for Production of Luminosity in Atmospheric Neon. 929 



This increase of luminosity was accompanied by the appear- 

 ance o£ the remaining red and orange lines of Table I., which 

 had previously been of too small an intensity to be visible; 

 but the lines of Table III. and, in fact, all the lines belonging 

 to subordinate series were absent. The curve shows that after 

 the large increase of ionization, prob ibly caused by a sudden 

 neutralization of the space charge near the filament, the 

 current increased steadily with increasing electron velocity 

 until 23'4 volts, after which it began to increase at a more 

 rapid rate. At the stage where this more rapid increase 



Fig. 2. 













C 



urve A. 







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u 



I 









3 









or-*' 















1 















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z 

























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r c 

















z 



5 



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2 



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Curve B. 



Electron velocity, volts Electron velocity, volts 



began the brighter green lines given in Table III. suddenly 

 flashed out, and as the electron velocity was still further 

 increased the remaining subordinate series lines of Table I. 

 gradually made their appearance. The curve B of fig. 2 gives 

 the values of the ionization current corresponding to different 

 values of the electron velocity as this was gradually reduced 

 from about 27 volts. At 23*2 volts, in this curve, the last 

 remaining subordinate series lines suddenly disappeared, the 

 others having gradually faded out earlier as the election 

 velocity was reduced. After this point the current decreased 

 less rapidly as the velocity was reduced until 21*1 volts, when 



