Wheelock — Nature of Ionization Produced hy a Rays. 241 



Again the ratio of deflections is approximately constant.* 

 This" could not be so if volume ionization existed, since the 

 density of ionization in the one case would be twenty-nine 

 times the density in the other, and general recombination would 

 have a very different effect in the two cases. 



(c) Experiments were then made with the held at right 

 angles to the path of the a particle, in which fan-shaped beams 

 of different sizes and sliapes were used. These were obtained 

 by placing slits of different dimensions over the source. 



The different beams used were as shown in fig. 4, 



Fig. 4. 



r 



- - -. - ^ 



'' A-''' 



■" ^>' 1 



\\ts\ ■■ .^11 1 



1. 'A _ _ 

 >> 



— i!-\ 



A 



B 



c 



Slit 



Slit 



Slit 



5 X 0-5°'"' 



5x0-2'»°> 



0-5xl-5"''° 



Perpendicular Field. 



Source 2*6 cm. from the middle of the chamber. 

 Current 





, 



A 





Ratio of Currents 



)lts / cm. 



A 



Slit 

 5x0-5™°' 



B 



Slit 

 5 X O-S"" 



C 



Slit 



0-5 X ] -5™" 



A/B 



A/C 



C/B 



2-1 



9-88 



2-57 



3-7 



3-84 



2-67 



1-44 



10-6 



17-33 



3-35 



5-36 



5-17 



3-23 



1-6 



21-0 



20-0 



3-65 



5-77 



5-48 



3-47 



1-58 



43-0 



22-2 



3-9 



6-29 



5-7 



3-53 



1-61 



85-5 



23-6 



4-07 



6-56 



5-8 



3-58 



1-61 



211-5 



24-1 



4-15 



6-68 



5-8 



3-6 



1-61 



From the above data it will be seen that the ratio of the 

 currents C/B is practically constant. The ionization in both 

 of these cases is small and the result appears to indicate that 

 there are not enough columns in the chamber at any time to 

 get interference of the ions of one column with those of 

 another. 



* It is interesting to observe, that to compare the ionization produced by 

 a rays from different sources, it is not necessary to obtain the saturation 

 value of the current. This is very convenient, since for ionization by a rays 

 saturation is obtained only when the potential difference between the plates 

 is very large, when the field is applied parallel to the path of the a particle. 



