226 Conductivity produced in Gases hy Negatively charged Ions. 



The ionization produced by the rays in the space between 

 the electrodes is practically uniform. Jn order that new ions 

 should be produced by collisions, it is necessary that negative 

 ions should pass through the gas near the inner electrode 

 where the force is large. When the inner electrode is 

 positive, all the negative ions pass through this region and a 

 large conductivity is obtained. When the inner electrode is 

 negative, only a few of the negative ions pass through the 

 space where the force is large, and consequently the con- 

 ductivity is not much increased. It can be easily seen that 

 by varying the shapes of the electrodes, the conductivity 

 may undergo various changes; and by having the inner 

 electrode very small, a phenomenon resembling unipolar con- 

 ductivity can be obtained. 



These results show that the increase in conductivity must 

 be attributed to the negative ions, and that the positive ions 

 do not generate new ions in the cases which we have been 

 considering. We have thus obtained experimental evidence 

 to show that positive and negative ions have very different 

 physical properties. 



14. The conclusions which have been arrived at in this paper 

 help to explain some other phenomena connected with the 

 passage of electricity through gases. The cases I have dealt 

 with are probably the simplest ; the experiments can be 

 easily arranged so as to test the theory, and furnish data from 

 which we can arrive at definite conclusions. 



Professor Thomson * and Dr. H. A. Wilson | have given 

 explanations of some of the phenomena connected with dis- 

 charge-tubes based upon the supposition that ionization is 

 produced by moving ions. In these cases, the phenomena 

 are very complicated, and it is by no means evident that the 

 ionization is principally due to this effect when the electric 

 intensity is small. 



Thus in the positive column where the force is of the order 

 of oO volts per centimetre, the ionization produced by moving 

 ions must be very small as can be seen from the curve tig. 7, 

 which gives the values of a for small forces. Moreover, 

 there is evidence of other effects which produce ionization. 

 It has been found by E Wiedemann J that rays are produced 

 in a discharge-tube which are analogous to Rontgen rays, 

 and produce ionization, so that their effect cannot be neglected 

 in the investigation. 



]f we consider the results of experiments on the potential 



* J. J. Thomson, Phil. Mag. September 1900. 



t H. A. Wilson, Phil. Mag-. June 1900. 



% E. Wiedemann, Zeitschrift filr Electrochemie. 



