Magnetic Stiaiatious vî Iren Lines in Different FieLl.s. 



67 



Fig. 55. 



mean position, // was used for In-uad lines 

 bringing the point of intersection of the wire 

 on tlie mean position, and c was used for 

 those which were photographed with the 

 narrow second sht s^ bringing the spot in the 

 middle of the two adjacent wires. 

 c ■■{■ «c Tlie fourth is unavoidal)le, unless we use 



other instruments with different constants, 

 or by crossing them. Plane grating crossed with echelon or 

 other interferometer seems to be most convenient for such an 

 element rich in lines as iron, though the experinent failed in 

 the present work owing to insufHcient intensit}'. While 4957*62, 

 4020'52 and 489 To 1, which jnay be disturbed more or less by 

 neighbouring lines, show separations approximately proportional 

 to the field, 5477-12 (Ni), 526953, 4442':;4 and 4250-79 give 

 separations which are not proportional to the field with some 

 indication of the disturbance caused bv the neigh1)0uring line. 



In order to overcome the fifth difficulty, an instrument of 

 high resolving power with considerably large value of o?.ma.v i^ 

 necessary, for we have to resolve the components in différent 

 positions. If dÀmax is small, many components fall close to the 

 others, and it is difficult to study their l-ehavior with a sufficient 

 number of fields. It is also necessary to apply a strong magnetic 

 field. In the present experiment 4415*13, giving a separation 

 which is not proportional to the magnetic field in weak fields, is 

 resolved into seven components in fields above 35000 gauss. The 

 separation of the n-components of 4447-72, given in Fig. 32, also 

 showa false curvature, the mean position of the two componefits 

 moving from the inner to the outer. The separations of other 

 diffuse components may be subject to the same error, if they are 

 formed of assemblages of several lines, and the measured positions 

 correspond to the means. 



To overcome the last difficulty it is necessary to measure the 

 separation on different plates and increase the number of the 

 observed points. In the present investigation I took great care to 

 avoid these errors. 



