158 



Physics. — Magnetic ?'esoIution of spectrum lines and temperature. 

 by H. R. Wo]-TJER and Prof. P. Zeeman. 



An influence of the temperature of the source of light on the 

 magnitude of magnetic separation till now has been vainly sought. 

 There seems to be a possibility for such an influence, due to the 

 free electrons in the source of light, if we accept Ritz's theory of 

 magnetic resolution, at least in its original form. We thought it of 

 interest to inquire for such an action, now that we are able to 

 produce narrow spectrum lines of low temperature by means of the 

 small tubes of Wood and Zeeman ^). On the other hand we possess 

 sources of light of very high temperature, viz. the oxygen-acetylene 

 flame and the electric spark. 



With these means for the magnetised source of light, Mr. H. R. 

 WoLTJER has made an investigation concerning magnetic resolution 

 at different temperatures. An exhaustive discussion only of the 

 results of the measurements, which shall be published in H. R. 

 Woltjer's thesis for ihe doctorate, can fix the maximum change of 

 the magnetic resolution. Besides, the magnitude of the resolution 

 the ratio of the intensities of the divided components is of 

 importance to theory. We have begun a separate investigation con- 

 cerning this subject. In the first place the behaviour of the line D^ 

 was investigated. Under the influence of the magnetic field it is 

 resolved into six components, of which four vibrate at right angles 

 to the field and therefore under the same circumstances as to pola- 

 risation. The polarising action of the grating ^) and of the glass 

 sodium tube cannot change therefore the ratio of the intensities of 

 these four components. The reproduction in fig. 2 shows the outer 

 components of the magnetised absorption sodium-lines using one of 

 the above mentioned tubes (temperature 350° C). The narrowness 

 of the lines is well exhibited in the reproduction. The Figures 3 

 and 4 refer to experiments with a calc-spar rhomb placed before 

 the slit of the spectroscope, and a horizontal slit near the source 

 of light. The field of view is divided into three parts : one with the 

 horizontal, one with the vertical vibrations and the third due to 

 natural light *). 



The photograph reproduced in Fig. 3 was made with a gas- 

 oxygen flame, which in later experiments (with similar results) was 



1) R. VV. Wood and P. Zeeman, These Proceediügs. Febr. 1913. 



2) P. Zeeman, These Proceedings, October 1907. 



^) Gf. P. Zeeman and B. Winawer, These Proceedings. January 1010. 



