( 863 ) 



The component towards the red in the figures is always at the 

 left of its middle line, being concave to it in the central part; 

 the second manifestly curved line is the component towards the violet 

 belonging to the other order. 



The curvature of the middle lines, the demonstration of which is 

 the object of our present experiment, is undoubtedly visible in the 

 figure for 5791. It is still more easily seen by comparison with a 

 straight bit of paper. 



In the figure for 5770 this kind of curvature is absent. 



The asymmetry of the magnetic resolution of line 5791 is at once 

 evident by the fact that one of the middle lines is approached more 

 nearly by the outer component than the other. 



If we denote by rio and a,, the distances of the components to their 

 middle lines, then what I called on a former occasion^) the amount 

 of the asymmetry is equal to do — (h-. This diiference is also equal 

 to the difference of the distances separating the plainly curved lines 

 from the middle lines to which they do not belong, and to which 

 they are convex. 



The two negatives were taken with the same field intensity of 

 about 34000 Gauss. 



The question now arises whether the difference rii, — a,- is equal 

 to twice the shift of the middle line or not. In the first case the 

 asymmetry is brought about solely by the motion of the middle line 

 towards the less refrangible wavelengths, the outer components 

 having undergone a symmetrical displacement relatively to the un- 

 modified line. The other, more general case one would rather expect 

 without hypothesis or without the results of measurements. 



8. In order to test the question by experiment, I have taken on 

 the same negative as well the figures described in § 7 as the un- 

 modified lines. It appeared however rather soon that, in the case 

 of line 5791, only in the most intense fields the separation of the 

 middle lines, taken with field on and with field off, was sufficient 

 to allow measurements. 



I therefore refrain from communicating these experiments. Only 

 one detail of the vacuum tube, charged with mercury and used in all 

 my experiments with strong fields, may perhaps be mentioned. This 

 vacuum tube of the form indicated by Paschen, has a rather wide 

 capillary. That part however of the capillary which is placed in 

 the magnetic field is drawn out. Only over this short distance the 



1) Zeeman, These Proceedings 30 November 1907- 



