l 54 



VAPOR NUCLEI AND IONS. 



the fluctuations of positive and negative ionization in successive obser- 

 vations, on the same or on succeeding days, usually show the same sign, 

 although not the same absolute value, this is not in general the case 

 with the monthly ionizations. The two curves of fig. 62 throughout the 

 greater part of their course vary in opposite directions. 



Table 53. Mean monthly ionizations, 

 corresponding to table 51. 



Compared with the uniform curve for nucleation the appearance of 

 the ionization curve is sufficiently distinctive. One might perhaps be 

 inclined to refer the dip in the negative curve between November and 

 February to the more marked "absorption" of the negative ions by the 

 increasing nucleation. But the two curves are not sufficiently similar 

 and there is no reason why the absorbed ion should fail to have a record 

 in the condenser. The only conclusion to be drawn from the results 

 for the distribution of either the positive or the negative ions is this, 

 that there is no discernible relation between the number of ions and 

 the number of Aitken nuclei present in the atmosphere at any time, or 

 that the two distributions result from entirely distinct causes. The 

 ionization of a given region is independent of artificial local contribu- 

 tions, however abundant these may be. 



