180 



Prof. D. E. Hughes. 



[May 10, 



M. De La Rive sums rip a series of interesting experiments in these 

 remarkable words : " The whole of the magneto-molecular phenomena 

 that we have been studying lead]us to believe that the magnetisation of 

 a body is due to a particular arrangement of its molecules, originally 

 endowed with magnetic virtue, but which in the natural state are so 

 arranged that the magnetism of the body that they constitute is not 

 apparent. Magnetism would therefore consist in disturbing this state 

 of equilibrium, or in giving to the particles an arrangement that 

 makes manifest the property with which they are endowed, and not in 

 developing it in them. The coercitive force would be the resistance 

 of the molecules to change their relative positions. 



" There remains an important question to be resolved : 



"Are mechanical or other actions, disturbers as they are of the 

 electrical state, able of themselves to give rise to magnetism ?" 



Du Moncel, in his remarkable work on Magnetism, 1857, sustained 

 and developed the views of De La Rive, and later, "Wiedemann in 

 * l Poggendorff's Annalen," 1857 — 1859, as well as in his remarkable 

 " Lehre von Galvanismus," 1861, sustained a similar theory. 

 "Wiedemann has lately given a resume of his researches in the 

 " Lumiere Electrique," Paris, January 28, 1882, where he says — 



"Nous admettons que les metaux magnetiques sont composes de 

 molecules qui ont une polarite magnetique ; nous ne voulons rien 

 preciser quant a la cause meme de cette polarite, qu'elle provienne 

 de la separation des fluids magnetiques, des vibrations d'un milieu 

 entourant les molecules ou mieux encore de l'existance de courants 

 elementaires. 



" "On corps ainsi constitue n'aura pas, en general, de magnetisme 

 libre, parceque les axes magnetiques des molecules seront diriges dans 

 tous les sens et maintenus dans leurs positions respectives par les 

 forces moleculaires. Mais une force magnetique exterieure, telle qu'une 

 helice ou passe un courant, leur donnera une direction generale. 



"En ponrsuivant cette hypothese, M.Weber a reussi a expliquer 

 theoriquement l'accroisement de la magnetisme d'une barre soumise 

 a, 1'influence d'une helice aimantee jusqu'a un maximum. 



" Nous supposons, en outre, que les molecules dans leur mouvement 

 eprouvent une certain resistance qui les empeche de suivre complete- 

 ment 1'influence des forces qui agissent sur elles." 



In my preliminary note I gave the formulated results of a length- 

 ened series of researches upon magnetism by the aid of the induction 

 balance. As these agree in all important points with the theory of 

 De la Rive, 1853, I do not wish it to be considered as a new theory 

 or conception of molecular rotation, but as a theory based entirely 

 upon researches into all the conditions of magnetism, and one which 

 clearly defines the conditions of polarity and neutrality. 



Gilbert, 1600, remarked the influence of torsion, stress, and vibra- 



