of Electricity through Gases exposed to Rontgen Rays. 403 



at different points in the curve. When the intensity of these 

 rays is diminished } the saturation current is diminished in a 

 larger proportion than the current for small electromotive 

 forces. This is shown by the following diagram, which 

 represents the i and E curves through chlorine gas for dif- 

 ferent intensities of the Rontgen rays ; the weak radiation was 

 got by interposing a thick aluminium plate. In this diagram 



Fijr. 3. 



the ordinates for the weak radiation have been increased so 

 as to make the ordinate for the saturation current of the 

 weak radiation the same as that of the strong. When this is 

 done the rest of the "weak" curve is above the strong, 

 showing that the diminution in the radiation has affected the 

 saturation current to a greater extent than the weaker cur- 

 rents. The saturation current depends only on the number 

 of conducting particles produced by the rays ; for the smaller 

 currents the diminution in the number of molecules is to 

 some extent compensated for by the increase in the time 

 taken for these to recombine ; thus T is increased when the 

 intensity of the rays is diminished, so that, as we see from 

 equation (6), the proportion between a small current and the 

 saturation current is increased when the intensity of the rays 

 is diminished. 



Whatever is the magnitude of the electromotive force, a 

 diminution in the intensity of the rays is accompanied by a 

 diminution in the current, so that the 1 and E curves for two 

 intensities of radiation would not intersect if both were 

 drawn on the same scale. 



If, however, instead of keeping the gas the sunie and 

 altering the intensity of the radiation, we alter the gas and 



