(116 ) 



would lie in the very nature of paramagnetism. In that case there would 

 hold for eveiy substance, as was shown in Comm.N". 1J6 to be the 

 case for oxygen, a more general law than Curie's, which only within 

 a definite temperature region would not differ appreciably from Curte's. 

 After we had been engaged upon an investigation in this direction 

 for a considerable time, its importance increased considerably from 

 two different points of view. In the first place came the discovery 

 by Weiss ^) of the magneton as forming a part of all magnetic 

 atoms. Should the deduction advanced by Weiss that the molecular 

 magnetisation of different substances can be expressed as whole 

 multi[)les of the magneton hold for all temperatures, this would, 

 because it supposes that the constant of Clrie is accessible, entail 

 the validity of a law which gives the means to determine this constant, 

 fui'ther allowance having to be made only for sudden changes in the 

 number of magnetons or in the numl)er of degrees of freedom. Certain 

 of our measurements appear to be incompatil)le with exclusively dis- 

 continuons changes, for they even seem to indicate that gradual changes 

 take place. Should this be the case, then it is possible that deviations of 

 the values of the magnetisation from those values which Weiss's theory 

 combined with Curie's law would lead us to expect could be eliminated 

 by means of corrections which our knowledge of these gradual changes 

 would enable us to apply. And if it should ai)pear from further 

 investigation that all deviations could be explained by discontinuous 

 changes, then the knowledge of the law according to which these 

 discontinuities occur is, by the discovery of the magneton, made a 

 matter of the highest imi)Ortance. However the case may be, we 

 shall, in sjjeaking of the deviations from Curie's law mean both 

 continuous and discontinuous changes. 



In the second place the rather indefinite notion of the "freezing 

 of the electrons in the atoms" has taken a more definite shape since 

 it was found (Comm. N". 119, Febr. 1911) that the electrical resis- 

 tance of pure metals disappears in liquid helium and that this can 

 be ascribed to the coming to rest of vibrators of definite frequencies 

 which are ju radiation equilibrium according to Planck's formula. 

 The freezing of the electrons which we mentioned in connection with 

 the magnetisation of oxygen may also be looked for in the coming 

 to rest of vibi-alors. Perhaps then it may also be that, in general, 

 deviations from Curie's law may be found to be connected with 

 the dissipation of the energy of the vibrators ') or of the circular 



') P. WkissTg.R. CL'I p 134, £22, 309, 19il, also: Aidi. de Geneve, May 191 1. 



~) From a friendly teller lliat reached us just on going to press from Professor 

 \Vei!~s, whose coming to Leiden gave the initial impetus to our magnetic resear- 

 ches, we learn that this idea has also occurred to him. 



