CHAPTEE II 



IONIZATION BY POSITIVE IONS 



17. Conductivity between parallel plates when positive 

 and negative ions generate others by collisions. 



The effects produced by the motion of positive ions 

 may be deduced from determinations of the currents 

 that pass between parallel plates while ultra-violet light 

 is falling on the negative electrode, if the forces and the 

 distances between the plates are sufficiently large. 



It has already been shown that when X/p and I are 

 small, and I is varied whilst X and p are kept constant, 

 the number of negative ions reaching the positive 



electrode is w e a , where a is a constant depending 

 on X and p. For large values of X/p and I the number 

 of negative ions reaching the positive electrode is 



greater than n e a , showing that some other form of 

 ionization has come into play. This stage is attained 

 even when the potential between the plates is much less 

 than that required to produce a spark. It will be seen 

 from the following investigations that all the features of 

 the new process of ionization can be explained on the 

 supposition that it arises from the action of the positive 

 ions. 



Further, it is obvious that if both positive and negative 

 ions produce others in sufficient numbers, a current 

 would be obtained which would last after the supply 



