6 Professor D. E. Hughes [Feb. 29, 



caused this sudden neutrality ? Coulomb supposes tliat the magnetic 

 fluids have become mixed in each molecule, thus neutralising each 

 other. Ampere supposes that the elementary currents surrounding 

 each molecule have become heterogeneous. De la Rive, Wiedemann, 

 Weber, Maxwell, and all up to the present time have accounted for 

 this disappearance as a case of mixture of polarities or heterogeneous 

 arrangement. 



My researches proved to me that neutrality was a symmetrical 

 arrangement ; I stated this in my paper upon the theory of magnetism 

 to the Royal Society last year. I have since made a long series of 

 researches upon this question, and my paper upon this subject wdll 

 shortly be read at the Royal Society. This paper will demonstrate 

 beyond question — 1. That a bar of iron under the influence of a 

 current or other magnetising force is more strongly polarised on the 

 outside than in the interior ; that its degree of penetration follows the 

 well-defined law of inverse squares, up to the saturation point of 

 each successive layer. 2. The instant that the current ceases, a 

 reaction takes place, the stronger outside reacting upon the weaker 

 inside, completely reversing it, until its reversed polarity exactly 

 balances the external layers. 



We might here suppose that there existed two distinct polarities 

 at the same end of a neutral bar, but this is only partially true, as 

 the rotation of the molecules from the inside to the exterior is a 

 gradual, well-defined curve, perfectly marked, as shown in the 

 diagrams. (Diagrams explained.) We see from these that in a large 

 solid bar the reversed polarity would be in the interior, but in a thin 

 bar under an intense field, the reversed polarity would be on the 

 outside. Thus a bar which had previously strong north polarity 

 under an external influence would, the instant it formed its neu- 

 trality, have a north polarity in the interior covered or rendered 

 neutral by an equal south exterior, the sum of both giving the 

 apparent neutrality that we notice. I must refer all interested 

 upon this question to my paper shortly to be read, but I will make 

 a few experiments to demonstrate this important fact. 



If I take this piece of soft steel and magnetise it strongly, it has a 

 strong remaining magnetism, or only partial neutrality. If I now 

 heat this steel to redness, or put it into a state of mechanical vibra- 

 tion, the remaining magnetism almost entirely disappears, and we 

 have apparent neutrality. This piece of steel being thin (^ millimetre), 

 I know that the outside is reversed to its previous state. I place this 

 piece of steel in a glass vase near the observing needle, and at present 

 there seems no polarity. I now pour dilute nitric acid upon it, filling 

 up the vase. The exterior is now being dissolved, and in a few 

 minutes you will see a strong polarity in the steel, as the exterior 

 reversed polarity is dissolved in the acid. (Experiment sJwivn.) 



Let us observe this by a difierent method. I take two strij)s of 

 hard iron, and magnetise them both in the same direction. 



If I place them together and then separate them, there seems no 



