III. The Influence of Molecular Constitution and Temperature on Magnetic 



Susceptibility. 



Part ITI. On the Molecular Field in Diamagnetic Substances. 



By A. E. OXLEY, M.A., M.Sc., Coittts Trotter Student, Trinity College, Cambridge, 



Mackinnon Student of the Royal Society. 



Communicated by Prof. Sir J. J. THOMSON, O.M., F.R.S. 

 Received June 24, Bead June 25, Revised December 2, 1914. 



CONTENTS. 



Page 



(1) Introduction 79 



(2) On the local molecular polarization and the local molecular forces within diamagnetic fluid 



and crystalline media . 80 



(3) The mean and local molecular fields of a diamagnetic crystalline substance 81 



(4) On the magnitude of the local molecular field 84 



(5) On the stresses and energy associated with the molecular field 90 



(6) Additional experiments 96 



(7) A relation between the magnetic double refraction of organic liquids and the change of 



magnetic susceptibility due to crystallization 97 



(8) On the nature of the molecular field 100 



(l) INTRODUCTION. 



IN the present communication an attempt is made to examine to what extent the 

 crystalline state of diamagnetic substances (which form a very large proportion of 

 the whole number of substances known to us) involves mutual actions between the 

 constituent molecules and to obtain a measure of the forces which hold the molecules 

 together in a definite space lattice characteristic of the substance. The work is thus 

 a continuation of that published in 'Roy. Soc. Phil. Trans.,' vol. 214, pp. 109-146, 

 1914, wherein it was shown how from determinations dealing with the change of 

 diamagnetic property on crystallization information could be derived concerning the 

 inner structure of crystalline media and the intensity of the interacting molecular 

 forces. 



In the paper cited (p. 143) it was suggested that the local molecular field within 

 diamagnetic crystalline media may be comparable with the ferro-magnetic molecular 



(525.) [Published February 16, 1915. 



