2Iass of the Ions in the Electric Wind in Air. Ill 



necessarily taken by the surface they are approaching. The 

 curves for P and z are thus lowered by an unknown amount; 

 an amount which tends moreover to increase as the ring is 

 moved away from the point, but at a lessening rate, so that 

 the lowering becomes constant when z is considerable. It 

 is therefore from the higher parts only of the curves that 

 values of V may be obtained. 



In curves IV. specimens of the results obtained with the 

 final form of this apparatus are given ; each point being the 

 mean of four observations. The straightness of the curves is 

 unmistakable except for small values of z, where they all show 

 the effect of the alteration of p' just referred to. Fig. 3 

 shows the point which is taken as the zero of z. 



Curves IV. 

 (P) 



OYA/ES 







































9 b 



• 



S 











/ & 



s 

 / 











7 / 



* 













/ 



s 

 / 



M 



St* 





.-'* 







f s 



/ 

 s 



* 



r 









Jy 















O I 2 3 4- 5 6 Cm . (Z ) 



In all, three sizes of tube were experimented with. The 

 first, of internal diameter 1*28 centim., gave the rather low 

 values 



V+=342, V-=423. 



I mention these only because they appear in the Brit. Assoc. 

 Rep. for 1898 as the best values so far obtained. It has 



