Bumstead and Wheeler — Radio-active Gas. 



103 







Radium Emanation. 







Time in 



Observed 



Plotting 



Time in 



Observed 



Plotting 



minutes. 



ionization. 



Scale. 



minutes. 



ionization. 



Scale. 



3-0 



11-23 



52-9 



90*75 



20-28 



95-5 



8-1 



11-66 



54-9 



100-75 



20*17 



95-0 



12-75 



14-98 



70-5 



105-75 



21-18 



99-7 



16-75 



14-88 



70-1 



110-75 



21-68 



102-1 



20-75 



15-82 



74-5 



115-75 



21-12 



99-5 



25-75 



16-16 



76-1 



120*75 



21-12 



99-4 



30*75 



17-20 



81-0 



125-75 



20 92 



98-5. 



37-75 



16-87 



79-4 



135-75 



21-52 



101-3 



42-75 



17-68 



83-3 



145 75 



21-45 



101-0 



47-75 



17-70 



83-4 



205-75 



20-52 



96-6 



52-75 



18*05 



85-0 



220-75 



22-18 



104 5 



57-75 



18-58 



87-5 



268-75 



18-78 



88-4 



62-75 



18-88 



88-9 



278-75 



21-44^ 



101-0 "| 



69-75 



19-32 



91-0 



282-75 



21-25 ! 

 21-35 f 



ioo-o l 



100-5 [ 



76-75 



20-10 



94-7 



287-75 



82-75 



20-18 



95-0 



292-75 



20-92 J 



98-5 J 



The following values taken from the plotted curve will give 

 an idea of the agreement between the behavior of the two 



gases : 



Rise of Excited Activity. 



Time in minutes. Earth-Gas. Radium Emanation. 



20 74-6 74-4 



40 81-0 81-9 



60 86-6 87-9 



80 91-6 93-4 



100 96-0 97-5 



The earlier part of the curves in figs. 4 and 5 {t <20 min.) 

 can not be very accurate. It took about two minutes to intro- 

 duce the earth-gas, and to make the two experiments as nearly 

 alike as possible the same time was consumed in admitting the 

 radium emanation; the zero of the time scale in the carve is 

 the middle of this interval. Few observations could be taken 

 and the curve is so steep that small errors have a great effect 

 upon the point where the curve cuts the axis. Moreover, the 

 results of the diffusion experiment cannot be reconciled with 

 so small a value of the initial activity of the gas, as will be 

 seen ; and a special experiment in which radium emanation 

 was introduced rapidly indicated that the initial activity was 

 between 50 and 60 per cent of the final activity. But the 

 question could not be decided very positively with our appa- 

 ratus, since the slowness of the return of the needle to its zero 

 did not permit readings to be taken in very rapid succession. 



Diffusion through a Porous Plate. 



Figures 6 and 7 exhibit the results obtained when the bottom 

 plate was removed and the gas allowed to diffuse through the 



