426 Mr. E. Rutherford on the Velocity and Rate 



intervals after the cessation of the radiation a large E.M.F. 

 was applied to the outside coating of the bell-jar and the 

 quantity of electricity which was given up to the central 

 electrode was determined. 



A pendulum interrupter was used to break the battery- 

 circuit and to apply the E.M.F. at varying intervals. A 

 heavy iron ball was suspended by a wire 315 cm. long, and 

 the contacts were broken by a rod fixed to the bottom of the 

 ball. 



Fig. 2 represents the arrangement of the experiment. The 

 induction-coil primary circuit was completed through the 

 brass lever AB, which pressed against a copper support C. 



Fi<?. 2. 





D Path <* 



~ fendulum. 



-o- 



When the pendulum struck the lever AB was knocked away 

 from C and the current broken. In order to apply a high 

 E.M.F. at a definite instant, recourse was had to a shunt 

 method which worked very well An practice. A battery of 

 one hundred small accumulators nad one pole connected to 

 earth and the other pole through a high carbon resistance R 

 to the copper support E. A wire passed from E to the tin- 

 foil on the outside of the conducting vessel H. The lever 

 DF, which was kept pressed against E by a spring, was 

 connected to a good earth. When the lever was in position, 

 therefore, the vessel H was very nearly at zero potential, for 

 the resistance of the lever DF and the earth connexions was 

 very small compared with the carbon resistance R. When 

 the pendulum struck the lever DF the earth connexion was 

 broken and the vessel H was immediately charged up to the 

 potential of the battery. By altering the distance between 

 the two levers the time between breaking the battery current 

 and applying the E.M.F. could be varied within limits. 



