432 Mr Waran, On the effect of a magnetic field 



leaving the Balmer series lines unafiected brings about the se- 

 condary spectrum very prominently as shown in Fig. 4 (2). 



It is possible that the change in the spectrum is purely me- 

 chanical in origin. In Fig. 1 we saw that under the influence of the 

 magnetic field the discharge was deflected to either side. In each 

 of these streams the electrons being much more easily deflected 

 out of their path than the positive ions, they might be going in a 

 layer much closer to the walls than the positive ions as shown in 

 Fig. 1. In such a case we may regard the massive positive particles 

 as bombarding the layer of electrons adjacent to the walls, thus 

 giving rise to mechanical and electrical reactions that cause a 

 peculiar excitation of their spectra. Orbits and frequencies pre- 

 viously not natural might then become possible and this would 

 account for the change observed. 



The spectrum of hydrogen with its simple structure is only 

 very slightly susceptible to the influence of the field, excepting of 

 course the secondary spectrum which it brings about. When the 

 gas is pure and at a low pressure the Balmer series lines undergo 

 very little change in their intensity. But when it is present mixed 

 with other gases or at higher pressures it is brought out intensely 

 by the field though not prominent without it. From our observa- 

 tion of the enhancement of the lines of the monatomic gases, now 

 confirmed independently by the study of Messrs Kent and Frye 

 on Argon, if we are to attribute it to the enhancing efi^ect of the 

 magnetic field on the atoms, this would mean that at higher 

 pressures atoms predominate giving the Balmer series, while at 

 lower pressures the molecules predominate giving the secondary 

 spectrum, a conclusion in accordance with that arrived at by 

 G. P. Thomson in his study of the spectrum of the hydrogen 

 positive rays. The effect of the field in enhancing the secondary 

 spectrum shows however that this division of share in the radiation 

 is by no means clear cut between the atom and the molecule. 



From the enhancement of the Balmer series lines observable 

 at higher pressures it is possible that the atoms are mainly respon- 

 sible for them and by the employment of a magnetic field in con- 

 junction with Prof. Wood's| long discharge tube the lines of the 

 Balmer series obtainable in the laboratory could probably be still 

 further increased. 



Experimenting with nitrogen having a constitution and spec- 

 trum considerably more complex than hydrogen the effects ob- 

 served are very complicated. When a condensed spark is not 

 employed to excite the tube, the effect of the field is to enhance 

 the band spectrum and to bring in some of the lines belonging to 

 the line spectrum of nitrogen with a different intensity distribution 



* G. P. Thomson, Phil. Mag. vol. 40 (1920), p. 240. 

 t R. W. Wood, Proc. Roy. Soc. A, vol. 97, p. 455. 



