SIVCKSSION 



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195 



large to be measured by means of a sensitive high-resistance galvanometer, and 

 readings were taken as quickly as possible after removal of the platinum from the 

 emanation vessel. The initial value of the current (taken as 100) was deduced by 

 continuing the curves backwards to meet the vertical axis (see fig. 12), and was found 

 to be 3 X 10~ 8 ampere. 



These results are shown graphically in the upper curve of fig. 12. The initial 

 rapid decrease is due to the decay of the activity of the matter A. If the slope of 

 the curve is produced backwards from a time 20 minutes after removal, it cuts the 

 vertical axis at about 50. The difference between the ordinates of the curves A+B-f-C 

 and LL at any time is shown in the curve AA. The curve AA represents the activity 

 at any time supplied by the change in radium A. The curve LL starting from the 

 vertical axis is identical with the curve already considered, representing the decay of 

 activity measured by the ft rays for a long exposure (see fig. 6). This is shown by the 

 agreement of the numbers in the following tables. The first column in the table below 

 gives the theoretical values of the activity deduced from the equation 



L 



X 3 



for the values of X.,, \^ previously employed. The second column gives the observed 

 values of the activity deduced from the decay curve LL. 



2 c 2 



