146 PHYSICS OF THE ELECTRON 



by J. J. Thomson and Lenard of the negative charges emitted by 

 a negatively charged metallic surface under the action of light and of 

 those spontaneously emitted by incandescent bodies also show an 

 identity with the cathode rays. Wehnelt has recently shown that the 

 oxides of the alkaline earths possess in an extraordinary degree this 

 property of spontaneously emitting cathode rays at high tempera- 

 tures, and furnishes a means of performing, on this particular kind 

 of rays, simple and exact measurements. 



Finally, we know that the magnitude of the Zeeman effect, in the 

 lease where the spectrum lines considered present the appearance of 

 a normal triplet, leads to the conclusion that the light corresponding 

 to these lines is emitted by negatively electrified centres, present in 

 matter and having the same ratio ^ as the cathode rays. 



Moreover, the magnitude of this ratio, one thousand to two thou- 

 sand times greater than for the hydrogen atom in electrolysis, leads 

 us, as a consequence of the identity of charges established by Town- 

 send, to consider the mass of the cathode corpuscle as one thousand 

 times smaller at least than an atom of hydrogen ; a result in perfect 

 agreement with the conception which makes material atoms an agglom- 

 eration of electrons of two kinds. On the hypothesis that the mass 

 is entirely of electromagnetic origin, the knowledge of the ratio e m 

 gives for the electron a sufficiently small radius (10~ 13 centimeters 

 about) in order to be, conformably to our conception also, negligible 

 in comparison with atomic dimensions. 



(35) Flames. The small mass of the cathode corpuscle, and the 

 possibility of separating from matter electrified centres a thousand 

 times smaller than the smallest atom, is confirmed by the mobility 

 of the negative ions in flames. We obtain enormous mobility com- 

 pared to that observed in gases at ordinary temperatures, and the 

 methods of the kinetic theory of gases permits us to calculate, by 

 means of this experimental mobility, that the movable negative 

 centres in flames have a mass about a thousand times smaller than 

 the hydrogen atom, and should consequently be identical with the 

 cathode corpuscles. At ordinary temperatures the negative ions are 

 less mobile because the cathode corpuscles surround themselves with 

 neutral molecules by simple electrostatic attraction, and form an 

 agglomeration which the feeble agitation allows to remain stable. 



VII. Positive Electrons --a Rays 



(36) Goldstein Rays, a Rays. Our knowledge of the structure of 

 positive charges is much less advanced than for the negative. Two 

 important cases show us the existence of positively charged particles, 

 besides the positive ions in conducting gases, which at ordinary tem- 

 peratures consist of an agglomeration of neutral molecules around 



