396 Prof. J. J. Thomson and Mr. Rutherford on the Passage 



The experiments show that the effect of the distance between 

 the electrodes (two parallel plates) on the current is very 

 marked. The following tables show the result of some expe- 

 riments on this point. 



Potential- Difference between Electrodes 60 volts. 



Distance between electrodes, Current (arbitrary 



in millimetres. scale.) 



•1 9 



•12 15 



•25 21 



•5 37 



1 50 



1-5 62 



3 91 



8 110 



With this large potential-difference the current was satu- 

 rated in all the experiments. 



The next table contains measurements with a small potential- 

 difference. 



Potential-Difference between Electrodes 1*3 volt. 



Distance between electrodes, Current (arbitrary 



in millimetres. scale). 



•25 10 



•75 32 



2 ...... 48 



3 53 



8 53 



18 40 



In this case the effect of distance is not so well marked as 

 in the previous one, where the E.M.F. was sufficient to satu- 

 rate the current at all distances. 



The measurement of the rate of leak when the current is 

 saturated enables us to form an estimate of the number of 

 conducting particles present in the gas ; as in this case the 

 number of conducting particles produced in unit time by the 

 rays is equal to the quantity of the electrolyte destroyed by 

 the current in the same time. Let us take the case of hydro- 

 gen ; when the current was saturated, the rate of leak between 

 two plates each about 10 sq. cm. in area and 1 cm. apart 

 was about 1 volt per second when a capacity of about 30 cm. 

 was in connexion with the electrometer. Thus the quantity 

 of electricity passing between the plates in 1 second was 



