334 Prof. Nagaoka and Mr. T. Takamine on Anomalous 



r> 



according to Zeeman and Gmelin, divided into a triplet 

 showing remarkable dissymmetry. McLennan * made a 

 special study of the Zeeman effect of the green lines o£ 

 mercury, and found that they were mostly divided into 

 quartets in weak fields. Wendt f tried the effect of strong 

 fields, and found that in place of the satellites there appear 

 four new lines, which are nearly at a constant distance 

 from the principal line. A complete study, following the 

 course of satellites in a continuous manner from weak to 

 strong fields, is still wanting ; so that we are still in the 

 dark as to the manner in which the satellites are gradually 

 lost to view and the new lines make their appearance. 

 Most of the experiments hitherto undertaken are confined 

 to the separation of the principal lines ; as to the behaviour 

 of the satellites, it is briefly stated that they are so com- 

 plicated in magnetic fields that the discrimination of the 

 numerous lines as to their origin is extremely difficult. 

 Tedious as it may at first appear, it would not be impossible 

 to trace the course taken by the lines, if the separation 

 in magnetic fields be simply proportional to the strength 

 of the field, as in most of the spectrum lines hitherto 

 investigated, however complicated the manner of separation 

 may be. Our object in the present investigation is to 

 follow the whole course of the change in the lines from 

 weak to strong fields, and to show that the separation of 

 the lines is not generally subject to the law of linear 

 proportionality to magnetic force, including the singular 

 case in which the change of wave-length is proportional 

 to the square of the magnetic field, as one type of separation. 

 We shall further show how the satellites gradually tend to 

 osculate to the branches of the principal line, when the field 

 is sufficiently increased. 



The position of the satellites relative to the principal line 

 was examined mostly by means of an echelon spectroscope 

 constructed by Hilger, and described in our paper on crossed 

 spectra. The spectrum produced by the echelon grating was 

 not free from ghosts, so that it was sometimes necessary to 

 obtain crossed spectra by means of another interferometer, 

 when the existence of the line was doubtful. We tried the 

 combination of echelon w r ith a Lummer-Gehrcke plate, or 

 with a sliding Fabry-Perot interferometer. Both apparatus 

 can be used for the discrimination of false lines ; but the 

 air-plate was especially advantageous, as the thickness can 

 be varied, and by this means doubtful lines more closely 



* McLennan, Proc. Roy. Soc. A. Ixxxvii. p. 269 (1912). 

 f "Wendt, Ann. d. fhys. xxxvii. p. 535 (1912). 



