CONSTITUTION AND TEMPERATURE ON MAGNETIC SUSCEPTIBILITY. 103 



Prof. J. W. NICHOLSON during the discussion on " The Structure of the Atom " (issued 

 with ' Roy. Soc. Proc.' for July 20) are interesting : 



"I think that Prof. RUTHERFORD has made it clear that the nuclear atom is, as a 

 matter of fact, the only basis upon which profitable discussion of the constitution of 

 the atom can really be carried on. The main rival theory, as Prof. HICKS has just 

 indicated, is the magneton theory. It seems that just recently in the course of a 

 discussion it has been shown that the magneton theory and the nuclear theory do 

 probably amount to exactly the same thing." 



Future work will test this. But in the meantime it is clear that the magnetic 

 forces cannot be neglected.] 



Note added February 1, 1915. 



While this work has been passing through the press, some further extensions have 

 been made. In particular, there is one which I should like to refer to here because 

 it bears directly upon the foregoing work, 



It can be shown that the magnitude of the change of volume observed on 

 crystallization may be interpreted as the magneto-stnctioii effect of the local 

 molecular field. We have seen that the natural double refraction of a crystalline 

 medium may be represented as due to the complete orientation of the molecules by 

 the local molecular field. As the magneto-striction effect produced in a liquid and 

 the induced magnetic double refraction are each proportional to the square of the 

 applied field intensity, these results mutually support one another. 



The further extension of the work is concerned with the validity of the quantum 

 theory as applied to magnetic phenomena. A discussion of the nature of the magnetic 

 properties of HEUSLER'S alloys, from the points of view developed in the present 

 work, will also be given. I hope to publish an account of these extensions in a future 

 communication. 



