52 Mr Purvis, The radiation of various spectral lines, etc. 



graphic plates, and the following table contains the numbers 

 obtained from the measurements of the separated constituents, 

 compared with those obtained by Rayleigh quoted by Lohmann 

 and by Lohmann himself. 



Eayleigh 



X^xH 



X 1013 



Lohmann 

 d\ 



X^xH 



X 10i». 



Purvis 

 d\ 

 ' X2 X 24,000 



X 10". 



Helium 



5875-618 



f - 4,09 s 

 i p 



I + 4,09 s 



-4,33 

 



+ 4,33 



-4,58 





 + 4,58 



Lohmann's were eye observations, and they might not be so 

 accurate as photographic ones. 



Furthermore, it may be that small variations in the amount 

 and nature of the constituents of the glass of the tubes produce 

 changes in the field between the magnetic poles ; and it is conceiv- 

 able that some of the energy would be absorbed by these con- 

 stituents, so that the full strength of the magnetic field would not 

 act upon the gaseous particles of the vibrating gas. This view 

 may explain the differences which have been noted in the 

 numbers obtained when the Zeeman phenomena have been ob- 

 served in gases. 



General Results. 



The results of these observations are : — 



(1) A comparison of the measurements of the constituents 

 of various divided lines of neon, helium and sodium observed with 

 an echelon grating by Lohmann and with a Rowland grating by 

 the author. 



(2) The important difficulty in distinguishing the real con- 

 stituents of a divided line from those of the adjacent images of 

 other orders when an echelon grating is used for the observations, 

 particularly when the line is divided into more than three con- 

 stituents. 



(3) The measurements of the shifts of the divided consti- 

 tuents of various neon lines towards the red end of the spectrum, 

 and that the shifts are different for different lines. 



(4) A comparison of the intensities of the normal undivided 

 lines of neon with those of Baly and Lohmann. 



I have to thank Professors Liveing and Sir James Dewar who 

 were good enough to lend me two tubes of neon used in these 

 experiments. 



