Produced by Rontgen Rays. 



47 



positions relative to S, it was found that the discharge in the 

 X-ray tube began practically simultaneously with the opening 

 of the key S, increased to a maximum and then fell to zero, 

 the total duration of the flash being 0*0035 seconds. The limit- 

 ing position of the key F at which the discharge ceased could be 

 determined within a distance corresponding to 0*0001 seconds. 

 The calibration of the pendulum, as determined by the con- 

 denser method described above, was corrected for the time 



Fig. 4. 



2O0 



DCFtrci 



10M5 

















/ 



y 



B 





160 























y 



s 















/ 







y 



,'x. 























y 























' 



/ 











8n 













y 



'' 

















S 



/ 





y 



















Ps f 



C 





yf* 







F 









*- 



& 



4U 



1/* 





> 



r^^ 



^— 



-— — H 













-fi 



























-J 



PRESSURE 



occupied by the flash by subtracting 0*0015 seconds from each 

 value. It was necessary to know the total duration of the flash 

 accurately also for a special experiment to be described. 



Preliminary Experiment. 



In order to ascertain the effect of secondary and corpuscular 

 radiation from the electrodes A and B of fig. 1, the lead screens 

 M M 7 and N W were removed, allowing the Bontgen rays to 

 fall on A and B as well as in the space between them. The 

 plate A was charged continuously to 160 volts. Air was intro- 

 duced into the chamber K and a series of deflections noted for 

 different pressures, using single flashes of X-rays of constant 

 intensity. The air was then pumped out and similar readings 

 taken for hydrogen. The results are plotted in fig. 4, where 

 the abscissae represent pressure in millimeters of mercury, and 



