Electrons by Metals under Influence of Alpha Rays. 179 



With these values we may calculate s for different values 

 of the potential on the case, from the curves, by the 

 equations 



_ vi—y \ . _ y* —y-2— n 



s — - , s — 



m — n 1 — m 



The values of s given in the second column of Table IV. 

 are means of the two values thus obtained. 



Table IV. 

 a = 1-24. b = 0-20. m = 0-65. n = 0*10. 



1 





V* 



y 





Vx 



Yolts. 



s. 



obs. 



calc. 



obs. 



calc. 



obs. 



calc. 



40 



1-39 



2-82 



2-83 



2-15 



2-14 



1-36 



138 



100 



1-20 



2-63 



2-64 



200 



2-02 



135 



1-36 



200 



0-90 



2-35 



234 



1-85 



T82 



1-33 



1-33 



300 



071 



2'16 



215 



1-74 



1-70 



1-31 



1-31 



400 



0-60 



2-05 



2-04 



1-65 



1-63 



1-30 



1-30 



500 



0-54 



1-98 



1-98 



1-59 



1-59 



1-29 



1-29 



600 



0-48 



1-91 



1-92 



1-54 



1-55 



1-28 



1-29 



700 



0-41 



1-85 



1-85 



1-50 



1-51 



1-28 



1-28 



800 



0-34 



1-78 



1-78 



1-46 



1-46 



1-27 



1-27 



900 



0-29 



1-73 



1-73 



1-43 



1-43 



1-27 



1-27 



1000 



025 



1-68 



1-69 



1-41 



1-40 



1-26 



1-26 



i 



In this table the columns under " observed " are taken 

 from the experimental curves ; the columns under " calcu- 

 lated w are obtained from equation (1) with values of the 

 constants given, and the values of s contained in the same 

 line of the table. It is obvious that the relation between the 

 three curves corresponds very closely to the hypothesis that, 

 in addition to a-rays, a radioactive body emits a very 

 absorbable primary radiation and that a secondary radiation 

 consisting of moderately swift electrons is emitted by the 

 source and also by any object which is struck by the 

 a-rays. 



This conclusion is in accord with the results of Werten- 

 stein, who measured the ionization produced in air at low 

 pressures by the radiations from RaC, when the distance 

 between the source and the ionization-chamber was varied. 

 He attributes the soft primary radiation to the recoil atoms 

 of RaD, and it seems very probable that this view is correct. 

 His results differ from ours, however/ in the relative magni- 

 tudes of the effects of the different types of rays. Thus he 

 states (/. c. page 19) that in a narrow ionization-chamber 

 and with a clean active surface, the soft primary rays (recoil 



