Two Ions produced in Gases by Rontgen Radiation. 151 



the fall of potential near the plates is very large, and the 

 charges extend all through the space between them. 



In the ease above (tig. L3) the fall of potential at the 

 cathode was j of a volt, being more than one third of the 

 total potential of the plate. This fall was due to the presence 

 of electrification of an average density less than 2 X 10 -4 

 (fig. II). If we take the charge on each carrier to he the 



Fig. 14 







Units 





ixlO 4 





Positive 







P/ate 



I , 



2 



3 





CM 



} 



Negative 



Plate 





J 















atomic charge, or about 10~ 10 absolute units, it would require 

 about 10 6 carriers per c.c. to produce the density observed. 

 Taking the number of molecules in 1 c. c. as 10 20 , the ratio 

 of the excess carriers to the total number of molecules is 



given by -— q. From calculations based on the current passing- 

 through a gas during conduction under Rontgen radiation, it 

 is known that we are able to obtain an ionization that is 

 between 100 and 1000 times as large as this ratio: so that, 

 by a sufficient separation of the two kinds of ions, it is possible 

 to have a fall of potential amounting to more than 100 volts, 

 a value comparable to that due possibly to the same cause, at 

 the electrodes in discbarge-tubes. 



In determining the ratio of the velocities of the two ions 

 by the method described in §1, it is now evident that it was 

 important to know the potential gradient in the apparatus used 

 (§2) for the conditions under which the readings were taken. 



