1884.] on the Theory of Magnetism. 3 



2. That each molecule can be rotated in either direction upon its 

 axis by torsion, stress, or by physical forces such as magnetism and 

 electricity. 



3. That the inherent polarity or magnetism of each molecule is a 

 constant quantity like gravity ; that it can neither be augmented nor 

 destroyed. 



4. That when we have external neutrality, or no apparent mag- 

 netism, the molecules arrange themselves so as to satisfy their mutual 

 attraction by the shortest path, and thus form a complete closed 

 circuit of attraction. 



5. That when magnetism becomes evident, the molecules and 

 their polarities have all rotated symmetrically, producing a north 

 pole if rotated in a given direction, or a south pole if rotated in the 

 opposite direction. Also, that in evident magnetism we have still 

 a symmetrical arrangement, but one whose circles of attraction are 

 not completed except through an external armature joining both 

 poles. 



6. That we have permanent magnetism when the molecular 

 rigidity, as in tempered steel, retains them in a given direction, and 

 transient magnetism whenever the molecules rotate in comparative 

 freedom, as in soft iron. 



Experimental Evidences. 



In the above theory the coercive force of Poisson is replaced by 

 molecular rigidity and freedom ; and as the effect of mechanical 

 vibrations, torsion, and stress upon the apparent destruction and 

 facilitation of magnetism is well known, I will, before demonstrating 

 the more serious parts of the theory, make a few experiments to prove 

 that molecular rigidity fulfils all the requirements of an assumed 

 coercive force. 



I wdll now show you that if I magnetise a soft iron rod, the 

 slightest mechanical vibration reduces it to zero ; whilst in tempered 

 steel or hard iron, the molecules are comparatively rigid, and are but 

 slightly affected. The numerous experimental evidences which I 

 shall show prove that whilst the molecules are not completely rigid 

 in steel, they are comparatively rigid when compared with the 

 extraordinary molecular freedom shown in soft iron. {Experiments 

 shown.) 



If I now take a bottle of iron filings, I am enabled to show how 

 completely rigid they appear if not shaken ; but the slightest motion 

 allows these filings to rotate and short circuit themselves, thus pro- 

 ducing apparent neutrality. Now I will restore the lost magnetism 

 by letting the filings slowly fall on each other under the influence 

 of the earth's magnetic force ; and here we have an evident proof of 

 rotation producing the result, as we can ourselves perceive the 

 arrangement of the filings. {Experiment shoivn.') 



If I take this extremely soft bar of iron, you notice that the 



B 2 



