/>// ///(' Motion of Posif'u'C Ions in <( (r((..^. 51)9 



Bv th<' action of tlio liolit a certain nnml)or, n^^, of neo-ativc 

 ions arc set free, which o(Micrato others in their passao-e 

 through the gas. If the j)ressnr(^ p and ehn-tric force X are 



constant, then for the snialh>r vahi(»s of and distances 



between the ])hites a, the number of negative ions reaching 

 the positive electrode is ?i^e«". The (piantity oc, depends on 

 the pressure and the electric force and denotes the number 

 of ions that a single negative ion generates in moving through 

 a centimetre of the gas. 



For la roe values of ~— and a the number of neoative ions 

 P ' 



reaching the positive electrode is greater than n^e"''^, showing 

 that some other form of ionization has come into play. This 

 stage is attained even when the potential between the plates 

 is much lower than that required to produce a continuous 

 discharge. 



It will be seen from the following investigations that all 

 the features of the new^ process of ionization which is intro- 

 duced can be explained on the supposition that it arises from 

 the action of the positive ions. 



It is obvious that if both positive and negative ions give 

 rise to others by collision in sufficient numbers we would get 

 a continuous discharge. The investioations show how the 

 potential required to produce a continuous discharge may be 

 found on this theory, assuming that all the ionization is 

 produced by collisions of positive and negative ions with 

 neutral molecules in a uniform field of force. There is a 

 very accurate agreement between the potentials thus cal- 

 culated and the sparking potentials determined experi- 

 mentally. 



2. An investigation of the currents which would be pro- 

 duced between parallel plates, when both positive and negative 

 ions generate others by collision, will show^ what experiments 

 would be most suitable in order to test the theory. 



If a number rq of negative ions start from the negative 

 plate and move through a distance a to the positive plate 

 they will generate others in the gas, and a number ^iQe"-"- will 

 reach the positive plate. The positive ions (%(€"" — 1) in 

 num])er) produced in the gas will move in the opposite 

 direction, and let it be supposed that these also have the 

 property of ionizing the gas. 



The results of the experiments may here be anticij^ated 

 and it may be assumed that the positive and negative ions 

 produced by the impact of a positive ion with a neutral 

 molecule are identical with the positive and negative ions 



2 Hi 



