5O CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



39. Radium within the fog chamber. Sealed tubes. An early series 

 of experiments on the observed distribution of ionization within the 

 chamber due to the presence of radium in different parts is given under 

 special treatment in table 17. Coronas from two sources of light were put 

 in contact, giving S. The radium was placed alternatively 12 cm. from 

 the two ends of the fog chamber, 45 cm. apart. The lines of sight, I near 

 the brass and II near the glass end, were 20 cm. apart in the middle of 

 the available length. 



TABLE 17. Radium within chamber. Tubes I-V. 

 25.7; airS=i.o; p 3 =2i,.o. 



Barometer 75.9; 

 =0.303. 



temperature 



* Fog chamber cleaned with 3 exhaustions. 



There was no vertical distribution of the ionizations, but the horizontal 

 distribution was as usual very evident. Assuming that the number of 

 ions produced per second, a, is given by a = 6w 2 -f-cw where 6= io~ 6 is the 

 decay constant and c = 0.036 an absorption constant. The values of a 

 are thus as follows: 



