JEAN BECQÜEREL and H. KAMERLINGH ONNES. On the absorptionspectra of the 

 compounds of the rare earths at the temperatures obtainable by liquid hydrogen 

 and their change by the magnetic field. 



PI. III. 

 642.27 643 45 650 56 654.25 658.10 



r==290°abs 



T -^ 85° 



r= 20° 



T= 14° 



Fig. 3. Left and righthanded vibration in 3 a field of 18000 Gauss nearly, Xenotime, group in the 

 red, 2d spectrum (Rowland grating); panchromatic plates of Wratten and Wainwright. 



520.6 522.15 537 



r=20°abs 



r=20°abs 



r=14°abs 



5237 

 Fig. 4. Xenotime^ group in the green, 2d spectrum (Rowland grating) 



1. magnetic circulair birefringency, plate thick 0.80 mM., field 15000 Gauss. 



2. images by rhombohedron before slit, the incident light polarized to give equal intensities to 

 the regions in the transparent part in the middle of the group. Field 15000 Gauss. 



3. images given by rhombohedron before slit, incident light polarized under 45° with the horizon; 

 field 18000 Gauss. 



