m 



Art. 8.— Y. Takahashi 



and the deviations are too small to speak of its existence; in fact, 

 we can connect tliem l)y a straight line which does not pass 

 through the origin. 



(Jf the separations which are not proportional to the magnetic 

 field, some may he caused hy true coupling l)etween radiating or 

 non-radiating electrons, and others b^^ experimental errors. 

 Among the conditions giving rise to the appearance of false 

 coupling, we may count the followii^ : — 



1. p]rrors in the determination of the magnetic field. 



2. Apparent displacement of the mean position of a l)road 

 line in the double order position. 



3. Errors in measuring the broad line. 



4. Disturbance by other coincident or neighbouring lines 

 known or unknown. 



5. Complicated separation whose components are not 

 thoroughly resolved. 



^6. Irregular contraction of the photographic film. 



Those lines photographed on one plate with the same 

 exposure as the standard line ai"e free from the first error, as the 

 standard line was measured most accurately'. For those which 

 were not photograj^hed with the same exposure as the standard 

 line, we can determine the field ])y measuring the photos of the 

 standard line taken before and after the exposure for those in 

 question without breaking the current through the electromagnet 

 and carefully observing the constancy of the current. The 

 separation of the standard line measured on the former agi'eed well 

 Avith that on the latter in ahnost all cases, so tliat we may rely on 

 the determination of the relative field. 



The second is important for broad lines. This can be 

 eliminated by taking the photos in different positions of the echelon 

 spectra, bringing the undisturbed line in single order for some 

 exposures and in double order for others. 



The third is unavoidable, but the use of different types of 

 cross wire somewhat improved the result. The cross wire of the 

 micrometer used by the writer was constructed as showu in Fig. 

 55. a was mostly used for sharp lines to bisect the lino in the 



