36 NUCLEATION OF THE UNCONTAMINATED ATMOSPHERE. 



The fog limit of filtered air after the radium is withdrawn soon 

 regains its original value; but some definite time (say 15 minutes) is 

 necessary even here. It does not seem to vary appreciably with the 

 time of exposure. (See figs. 31, 32.) 



As the radium of low power (10,000 X) is inclosed in glass 0.04 

 cm. thick, it is probable that /? and y rays are chiefly responsible for 

 the nucleation. Hence it appears that nuclei are produced by suffi- 

 ciently swift moving corpuscles as well as by the X-rays, an important 

 result bearing on an inquiry suggested above. This will be further 

 substantiated in the next chapter in favor of the gamma rays. 



-A 



{wlffn, Seoty 



STX. 



25 26 



FIGS. 33-34. Apertures 

 of coronas (5) and nuclea- 

 tions (n) varying with the 

 pressure differences (5/), 

 for the case of dust-free 

 air energized by radium 

 acting from different dis- 

 tances. 



FIGS. 35-37. Decay 

 curves found after the re- 

 moval of the radium from 

 the fog chamber. 



Table n, referred to iii fig. 

 33, will be fouud as table 20, 

 P- 37. 



Table 12, referred to in fig. 

 35, will be found as table 21, 

 P. 3S. 



Table I2a, referred to in fig. 

 37, will be found as table 22, 

 p. 40. 



33. Data for nucleation. The results for nucleation in case of a 

 dust-free atmosphere energized by radium (io,oooX) contained in a 

 hermetically sealed glass tube are clearest in the third part of table 

 1 8, where nearly straight w-curves for inferior and superior coronas 

 may be made out (fig. 28). Part 2, containing data obtained shortly 



