110 , Mr. A. S. Eve on the Radioactive 



cessation of the charge, then C 2 V 2 is a l so a measure of the 

 emanation present in the tank. Therefore, whatever may be 

 the amount of emanation, whether naturally present or 

 artificially introduced, we should have, under all circumstances, 

 a constant value for the following percentage, namely, 



^ x 100 (1) 



The constancy of the quantity must, of course, depend 

 upon the current being fully saturated, and on the active 

 deposit being completely collected in every case. 



If a smaller vessel be now filled with the emanation of 

 radium, so as to give a discharge large compared with that 

 due to the natural ionization, the same value for (1) should 

 be found for the air mixed with emanation in this small tank, 

 as for the natural air in the large iron tank. 



The advantages of this method are due to the fact that the 

 measurements are all taken with the same electroscope, and 

 may be expressed in terms of scale-divisions of the same 

 instrument, which need not • even be disturbed from its 

 position. 



Now, in the actual experiment with the iron tank, 



d = 140 ; C 2 = 3-5 E.S. units. 



Y 1 = 2*17, Y 2 = 3*6 scale-divisions per minute. 



x 100 = 4-1. 



c 2 v 2 



This result is the mean of many experiments extended over 

 some months. 



The emanation from radium bromide was next blown into 

 a small tank of 80,000 c.c. capacity, and a similar series of 

 experiments were made. C^ was now equal to 21, and C 2 to 

 3'5, and the following values of these quantities were obtained 

 for various strengths of the emanation : — 



v 2 . 



V\. 





gjjxioa 



1-44 



4-4 





55 



093 



26 





6-0 



1-85 



63 





4-9 



1-32 



5-8 





4-4 







Mean.. 



52 



