282 Genesis of Ions in Discharge of Electricity through Gases. 



conclusion that there is one centre of ionization close to the 

 cathode, and another in the negative glow. 



According to the view taken in this paper, these centres 

 form mutually dependent and, as it were, regenerative sys- 

 tems, — the ionization in the negative glow being due to the 

 corpuscles coming from the centre close to the cathode, 

 while the ionization close to the cathode is due to the positive 

 ions which come from the centre in the negative glow. This 

 view seems in accordance with the experiments of Villard *, 

 in which a screen placed between the negative glow and the 

 cathode stopped the emission of cathode-rays from the portion 

 of the cathode shielded by the screen. 



The negative corpuscles starting from the cathode ionize 

 the gas in the neighbourhood of the magnetic glow, producing 

 in this region a large number of ions ; this makes the region 

 one of great electrical conductivity, and the electric force 

 consequently falls to a very small value. Let us now trace 

 what would happen if there were no centre of ionization 

 between the negative glow and the anode : the current in this 

 part of the tube would be carried by the negative ions pro- 

 duced in the negative glow, such a distribution of ions in the 

 tube would cause the electric force to increase as we approach 

 the anode, and, if this increase did not cause the kinetic 

 •">ergy of the ions to exceed the value at which they begin to 

 °e other ions, the electric force would increase uninter- 

 up to the anode. If, however, the electric force 

 co such an extent that the energy the field commu- 

 .rfcsn'es to the ions is greater than that required for the disso- 

 ciation of the surrounding molecules into other ions, then in 

 the region where the electric force reaches this value fresh 

 ions will be produced. This will increase the conductivity of 

 the gas, and therefore cause the electric force to diminish : 

 thus, after reaching a certain value, the electric force will fall 

 off, and then begin to increase again after it has sunk below 

 the value at which ionization takes place. If this were repeated 

 several times before the anode was reached, we should get the 

 electric force waxing and waning, as it does in the striated 

 discharge. The view that the striations consist of alternations 

 of layers of high conductivity due to the ionization of the gas 

 by an electric force exceeding a certain critical value, with 

 layers of gas through which the electric force is too low to 

 produce ionization, accounts for the distance between the 

 striations diminishing as the density of the gas increases, and 

 also for the distance between the striations in a tube of 

 unequal bore being less in the narrow than in the broad parts 

 * Yillavd, Journal de Physique, Jan. 1900. 



