AIR ENERGIZED BY RADIUM. 



35 



In table 19 the same effects are studied after the radium was in the 

 apparatus for over 24 hours. The data in the outgoing series (8/> 

 increasing) are distinctly periodic, until the highest value 8/> = 28.i cm. 

 is reached, which seems to wipe out the periodicity for the returning 

 series (figs. 29, 30). Curiously enough, the fog limit has apparently 

 risen, being now 8/> = 20 cm., instead of 19, as in table 18. If all results 

 be compared at about 8f> 25 for mean values of s, they show for- 



(no periods) 



(periods, s == 30 52) 



(periods, 27 62) 



16 



23 

 32 



Air (no exposure), 5 = 1.4 



Radium, short exposure, 3.6 



exposure, 2 hours, 4.1 



exposure, 24 hours, 4.5 



Air (20 minutes after removing radium), 1.4 



Long exposure to radium has increased the amplitude of the variation 

 of aperture, s. The limiting maxima for high values of 8fi in the 

 case of radium are in excess of the corresponding values for air. 



TABLE 19. Effect of radium left in apparatus 24 hours (23 C.) 



removed. 



and thereafter 



* Periodicity even in the absence of coronas. f Periodicity ceases. \ Returning. 



32. Remarks on the tables. The inference has already been drawn 

 that the number of nuclei as well as their size varies as the ionization 

 per cubic centimeter. The fog limit is reduced by the presence of 

 weak radium in sealed thin glass tubes within the chamber, from 

 8/> = 24 to 19 cm., observations which may be made pretty sharply. 

 This implies (quite apart from number) that the nuclei in the pres- 

 ence of radium are larger, as they are the offspring of a more highly 

 ionized field than exists in nonenergized identically filtered air. But 

 apart from the fog limit, the number of nuclei large enough to fall 

 within the scope of any given Sp is correspondingly increased. 



