148 PHYSICS OF THE ELECTRON 



acquire if it emits only a rays. However high may be the vacuum 

 around a piece of radioactive bismuth, or polonium, it does not 

 acquire any charge, and loses rapidly, on the contrary, its positive or 

 negative charge. Possibly one might explain this discharge by the 

 ionizing action of the a rays on the gas, however rare. The passage 

 of a particles, projectiles of large dimensions, through the surface of 

 radioactive bodies from which they come, can play the same part 

 as the impact of Kanalstrahlen on the surface of the cathode, and 

 cause the emission of cathode rays of very little penetrating power, 

 whose presence would suffice, added to that of the a rays, to prevent 

 any permanent charge of the radioactive body, whatever may be its 

 sign. 



(39) The Positive Electrons. If the positive centres, as we know, 

 ought not to be represented as free electrons, it seems, however, 

 necessary to admit the presence of probable electrons which cause the 

 neutralization of the negative charges in the atomic structure, but 

 which for some reason come out of this structure with extreme diffi- 

 culty, contrary to what is the case for the negative centres. More- 

 over, it would appear necessary in order that the theory of metals, 

 which ascribes their conductivity to the presence of free electrified 

 centres moving under the action of a field can take account of all the 

 facts, the Hall effect in particular, of variable sign in different metals, 

 that the centres of two kinds coexist in the metal, free to move about 

 in all directions. These positive centres do not appear to be the 

 metallic atoms themselves, necessarily immovable in order to main- 

 tain the solid framework of the metal. It is possible that the positive 

 electron, which no known action in a gas can maintain separate 

 from the atomic material, may be free in large numbers in the en- 

 tirely different medium which constitutes the metal. Many problems 

 present themselves here on the subject of the nature of the positive 

 charges. 



VIII. Theory of Matter. Radioactivity 



(40) Atomic Instability. Let us examine now a little more closely 

 the consequences to which we are led by the conception of matter 

 as made up of electrons of two signs, of atoms formed of electrified 

 bodies in motion under their mutual actions. From the first, outside 

 of gravitation, whose intensity is infinitely small compared to the 

 electromagnetic forces in the interior of atoms which determine all 

 the physical and chemical changes of state, the elementary laws of 

 action reduce to the forces of Lorentz, which allow us, as we have seen, 

 to calculate the acceleration to which an electron is subjected as 

 function of the electric and magnetic fields produced by the other 

 electrons at the point where the first electron is situated. In the case 



