200 



Prof. D. E. Hughes. 



[May 10, 



My researches upon the molecular structure of neutrality required 

 various kinds of iron and steel; my friend, Mr. W. H. Preece, F.R.S., 

 kindly used his influence with the wire manufacturers supplying the 

 Government telegraphs in procuring for me sixty different samples of 

 iron and steel of a similar gauge, but of different qualities, as the 

 induction balance has since proved, and the results obtained will be 

 given in a future paper upon the " Molecular Structure of Iron and 

 Steel." 



Superposed Magnetism. 



Knowing that we can rotate or diminish magnetism by torsion, I 

 was anxious to obtain a complete rotation from north polarity to 

 neutrality, and from neutrality to south polarity, or to completely 

 reverse magnetic polarity by a slight right or left torsion. 



I have succeeded in doing this and obtaining strong reversal of 

 polarities, by superposing one polarity given whilst the rod is under a 

 right torsion with another of the opposite polarity given under a left 

 torsion, the neutral point then being when the rod is free from torsion. 

 The rod should be very strongly magnetised under its first or right- 

 hand torsion, so that its interior molecules are rotated, or, in other 

 words, magnetised to saturation ; the second magnetisation in the 

 contrary sense and torsion should be feebler, so as only to magnetise 

 the surface, or not more than one-half its depth ; these can be easily 

 adjusted to each other so as to form a complete polar balance of force, 

 producing when the rod is free from torsion the neutrality as shown 

 at B, fig. 6. 



If we now hold one end of this rod at a few centimetres distance 

 from a magnetic directive needle we find it perfectly neutral when 

 free of torsion, but the slightest torsion right or left at once produces 

 violent repulsion or attraction, according to the direction of the torsion 

 given to the rod, the iron rod or strips of hoop-iron which I use for 

 this experiment being able, when at the distance of 5 centims. from 

 the needle, to turn it instantly 90° on either side of its zero. 



The external neutrality that we can now produce at will is absolute, 

 as it crosses the line of two contrary polarities, being similar to the 

 zero, of my electric sonometer, whose zero is obtained by the crossing 

 of two opposing electric forces. 



This rod of iron retains its peculiar powers of reversal in a re- 

 markable degree, which distinguishes it completely from ordinary 

 magnetisation, for the same rod when magnetised to saturation under 

 a single ordinary magnetism loses its evident magnetism by a few 

 elastic torsions, as I have already shown, but when it is magnetised 

 under the double torsion with its superposed magnetism, it is but 

 slightly reduced by vibrations or numerous torsions ; and I have 

 found it impossible to render this rod again free from its double polar 



