Magnetic Separations of Inm Lines iu Different Fields. 9 



of the gelatine film of the photographic plate and other sources, 

 photos were taken repeatedly, increasing and decreasing the 

 magnetic field. The photographic plates mostly used were the 

 panchromatic and process plates hy Wratten cfe Wainwriglit. 

 Wratten douhle instantaneous and Ilford procès plates were used 

 occasionally for the stronger and the weaker fields respectively. 



Result. 



In the earlier course of the experiment it was my chief object 

 to study the behavior of the nine strong lines in the violet region 

 //I 4415-13, 4404-75, 4383-55, 4325-78, 4307-92, 427175, 407r75, 

 4063*6], 4045"82'^ over a wide range of magnetic fields. Three of 

 these lines are arranged in a particular spacing, thus. 1 1 |, the 

 distance between the second and the third lines being twice as 

 large as that between the first and the second. Another aim of 

 the investigation was to observe the se]:)arations of the principal 

 lines in the green region, as former results in this region showed 

 some discrepancies, which may have been due partly to experi- 

 mental errors and partly to the difference of the magnetic fields. 

 Tn the course of the experiment it seemed to me important to 

 study tlie separations of weak lines, for a weaker line may l»e 

 afïected more than, a stronger b}^ mutual action, though we do not 

 know the mechanism of radiation in the atom. Thus the resolu- 

 tions of the weak lines, so far as observed with the present instru- 

 ment, are also here given. Many weak lines lost their intensity 

 with the increase of the magnetic field and became very diffuse, 

 some showing complicated resolutions. Especially in the green 

 region the increase of the intensity of the back ground disturbed 

 the echelon spectra so much that they appeared to melt into it, — 

 this phenomenon is somewhat due to the character of these lines, 

 whose components are diffuse or complex and one falling close l)y 



1) The wave lengths of these lines and the others criven in the present report were first 

 identified in the map of the iron spectrum l:>y Buisson and Fabry in " Recueil de Constantes 

 Physiques," and then the exact numbers were taken from the international in Kayser's 

 „Handbuch der Spectroscopic." 



