RESIDUAL WATER NUCLEI. 



127 



In table 52 weak ionization is obtained by placing the radium tube 

 at 40 cm. from the fog chamber. The data, moreover, are investigated 

 by the new method of two sources of light 5 cm. apart, at a distance R 

 from the fog chamber. The number of nuclei n, computed for the 

 exhausted fog chamber, is corrected by multiplying by the volume 

 expansion v 1 /v = i . 25. Finally, b is computed from pairs of observations 

 about 20 seconds apart, as suggested by the brace. Water nuclei were 

 always precipitated before each test. In table 52 the exhaustion is 

 above the fog limit of air and the data are constructed in fig. 42 in com- 

 parison with cases for stronger radiation and of weaker radiation (by 

 decay) in table 51. Together they form a coherent series of curves, 

 since it is the number n present which determines the value of 6, no 

 matter whether the small number is due to low exhaustion (dp z /p near 

 the fog limit) ; or to decay of ions in the lapse of time (exhaustion / 

 seconds after removing the radium from the fog chamber), or due to 



TABLE 53. Decay of weak ionization. Radium at D = 40 cm. Bar. 76.9 cm.; temp. 

 i8.oC. ; <?/> 3 =2i .o cm.; dp^/p = o.2j2- Practically below fog limit of air. R = 

 cm. Exhaustion i . 25 =i> 1 /i>. 



1 Ions under radiation not lost by exhaustion like the rest. 



