1884.] on tJie Theory of Magnetism. 5 



where I find the same deflection as before (45°). This happens to be 

 at twice the distance, or 16 inches, so we know, according to the law of 

 inverse squares, that the iron has four times the magnetic power of 

 the atmosphere. But this is only true for this piece of iron : with 

 extremely fine specimens of iron I have been enabled to increase the 

 force of the coil forty times, whilst with manganese steel containing 

 10 per cent, of manganese it was only 30 per cent, superior. We see 

 here that the atmosphere is extremely magnetic. Let us replace 

 the solid bar by iron filings. We now only have twice the force. 

 Replace this by a bottle of sulphate of iron in a liquid state : it is 

 now a mere fraction superior to the atmosphere ; and if we were still 

 further to separate the iron molecules, as in a gaseous state, it is 

 reasonable to suppose that if we could isolate the iron gas from that 

 of ether, that iron gas would be strongly diamagnetic, or have far 

 less magnetic capacity than ether, owing to the great separation of its 

 molecules. These are assumptions, but they are based upon experi- 

 mental evidences, which give it value. 



Let us quit the domain of assumption to enter that of demonstra- 

 tion. Here I have a long bar of neutral iron. If I place this small 

 magnet at one end, we notice that its pole has moved forward three 

 inches, having a consequent point at that place. Let us now vibrate 

 this rod, and you notice the slow but gradual creeping of the con- 

 duction until at the end of two seconds it has reached 14 inches. 

 The molecules have been freed from frictional resistance by the 

 mechanical vibrations, and have at once rotated all along the bar. 

 (Experiment shown.) Let us repeat this experiment by heating the 

 rod to red heat. You notice the gradual creeping or increased con- 

 duction as the heat allows greater molecular freedom. (Experiment 

 shoivn.) Let us now again repeat this experiment by sending a 

 current of electricity through the bar. You notice the instant 

 that I touch the bar with this wire, conveying the current 

 through it, that we have identically the same creeping forwards, no 

 matter what direction of the current. (Experiment shown.) If you 

 simply looked at the effects produced, you could not tell which 

 method I had employed ; either mechanical vibrations, heat vibra- 

 tions, or electrical currents. Consequently, knowing the two first to 

 be modes of motion, it is fair to assume that an electrical current is 

 a mode of motion, the manner of which is at present unknown ; but 

 that there is a molecular disturbance in each case is evident from the 

 experiments shown. 



Neutrality. 



If I take this bar of soft iron, introduce it in the coil, and pass a 

 strong electric current though the coil, you notice that it is intensely 

 magnetic, holding up this large armature of iron and strongly deflect- 

 ing the observing needle. I now interrupt the current, the armature 

 falls, and the needle only shows traces of the previous intense 

 magnetisation. What has become of this polarity? or what has 



