays. This radiation ap- 

 peared to be projected from the cathode in straight lines and, unlike 

 light, was deflected by a magnet. These rays excited strong phos- 

 phorescence in many substances in wdiich they fell and also produced 

 marked heating effects. Crookes concluded that the cathode rays 

 consisted of a stream of negatively charged particles moving at high 

 speed. The general properties of this radiation appeared so re- 

 markable that Crookes concluded that the material constituting the 

 cathode stream corresponded to a " new or fourth state of matter." 

 After a controversy extending over 20 years the true nature of these 

 rays was finally independently shown in 1897 by the experiments of 

 Weichert and Sir J. J. Thomson. They proved, as Crookes had sur- 

 mised, that the rays consisted of a stream of negatively charged 

 particles traveling with enormous velocities from 10,000 to 100,000 

 miles a second, depending on the potential applied to the vacuum 

 tube. In addition, it was found that the mass of the particle was ex- 

 ceedingly small, about one eighteen-hundredth of the mass of the 

 hydrogen atom, the lightest atom known to science. These results 

 were soon confirmed and widely extended. These corpuscles, or elec- 

 trons, as they are now termed, were found to be liberated from mat- 

 ter not only in an electric discharge but by a variety of other agencies : 

 For example, from a metal on which ultra-violet light falls and also 

 in enormous numbers from an incandescent body. Radium and other 

 radioactive substances were found to emit them spontaneously at 

 much greater speeds than those observed in a vacuum tube. It thus 

 appeared that the electrons must be a constituent of the atoms of mat- 

 ter and could be released from the atom by a variety of agencies. 

 This idea was much widened and strengthened by the investigations 

 of Zeeman and Lorentz, who showed that the radiation of light must 

 be mainly ascribed to the movements of electrons of the same small 

 mass within the atom. 



It does not fall wdthin the scope of my address to outline the 

 very important consequences that followed in many directions from 

 this fundamental discovery of the independent existence of the 

 electron and its connection with matter. It Avas found by Kauf- 

 mann that the mass of the electron was not a constant, but in- 

 creased with its speed, and from this result it was deduced that 

 the electron was an atom of disembodied or condensed electricity 

 occupying an exceedingly small volume whose mass was entirely 

 electrical in origin. 



UNIT OF ELECTRICITY. 



I should mention here one important consequence that has fol- 

 lowed from these discoveries. From the laws Avhich control the 

 passage of electricity in conducting solutions, Faraday recognized 



