( 9'^ ) 



molecule in tbc Held, the simple spectral liuc must be separated into 

 a j;-fold liue, in sucb a way, tbat the position of tbe different com- 

 ponents is symmetrical to the right and left of tbe original line. 

 From this it follows, tbat if p is odd, one component remains at 

 the place of the original line. 



It seems bowever very difficult to conceive a system, having 

 really, as is necessary for quadruplets, four equivalent degrees of 

 freedom, especially if in addition to this, it is required tbat the values 

 of cc and j'i must be independent of tbe direction of the magnetic 

 force, relatively to tbe molecule. I have not been able to find out 

 a system, really fulfilling these conditions. It is true, it might be 

 argued tbat tbe very existence of a quadruplet proves tbe equality 

 of four frequencies, when there is no magnetic field, and hence tbat 

 the above theory of the quadruplet must be true, even though the 

 mechanism has not yet been found out. However I have some scruples 

 to be satisfied with this view of the case, for I think, it is not yet 

 quite certain, tbat tbe vibrations which produce light are really 

 to be described by equations of tbe form (1). 



Physics. — On an Asymmetry in the Change of the spectral Lines 

 of Iron, radiating in a Magnetic Field. By Dr. P. Zeeman. 



1. It is known that in the elementary treatment of the influence 

 of magnetic forces on spectral lines according to Lobentz's theory 

 it is sufficient, if only one spectral line is considered, to suppose 

 tbat in every luminous atom is contained one single moveable ion 

 moving under an attraction proportional to the distance from its 

 position of equilibrium. All motions of such an ion can be resolved 

 into linear vibrations parallel to the lines of force and two circular 

 vibrations, righthanded and leftbanded perpendicular to the lines 

 of force. The period of tbe first mentioned vibration remains un- 

 changed, those of the last are modified, one being accelerated and the 

 other retarded. Tbe doublets seen along tbe axis of the field, the 

 triplets seen across it are in this manner simply explained and 

 also tbe observed polarisation- phenomena. Besides we must expect 

 according to tbe theory that the outer components of tbe triplet are 

 of equal intensity and likewise the two circularly polarized com- 

 ponents of the doublet. Eye observations as well as the negatives 

 taken by myself and others have always confirmed till now this 

 most simple symmetrical distribution of intensities. The question arises 

 cannot the external magnetic forces, sufficient to direct the molecular 



