the Magnetic Rotation of the Plane of Polarization. 727 



the absorption-band it was found that they did not agree very 

 well, the same values for the rotation occasionally beino- 



Fiu. 1. 



found on opposite sides of the band. On this account it 

 seemed best to take a large number of readings for various 

 wave-lengths, the monochromatic illuminator being adjusted 

 by another observer. The readings obtained in this manner 

 are recorded in curve 2, which, while showing the large 

 error- which are liable to be made at the edges of the absorp- 

 tion-hand, gives unmistakable evidence of anomalous rotatory 

 dispersion. By opening the slit of the monochromatic 

 illuminator, and working with more intense, though less 

 homogeneous, light, it was possible to obtain readings through 

 the region of ahsorption, though a good deal of trouble was 

 experienced with the elliptical polarization in this case. The 

 values found in tin- case are plotted in curve 3. I do not, 

 however, attach much importance to them, as the light was 

 Ear from homogeneous. 



The observations recorded in this note were made merely 

 for the purpose of convincing myself of the reality of the 

 phenomenon of anomalous magnetic rotatory dispersion, and 

 a- the only other important piece of work on the subject, 

 that of Schmauss, has been called into question, they may he 

 worth putting on record. 



