x] RADIO-ACTIVE PROCESSES 299 
shown in Curve 4, Fig. 57 (with the observed points marked, for 
comparison). The curve B shows the theoretical curve of the decay 
of the activity of Th X and the emanation, supposing there is no 
secondary change into emanation X. Curve C shows the differ- 
ence curve between the curves A and B, ve. the proportion of the 
activity at different times due to the emanation X. The activity 
due to emanation X thus rises to a maximum about two days after 
removal of the Th X, and then decays with the time at the same 







Intensity of Radiation 
a 
° 
- 
fe} 







Time in Days. 
Fig. 57. 
rate as the Th X itself, z.e. the activity falls to half amount every 
four days. When the value of t exceeds four days, the value of 
e-“—)t in the theoretical equation is very small. 
The equation of decay is thus expressed by 
Tiga KX, NE 
polite es 
v.e. the curve decays in an exponential law with the time. 
