AIR ENERGIZED BY RADIUM. 



33 



dicity here (figs. 27, 28), and show a high fog limit at about 8/> = 2 

 the coronas at 8/ = 24.y being just appreciable. The reason for the 

 raised fog limit (air freer from dust) is not apparent ; but the volume 

 ratio of fog and vacuum chambers is here 8/> 0.13. 



The immediate effect of introducing radium is seen in the second 

 part of the table, at first without periodicity, and the fog limit is at 

 once reduced to 8p = 19 cm. (figs. 27, 28). 



TABLE 18. Effect of radium immediately after insertion. Long condensation cham- 

 ber, v 11,000 cm. 3 ; v\V=o. 13. Temperature, 26 C. Plug valve. Goniometer 

 close to apparatus. 



* Periodicity. 



1^=150,000; ratio 1.5 Njn. 



Nucleation, 75 minutes after the first observations, has much in- 

 creased (c<zt. par.); but direct comparison is not possible, because 

 the latter data are now distinctly periodic, and an upper and a lower 

 curve of apertures has appeared, without appreciably displacing the 

 fog limit. After further 135 minutes, the upper limit has probably 

 reached a stationary value (figs. 27, 28). 



In the last part of the table the periodicity of aperture, s, for air in 

 the presence of radium, is specially investigated for 8/> = 24.8 cm. 

 Exceptionally high superior values of s are again followed by excep- 

 tionally high inferior values (fig. 26), while exceptionally low inferior 



