Gases by the Motion of Negatively charged Ions. 203 



and 2, respectively. The forces X are given in volts pet- 

 centimetre [(potential of A) -f- (distance between the plates)]. 

 The unit of current is 1*410~ 13 amperes. The curves have 



Fig. 3.— Pressure 2-12 millim. 



160 240 320 400 480 



Volts per centimetre. 



ofif, 



640 



720 



not been traced back to the origin, as we are at present only 

 concerned with the connexion between current and electric 

 force when the potential- difference between the electrodes 



P2 



