Conducting Gases on the Direction of the Electric Field. 213 



plate D broken after a definite interval by two keys operated 

 at a distance. 



The following results were obtained on the difference 

 between the positive and negative currents with variation o£ 

 potential-difference between the plates. 



Diameter of centre plate D 7 centims. Air dried over 

 P 3 5 for one day. 





Cur 



•ent. 





P.D. between 

 Plates in volts. 







Eatio between 

 Currents. 









Lower Plate-j-. 



Lower Plate — . 





6 



1 



110 



1-10 



12 



21 



2-5 



1-20 



26 



49 



6-2 



1-26 



53 



12-5 



158 



1-27 



104 



817 



41-7 



1-32 



157 



547 



704 



1-29 



211 



84-7 



109 



1-29 



310 



130 



157 



1-21 



460 



171 



190 



111 



610 



190 



200 



108 



Each division of arbitrary scale is 2*3 10 ~ 12 amperes. The 

 results are plotted graphically in fig. 1 a (p. 214), where the 

 ordinates represent current and abscissae volts. 



It will be observed that the current when the lower plate 

 is negative is always greater than when it is positive. The 

 maximum ratio observed is 1*32 for 104 volts. Another 

 peculiarity is that the current increases much faster than the 

 potential-difference. For an increase of P.D. of 4 times 

 Irom 26 to 104 volts, the currents increase 6*7 times and 

 6*5 times respectively. When the plates were brought closer 

 together, the same general results were obtained for low 

 voltages ; but the currents approached to approximate 

 equality sooner for the high voltages. For example, with 

 the plates centims. apart, the ratio of currents was 1*20 for 

 27 volts, but for 300 volts the currents were nearly equal. 



In this case most of the ions are produced near the lower 

 plate, and are then separated by the electric field. In con- 

 sequence of this, when the current is passing, nearly all the 

 ions near the upper plate are of one sign. 



A special experiment, after the manner described in a 

 previous paper *, showed that the intensity of the ionization 

 rapidly diminished from the surface of the radio-active plate. 



* E. Rutherford, Phil. Miff. Jan. 1899. 



