Homogeneous Corpuscular Radiation. 



353 



air, would be unaltered fey the change in sign of the potential 

 of the ionization-chamber. The negative ions produced by 

 these two sources of radiation will thus communicate a 

 negative charge to the plate R 2 equal to the positive charge 

 imparted in the former case. But the negative corpuscles 

 emitted by the plate R 2 carry away a negative charge, and 

 this is equivalent to giving an equal positive charge to it. 

 Thus the total loss of charge by the plate will be less in this 

 case than in the former. 



Let q 1 be the charge carried to the plate by the ions pro- 

 duced by the secondary exciting beam in 1 cm. of air. Let 

 q 2 be the charge carried to the plate by the ions produced by 

 the corpuscular radiation. 



Let q z be the charge carried away from the plate by the 

 corpuscles themselves. 



Then the true measure of the ratio which we have called 

 R is q 2 /q^ 



The ratio experimentally determined from the readings of 

 the electroscopes E 2 and E 3 , as previously described, is really 



92 + q* 



qi+q* 



when the ionization-chamber is charged to +240 volts, and 



qi-Qz 



when the chamber is charged to — 240 volts. 



Below are given the values of these ratios when copper is 

 used as the tertiary radiator and silver as a source of the 

 secondary homogeneous Rontgen beam. 



Table VI. 



Voltage on Ionization-Chamber. 



Value of Katio. 



+240 

 -240 

 +240 



•547 

 •545 

 •540 



It will be seen that within the limits of experimental error 

 the ratios are identical in value, and cannot appreciably differ 

 from the theoretical ratio R. 



It appears from this result that q 3 must be small compared 

 Phil. Mag. S. 6. Vol. 19. No. 111. Marsh 1910. 2 A 



