for Production oj Luminosity in Atmospheric Neon. 927 



first produced in the gas were those given in the table 

 ■below. 



Table II. 



The brightest lines in the spectrum of the luminosity 

 first produced. 



X. 



Series. 



6402 



l-5,H-2,-p 9 



6143 



1-5, s 5 -2,p 6 



6096 



1-5, s 4 -^2,p 4 



6074 



1-5, «i-2, p 3 



5915 



15, s 5 -2, p 4 



5852 



l'5,s 2 -2, Pl 



5401 



1-5, s 4 — 2, p, 



With suitable values of the intensity of the electron 

 stream and gas pressure, slight differences in the minimum 

 voltages at which these bright lines first became visible 

 were detectedc In these cases the line X 5852 was the 

 first to appear, and then the lines of higher wave-length in 

 the table, and finally X 5401 ; but the minimum electron 

 velocities at which X 5852 and X 5401 were ever observed 

 did not differ by more than 0'3 volt. With an intense 

 electron stream, all the lines in Table I. of longer wave- 

 length than X 5852, and also the line X 5401, could be 

 identified in the spectrum of the glow a few tenths of a 

 volt after it was first produced, and it was found that the 

 visibility of these lines of higher wave-length than X 5852 

 depended solely upon the general brightness of the lumi- 

 nosity produced in the gas. From Table I. it may be 

 seen that all these lines have been classified by Paschen 

 as belonging to sequences of the type (1*5, s — m, p)\ i. e., 

 they are principal series lines. It was therefore concluded 

 that the spectrum of the glow produced at 20 volts contained 

 all the principal series lines of Table I., the slight differences 

 In the minimum electron velocities at which different lines 

 w r ere first observed being due entirely to the relative intensities 

 of the different lines. 



As the speed of the electrons was further raised about 

 2 volts or more, certain lines in the blue, green, and yellow, 

 of which those given in Table III. were the brightest, suddenly 

 made their appearance. 



3P 2 



