56 



THE THEORY OF IONIZATION OF GASES 



a and (3 having been found in terms of X and p by 

 the methods that have been described. 



The plates were then set at the exact distances apart S, 

 and the potential V required to produce a spark was 

 determined. The results of the experiments 1 made with 

 air, hydrogen, nitrogen, carbon dioxide, argon, and helium 

 are given in Tables XVL, XVII., XVIII., XIX., XX., and 

 XXI., and they show the close agreement that exists 

 between the theoretical sparking potential SX and the 

 sparking potential V determined experimentally. The 

 product of the pressure p and distance S is given 

 in the last column of each table to illustrate Paschen's 

 law. 



TABLE XVI. 



Am. Sparking Potentials. 



1 The sparking potentials for air and hydrogen are taken from 

 the papers by the author, Philosophical Magazine, November, 1903, 

 and by the author and Mr. Hurst, Philosophical Magazine, 

 December, 1904 ; those for carbon dioxide and nitrogen are taken 

 from the paper by Mr. Hurst, Philosophical Magazine, April, 1906 ; 

 and those for argon and helium from the paper by Messrs. E. W. B. 

 Gill and F. B. Pidduck, Philosophical Magazine, August, 1908. 



