72 



Dr. S. J. Plimpton on the Recombination of 



closed^ so that the charge received on B may be measured 

 by the electrometer. 



By taking a series of readings in this way with the key 

 at different positions along the path of the pendulum, the 

 relative numbers of ions remaining in the gas after definite 

 intervals of time was obtained directly. Throughout the 

 experiment, readings were frequently repeated with the 

 key F in such a position that the field was applied before 

 the flash occurred in order to detect any lack of uniformity 

 in the action of the apparatus. 



Calibration of Pendulum. 



In order to ascertain the time intervals during which the 

 ions ^ were allowed to re-combine when the switch which 

 applied the field to the gas was placed at various positions 

 along the path of the pendulum, the following method was 

 used : — 



The switches S and F which applied the X-ray flash and 

 the field respectively, were connected as shown in fig. 2. 



Fiff. 2. 



CI ID 



-a a 



£" 



I 



W 



Both switches were initially closed and the double pole- 

 switch A was closed at CD, putting a standard condenser 

 B in series with the switches § and F. The pendulum was 

 then released, opening the switch S, and thus permitting a 

 storage-cell E to charge the condenser through a known 

 high resistance, R. The charging continued until the 

 pendulum opened the switch F which breaks the charging 

 circuit. The condenser was then allowed to discharge 

 through a galvanometer by closing the double throw- 

 switch A in the opposite direction. 



The time required by the pendulum to swing from the 



