JEAN BECQUEREL 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. 



PL I. 



J-l^. 3, 



£V. 



i.n.n. 



> X i ^ C. ITl^. 



Proceedings Royal Acad Amsterdam. Vol. X. 



