[ 247 ] 



VIII. The Influence of Molecular Constitution and Temperature on Magnetic 



Susceptibility. 



Part IV. Further Applications of the Molecular Field. 



By Major A. E. OXLEY; R.A.F., M.A., D.Sc., Mackinnon Student of the 



Royal Society. 



Communicated by Prof. J. W. NICHOLSON, F.R.S. 

 Received May 1, Kead June 26, 191<J. 



CONTENTS. 



Page 



(1) Introduction 247 



(2) On the energy and ultimate tensile strength associated with crystalline media or gels . . 250 



(3) A comparison of the elastic constants of diamagnetic, paramagnetic, and ferro-magnetic 



crystalline media 257 



(4) On the change of volume on crystallization interpreted as a magneto-striction effect of the 



molecular field 259 



(5) Further discussion of the nature of the molecular field 267 



(6) On a magnetic theory of chemical combination 277 



(7) On some anomalies of the Faraday effect 282 



(8) Summary of conclusions 286 



(l) INTRODUCTION. 



THE present work is a continuation of that published in ' Phil. Trans., Royal Society,' 

 vol. 214, pp. 109-146, 1914 (Parts I. and IT.) and vol. '215, pp. 79-103, 1915 (Part 

 III.).* It will lead to clearness in the following development of the subject if a brief 

 resume of these papers is given. At the same time, I wish to discuss one or two 

 points in connexion with the views which have been previously advanced and the 

 relation between mechanical and molecular theory. 



In Part I. the experimental evidence brought forward has justified the hypothesis 

 of molecular distortion enunciated at the outset. We have thereby been led to 

 regard the molecular configuration of a material medium as a distorted one, and this 

 applies particularly to a substance which is crystalline. The extent of this distortion 

 is small, but is sufficient to account for the observed change of specific susceptibility 

 which occurs on crystallization. Such change will naturally depend upon the 

 particular crystalline symmetry assumed by the substance. 



The theoretical treatment given in Part II. is an attempt to account for the 

 phenomena observed by extending the electron theory developed by LANGEVIN so 

 * For brevity, reference to these researches is given under Parts I., II., and III. 



VOL. CCXX. A 578. 2 M [Publiihed, April 9, 1920. 



