216 Prof, Rutherford on Dependence of the Current through 



Fig-. 2. 



Earth 



Earth 



method was found in practice to be rapid and accurate. The 

 following are results obtained for different voltages : — 



Distance between plates 10*5 centims. Upper plate charged, 

 lower plate earthed. 



Distance in cms. 



from Lower 



Plate. 



Upper Plate 



Upper Plate 



Upper Plate 



Upper Plate 



107 volts -f . 



107 volts -. 



214 -f. 



214—. 



1 



1-55 



•91 



4-50 



244 



2 



332 



2-14 



903 



5-84 



3 



601 



4-20 



161 



120 



4 



9-79 



7-11 



26-2 



223 



5 



16-8 



15-3 



414 



38 6 



6 



27-0 



251 



67-8 



631 



7 



41-2 



401 



995 



97-3 



8 



59-4 



58-3 



131 



127 



9 



76-5 



76-0 



167 



164 



The ratio of the two currents through the gas was 1*27 

 for 107 volts, and 1-20 for 214 volts. 



Fig. 2 a shows the results graphically. 



It will be observed that the potential-gradient, near the 

 radio-active surface, is very small compared with that near 

 the upper plate, and that, near the upper plate, the potential- 

 gradients are very nearly the same whether the top plate is 



positive or 



The potential-gradient near the lower 



