﻿Nature of the Large Ions in the Air. 



519 



entry in the table, so the estimated value, 1253, of the 

 reciprocal of the mobility for a humidity of 4 per cent, may 

 be too large. 



As a determination of mobility requires the measurement 

 of a series of ionization currents, the investigation is a tedious 

 one in the case of the natural large ions where the ionization 

 is not under control and is subject to considerable variations. 

 The values given in Table I. represent the results of observa- 

 tions on the few occasions, during two and a half years or 

 more, when the ionization was sufficiently constant in this 

 laboratory for the purpose of the calculation. Under the con- 

 ditions a very exact comparison of the theoretical deduction 

 with observation is not possible. 



It can be said at once, however, that the observations 

 show that X/A/, or n in the reduction formula, must be very 

 nearly equal to unity, and on the assumption that it is so, 

 the pressures corresponding to the mobilities in Table I. 

 have been reduced to a common temperature of 20° C, and 

 are entered in the table. 



Fia-. 1. 



? 



S 



i 



Zp/O 



b 





— — 













__ 





■ So'fUro 



Von- - 









/ 















/ 



/> 



i 













/ + 

 + 















/ 















/ 















/ 



/ 















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1 



O tOOO 2000 5000 4000 



Reciprocal of Mob! My 20° C. 

 From these reduced observations fig. 1 lias been drawn: 

 the curve therefore shows the relation between the reciproca 



