222 Prof. Rutherford on Dependence of the Current through 



Fig. 3. 



Earth 



Earth 



Plates 10 centims. apart. Mean width of stratum 1 centim. 



P.D. in volts. 



Current. 



Eatio of the 

 Currents. 



Plate A+. 



Plate A—. 



32-5 



58 

 115 



•63 



1-84 

 5-7 



•82 

 2-35 

 64 



1-30 

 1-28 

 1-12 



Further data of this experiment are given in a later calcu- 

 lation (pp. 226, 227). 



The same general results are here observed as in the case 

 of ionization produced by a radio-active substance. The 

 current with the plate A negative is greater than with the 

 plate A positive. It will also be observed that the current 

 increases very much more rapidly than the P.D. For an 

 increase of the voltage of 3*5 times the current with A positive 

 increases nearly 9 times, and with the plate A negative nearly 

 8 times ; i. e., the current is more nearly proportional to the 

 square of the P.D. than directly proportional to it. A general 

 explanation of these results can readily be given when the 

 movement of charged ions between the plates is considered. 

 Imagine a thin stratum of rays producing very powerful 





