26 



CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



now no reason referable to causes within the fog chamber, unless there 

 exists a singularly marked temperature effect, presently to be investi- 

 gated. Series VI alone is peculiar, showing a strong initial tendency to 

 return to the earlier set, III to V. Water nuclei were precipitated 

 before each observation. The data for n 335 are also inscribed in fig. 8a 

 and fig. 86, where they are compared with the barometer and the tem- 

 perature of the fog chamber in a general way. 



Table n also contains the corresponding values of dp/p and the 

 nucleations n derived from the new investigations in Chapter IV. From 

 these the values w -0 for 



and n _ S45 for 



are 



derived to be used in the correlative summary in sec. 20. The nucleations, 

 w o.345> which suffice for the purpose, are given with the others in figs. 8a 

 and 86. 



is cm. 



30 



VTfo. 



5/14345 



100 



50 







27 Stpt. Z9 1 Oct. 3 S 1 9 11 13 If 11 



FIG. 8b. Changes of vapor nucleation of dust-free air, barometric pressure, and 

 temperature of the fog chamber in the lapse of time. 



The data for n 335 in figs. 8a and 86 sometimes follow the barometer, 

 sometimes depart widely from it; but coincidence will usually occur only 

 when both accompany the same temperature effect. As a rule there is a 

 rise of nucleation from morning to afternoon, suggesting the phenome- 

 non due to external radiation discovered by Wood and Campbell (section 

 i ) , but in these cases temperature is also apt to rise coincidently . The rise 

 in question fails to occur but 4 times out of the 13 observed in August, 

 but 7 times out of the 24 observed in September (2 being neutral), and 

 but 5 times out of the 13 observed in October. 



