Metals under the Influence of Alpha Rays. 



325 



The values of s given in the second column of Tahle IV are 

 means of the two values thus obtained. 



Table IV. 

 a=l-24 6=0-20 m=0-65 w=0'10. 



Volts 



s 



y 



obs. 



3 



calc. 



V 

 obs. 



calc. 



Vi 

 obs. 



calc. 



40 



1-39 



2-82 



2-83 



2-15 



2-14 



1-36 



1-38 



100 



1-20 



2-63 



2-64 



2-00 



2-02 



1-35 



1-36 



200 



0-90 



2-35 



2-34 



1-85 



1-82 



1-33 



1-33 



300 



0-71 



2-16 



2-15 



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*2!* 



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 



0-25 



1-68 



1-69 



1-41 



1-40 



1-26 



1-26 



In this table the columns under " observed " are taken from 

 the experimental curves ; the columns under "calculated" 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 corre- 

 sponds 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 Ra C, when the distance between the 

 source and the ionization chamber was varied. He attributes 

 the soft primary radiation to the recoil atoms of Ra D, and it 

 seems very probable that this view is correct. His results 

 differ from ours, however, in the relative magnitudes of the 

 effects of the different types of rays. Thus he states (1. c, 

 page 19) that, in a narrow ionization chamber and with a clean 

 active surface, the soft primary rays (recoil atoms) may make 

 five times as many ions as the a-rays. In our experiments the 

 current of S-electrons produced by the soft primary radiation 

 is only 1/6 of that produced by the a-rays. This discrepancy 

 is due, at least in part, to the fact that the deposit of polonium 

 which we used could not be regarded as " thin " in regard to 



Am. Jour. Sci.— Fourth Series, Vol. XXXIV, No. 202.— October, 1912. 



22 



