105 



For a .satisfactory explaiialioii of the magnetic rotation the same 

 frequencies will have to be taken into consideration ; it should only 



0.4688 



0.03843 



be borne in mind that there is no occasion to assume magnetic 

 resolution for the ultrared frequencies ascribed to positively charged 

 particles, so that these need not occur in the expressions for tlie 

 magnetic rotation. 



For most substances the magnetic rotation is positive. Theory 

 teaches that it can be caused by the magnetic resolution of an ultra- 

 violet spectral line of a sign as determined by the elementary theory' 

 of the ZKKMAN-elfect. To explain negative rotation a magnetic resolu- 

 tion of an ultraviolet line of the abnormal sign must be assumed. 

 Such a resolution need not necessarily be accompanied with a positive 

 charge, of the vibrating |)articles. Voigt ') demonstrates that in con- 

 sequence of couplings between xibrating electrons complicated reso- 



») W. Voigt. Ann. d. Phys. 45 p. 457. 1914. 



