of Gases exposed to Rontgen Rays. 



243 



the inductor is opposite in sign to the charged wire, the effect 

 can in no way be due to conduction through the Rontgenized 

 air from the charged electrode to the inductor, since the 

 inductor would then be charged to the same sign as the 

 electrode. 



A small plug of glass wool placed in the metal tube between 

 the generator and the inductor completely stopped all electri- 

 fication, and the inductor received no charge, however rapid 

 a blast of air was sent through the apparatus. 



On account of the large quantity of air blown through the 

 inductor in order to obtain a convenient deflexion on the 

 electrometer (an amount sufficient to fill the inductor many 

 times over), only a small proportion of the charge could be 

 blown out. If, however, a gentle current of electrified air 

 was blown into the inductor for two or three seconds, and the 

 rays then stopped, it was found possible to blow out most of 

 the charge again, after a short interval, provided there was a 

 fairly wide opening in the inductor. If the opening was 

 stopped with a plug of glass wool, it was found impossible to 

 blow out the slightest amount, since the electrified particles 

 gave up their charge freely to the glass wool. 



Since the glass wool has the power of completely dis- 

 charging the electrification both positive and negative, a 

 short wide metal cylinder lightly packed with glass wool was 

 used instead of the inductor for testing the amount of the 

 electrification in most of the experiments that follow. 



The amount of electrification obtained varied with the 

 potential of the charged wire and the velocity of the current 

 of air. The relation between the amount of electrification 

 and the E.M.F. of the charged wire is shown in the Table 

 below : — 



E.M.F. in volts. 



Amount of Electrification 

 in scale-divisions. 



17 



35 



70 



200 



60 

 100 

 130 



82 



The amount of electrification increases up to a certain 

 point and then diminishes. The maximum amount of elec- 

 trification is closely connected with the value of the E.M.F. 

 which is just sufficient to give the saturation-value of the 



U2 



