Maguetic Sépai'ations of the Tjiues of Iron, Xickel and Zinc in Different Fields. 9 



8. Measurement and Reduction. To measure the magnetic 

 separation of photographed lines, I used a dividing machine No. 

 O030'\made by the Société Genevoise. Taking the tracelet off, 1 

 put a supporter of the photographic plate on the platform. Under 

 this supporter, a plane mirror, inclined 45° to the platform, was 

 fixed and by reflecting the light from an electric lamp, the plate 

 was ilkiminated. The platform, and consequently the photo- 

 graphic plate were moved by the rotation of the handle, and the 

 spectral line under examination was placed under a single straight 

 wire of a fixed microscope whose magnification was 20. But when 

 the line was very intense, it was put between two parallel wires. 

 As the magnification was moderately large, the former method 

 gave better results. The drum of the dividing machine was 

 divided into 0'005 mm. and by the aid of the vernier it could be 

 read to 0*001 mm. 



A device was made so as to move the plate in two directions 

 at right angle to each other. Hence the line w^as measured along 

 its length as many times as possible. In the case of the fourth 

 order spectra, as the line is long, measurement can be made on 

 twenty different parts. As this work is very im.portant for finding 

 accurate values the measurements were made b,y inj^self. The 

 result obtained b}' the measurements of one and the same line on 

 different days agreed well with each other. 



III. The Character of the Separation. 



After the publication of Voigt' s"^ asymmetrj^ theory with 

 regard to the magnetic separation, Zeeman^'-* remarked that the 

 asymmetrical intensity of the outer components of a triplet was 

 also due to secondary circumstances, L e. to the reflecting grating 

 and the focussing quartz lens. As, in my case, these two secon- 

 dary circumstances are related to each other I could make out the 

 character distinctly, but it may be of interest to report that on one 



1) Société Genevoise, Price List (1912), Fascicle 1, General Instruments of Measurements, 

 p. 13. 



2) W. Voigt, Ann. d. Phys. (4) 1 (1900), 376. 



3) Zeeman, Versl. Amsterd. Acad., 26 oct. (1907). 



