i58 



VAPOR NUCLEI AND IONS. 



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respectively; or that an 

 inversion of Wood and 

 Campbell's results is a 

 question, since there is 

 usually incremented nu- 

 cleation in the afternoon 

 as compared with the 

 morning. This, however, 

 may be explained, if the 

 ions are large, even in 

 comparison with the 

 larger gradations of col- 

 loidal nuclei. Fewer of 

 these will therefore be 

 captured in proportion 

 as the ionization is 

 larger. Hence the figure 

 shows at a an apparent 

 corroboration of Wood 

 and Campbell's results; 

 at e an omission or in- 

 version of the periods. 

 But the e's are much 

 fewer in number, and in 

 comparison with the am- 

 plitude of the a 's, the e 's 

 are frequently neutral. 



In the second place, 

 the high nucleation dur- 

 ing the period of rain is 

 noteworthy. Here, then, 

 few ions were present. 

 As there is a modification 

 of the atmospheric po- 

 tential gradient during 

 this time, one might favor 

 an explanation on similar lines to the ideas suggested by Richardson.* 



100. Effect of the barometer. In the further development of the 

 investigation on the time variations of the efficient colloidal nucleation in 

 filtered air, the results are of the same character as those already dis- 



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* Nature, lxxiii, p. 607, 1906. 



