C. Barns — Nuclei and Ions in Dust-free Air. 141 



son with water vapor show. It is a little difficult to under- 

 stand why the ionized nuclei in alcohol vapor should, like the 

 colloidal nuclei, be larger than the corresponding cases for 

 water vapor, unless the ions are aggregated colloidal nuclei, a 

 point of view tentatively advanced elsewhere.* 



6. Data for alcohol vapor. — The behavior of alcohol 

 vapor is shown in the usual way in the following chart, fig. 2, 

 where 8p is the sudden fall in pressure from normal atmos- 

 pheric pressure, producing the corona of the angular diameter 



1400 

















1 

































S^ 





















* 



ju«y 



















800 













v 



















600 







o / 







f* 



> 

















400 









3 



of 







x-i 



vr____- 















n*ic 3 









jb o 









<$¥ 



w 







<s/ 





Ls? 



-^o ,-, 





o 









*y 













1Z 14 16 18 ZO ZZ 24 26 



30 3Z W 36 3» 



s I 30, when the eye and the source of light are at distances 40 

 and 250 cm on the opposed sides of the fog chamber. The 

 nucleation n deduced from s is computed in the way given 

 above, §4, and indicates the number of nuclei in the exhausted 

 fog chamber. It is assumed therefore that the nuclei are re- 

 produced more quickly than they can be withdrawn by the 

 exhaustion. Measurement of s is not very satisfactory, as the 

 coronas are blurred and accompanied by dense fogs and 

 change rapidly on subsidence. The effect of X-radiation leads 

 to the same terminal corona which appears for the non-energized 

 vapor. 



The results as exhibited in fig. 2 are seen in connection with 

 earlier results for media of water-air and water-carbon-dioxide, 

 the same condensation apparatus and method underlying all 

 experiments. One may notice at once that in the cases C0 2 - 

 water and air-water, both for the non-energized and for the 

 energized state, the observed data would be obtained by shift- 

 ing the air-water diagram as a whole to the right, as if the 

 cooling in case of C0 2 -water vapor were less efficient, f The 



♦This Journal, xx, 1905, p. 453 ; Phys. Keview, xxii, 1906, p. 109. 

 f Phys. Keview, April, p. 252, August, 1906. 



