50 



Mr Purvis, The radiation of various spectral 



lines ; and these differences eliminate any sources of error caused 

 by a movement of the instrument. If there had been any such 

 movement, it is obvious that the shifts would have been equal. 



There was a considerable increase in the luminosity of the neon 

 when it was vibrating in the magnetic field ; and although the 

 times of exposure and the other conditions were the same, the 

 intensities of the unaltered lines when the gas was vibrating 

 normally were weaker than the strongest constituents when they 

 were divided. And in no case was the sharpness of the constituents 

 equal to that of the unaffected lines, so that there was always 

 some difficulty in measuring any shifts or separations. 



With regard to the intensities of the normal undivided neon 

 lines it may be mentioned that my observations do not coincide 

 exactly with those of Baly* or Lohmann, as the following table 

 shows. But not much importance can be attached to observa- 

 tions of this kind, unless the differences are clearly marked ; and 

 possible variations in the efficiency of the dyed emulsion in various 

 parts of the photographic plates should not be left out of con- 

 sideration, although there are some differences which may indicate 

 the influence of varying conditions of pressure and discharge in 

 the tubes, as for example, in 5852 and 6717. 



-The spectra of Neon, Krypton and Xenon," Phil. Trans. A. 202, 1904, p. 183. 



