( 580 ) 



§ 2. In a former attempt to classify all elements accorfling to 

 their magnetic properties and those of their compounds, the following 

 remarks were made : 



"Les elements nouvellement reconnns: helium, argon ^), neon, 

 "krypton, xenon, n'ont j)as encore été determines ; il n'est guère 

 "probable qu'ils soient autres que diamagnétiques. On pent classer 

 "63 autres elements, dont 37 diamagnétiques, 22 paramagnétiqnes, 

 "4 ferromagnétiques a la temj)érature ambiante ; tandis qu'en 7 cas 

 "(Be, Mg, Sc, Nb, La, Ta, Th) la classification nous parait encore 

 "plus on moins douteuse. Dans le système naturel a masses atomi- 

 "ques croissantes, on pent distinguer 7 séries d'éléments paramag- 

 "nétiques consécutifs, qui les comprennent tons, le signe de Télément 

 ''ouvrant chaque série étant seul encore incertain ; les séries d'ordre 

 "pair sont moius prononcées au })oint de vue paramagnétique que 

 "celles a numero impair" ^). 



These last-mentioned uneven series are: 



1) O. 



■ 3) Sc (?;, 7V, r. Cv, Mn, Fe, Co, Ni, Cu ') 



5) La (?), Ce, Fr, Nd, Sa, Eu, Gd, Th, Dp, Er, Yb. 



7) Ra{^), Th (?), U. 



Now the anorganic compounds ^) which chiefly absorb light select- 

 ively, evidently belong to these paramagnetic series; this connection 

 is so remarkable that it can hardly be an accidental one. 



From this profuse supply of material only a few samples could 

 be chosen ; we have thought that we ought to extend the investigation 

 in the first place to matter which was comparatively easily to be 

 had in larger pieces; among others to some coloured gems, w^hich 

 are to be considered as dilute solid solutions, to certain micro- 

 crystalline salts, but also to amorphous solidified molten matter and 

 to glassy solid solutions in an amorphous substratum, e. g. borax 

 or glass. The crystalline structure gives rise to complications which 

 render the phenomena very intricate, though they are most interest- 

 ing in themselves. All this yields a rather extensive material of 

 observation, possibly of inqiortance in connection with molecular 

 theories on solid and liquid substances. 



With the available cryomagnetic arrangement we could expose 

 matter in liquid air to a strong .magnetic field ; in many cases we 



1) Recently confirmed by P. Tanzler, Ann. d. Physik. (4) 24 p. 931, 1907. 



2) Rapp. Gongi-. d. Phys. 2 p. 487, Paris 1900. 



■') 0. LiEBKNECHT & A. P. WiLLs, Ann. d. Physik (4) 1 p. 186, 1900. 

 *) See H. Kayseu, Handb. d. Spectroscopie 3 ; Leipzig 1905. 



