of Recombination of the Ions of Gases. 427 



Immediately after the passage of the pendulum the lever 

 DF was replaced, thus reducing H to zero potential again. 

 In order to prevent a sudden deflexion of the electrometer 

 when the E.M.F. was applied to and removed from H, the 

 electrometer was not directly connected to L until the lever 

 had been replaced. The capacity M was introduced in order 

 to prevent the potential of the circuit LM rising to any con- 

 siderable extent when the E.M.F. was applied to H. 



It was found tbat applying and removing the E.M.F. alone 

 produced no effect on the electrometer ; but when the rays 

 had acted on the gas inside the vessel L, there was always a 

 deflexion in the electrometer, showing that the electrode L 

 had received a charge of the same sign as the pole of the 

 battery. 



Since the E.M.F. applied was usually over 200 volts, a 

 value sufficient to completely saturate the gas, the quantity 

 of electricity that passed through the gas was proportional to 

 n, the number of ions present in the gas at the instant the 

 E.M.F. was applied, while an immediate application of the 

 E.M.F. after the rays had ceased gave the total number N. 



The rate of recombination of the ions could thus be com- 

 pletely determined, as the times taken by the pendulum to 

 pass from one lever to the other could be very approximately 

 calculated. 



The following table shows the way in which the deflexion 

 of the electrometer varied with the time after the rays had 

 ceased, wdien the bell-jar was filled with dust-free air. 



Time in sec 



onds. 



Deflexion of electrometer, 



•004 





184 



•08 





183 



•45 





106 



2 





37 



4 





19 



The value of the deflexion is practically constant for nearly 

 j^q second after the rays have ceased. After an interval of 

 4 seconds the air still possesses appreciable conductivity. 



Since the gases have widely different conductivities under 

 the X rays, it is to be expected that the rate of recombination 

 is different for the various gases. 



The following table gives the times T for the number of 

 ions to fall to half their original number. The intensity of 

 the radiation was sensibly constant for all the gases. 



