966 



Mr. S. Smith on Initial 



by collisions in the spaces S 1? S 2 , and S 3 . The total charge 

 on 2 is qo + q 2 - The terminals of electrodes 1 and 3 were 



joined, and — — — was measured experimentally. For this 



<?o + <?2 



purpose the method which is in common use in the laboratory 

 for measuring the ratio of two charges was adopted. The 

 arrangement is shown in fig. 3. 



Ffc. 3. 



A, B, and C are earthed cylindrical tubes, fitted with 

 ebonite plugs, to guard the leading wires from induction 

 effects. K L and K 2 are cylindrical condensers of equal 

 capacity, C. Q.E. is a Dolezalek electrometer, T a key 

 enabling the electrometer to be put into connexion with the 

 inside cylinder of either K x or K 2 . R a , R 2 , and R are 

 resistance-boxes, P a potentiometer, and S.B. a storage- 

 battery. 



The positive charge gained by the electrode 2 tends to 

 increase the potential of the inside cylinder of condenser K 1? 

 and this can be neutralized by bringing the outside cylinder 

 to a certain negative potential V. 



Then 



?o + ? 2 =-V.C. 



Also, by adjusting the ratio of the resistance R x to the re- 

 sistance R 2 , the inside cylinder of condenser K 2 can at the 

 same time be kept at zero potential. The cuter cylinder of 



K 2 is thus raised to potential 5 * . V; 



±t,-f±i 2 



hence 



9l + ?3= -R^V V ' 

 q -f y 2 Rj + R 2 



