CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



I conclude, therefore, that by far the greater part of the dependence 

 of the vapor nucleation upon the barometer is the necessary result of 

 the thermodynamics of the case, but that conclusive evidence of the 

 absence of other causes either within or without the fog chamber on the 

 time variation of its nucleation, though extremely difficult to make out, 

 seems as yet to be outstanding. 



15. New data for vapor nucleation in the lapse of time. In table 10 

 results of the same character as the preceding have been collected. 

 Moreover, by choosing a particular dp (n n^) I (p ?0 =0.320 and 

 reducing all data for n to this value, the result so found (w 0-320 X io~ 3 ) 

 should be independent of atmospheric pressure, etc., and respond to 

 external radiation if such exists. The data are shown in fig. 8a. They 

 are not out of keeping with Wood and Campbell's phenomena as a whole, 

 but they do not follow the barometer. The correction of n is about i . 7 

 per o.ooi of the pressure ratio, but it is too uncertain in this region, 

 since the graphs are of pronounced curvature. 



TABLE 10. Time variation of the larger colloidal nucleation of wet dust-free air. 

 Conical filter. Apparatus II with 2-inch pipes, cleaned by precipitation before 

 observation. p m = o.i; p = P p m ', p p 2 =I 9-9- 



1 Not cleaned by precipitation. 



Hence in table n a larger fiducial value (dp [TT x 1 ])/(pi:') =0.335 

 was selected in turn, as the graphs in this part of the field (see arrow in 

 fig. 7) are more nearly straight. At the outset complete series of results 

 (August 10, n, and 12) were investigated; subsequently but three 

 observations in the neighborhood of the abscissa 0.335 fully sufficed. 

 The completed graphs are given in fig. 7 and marked VI to X. Their 

 position is throughout low as compared with III to V, for which there is 



