June 21, 1883] 



NA TURE 



185 



to saturation, and placed separately with contrary polarity as 

 regards each other, the third being neutral. Upon cooling, 

 these three bars were found to have identical and similar 

 polarity. Thus the molecules of this most rigid material, cast 

 steel, had become free at red heat, and rotated under the earth's 

 magnetic influence, giving exactly the same force on each ; con- 

 sequently the previous magnetisation of two of these bars had 

 neither augmented nor weakened the inherent polarity of their 

 molecules. Soft iron gave under these conditions by far the 

 greatest force, its inherent polarity being greater than that of 

 steel. 



I have made numerous other experimenis bearing upon the 

 question of neutrality, but they all confirm those I have cited, 

 which I consider ; ffml ample evidence of the symmetrical 

 arrangement of neutrality. 



Superposed Magnetism. — Knowing that by tcsi m we can 

 rotate or diminish magnetism, I was anxious to obtain by its 

 means a complete rotation from north polarity to neutrality, and 

 from neutrality to south polarity, or to completely reverse mag- 

 netic polarity hy a slight right or left torsion. 



I have succeeded in doing this and in obtaining strong reversal 

 ot polarities by superposing one polarity given whilst the rod is 

 undera right elastic torsion, with another of the opposite polarity 

 given under a left elastic torsion, the neutral point then being 

 reached 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, mag- 

 netised to saturation : the second magnetisation in the contrary 

 sense and torsion should be feebler, -o 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 neu- 

 trality as shown at B, V\sr. 1. 



The apparatus needed is simply a good compound horseshoe 

 permanent magne f , 15 centimetres long, having six or more 

 plates, giving it a total thickness of at least 3 centimetres. We 

 need a sufficiency powerful magnet, as ] find that I obiain a 

 more equal distribution of magnetisoi upon a rod or strip of iron 

 by drawing it lengthwise over a single pole in a direction from 



that pole, as shown in Fig. 2; we can then obtain saturation by 

 repeated drawings, keeping the same molecular symmetry in each 

 experiment. 



In order to apply a slight elastic torsion when magnetising 

 rods or wires, I have found it convenient to attach two brass 

 damn keys to the extremities of the rods, or simply turn the 

 ends at right angles, as shown in the following diagram, by which 

 mean we can apply an ela-tic twist or torsion whilst drawing 

 the pid over the pole of the permanent magnet. We can thus 

 superpose several and opposite symmetrical structures, producing 

 a polar north or south as desired, greatly in excess of that p ssible 

 under a single or even double magnetisation, and by carefully 

 adjusting the proportion of opposing magnetisms so that both 

 polarities have the same external force, the rod will be at perfect 

 external neutrality when free from torsion. 



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

 distance from a maenetic directive needle, we find it perfectly 

 neutral when free of torsion, but the slightest torsion riyht or 

 left at once produces violent repulsion or attraction, according to 

 the direction of the torsion given to the n d, the iron rod or strips 

 of hoop-iron which I use for this experiment being ahle, when 

 at the distance of 5 centimetres from the needle, to turn it 

 instantly 90° on either side of its zero. 



The external neutrality that we can now 1 roduce 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 remarkable degree, a condition quite different to that of 

 ordinary magnetisation, for the same rod, when magnetised to 



satura' ion 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 super- 

 posed magnetism, it is but slightly reduced by variations or 

 numerous torsions, and I have found it impossible to render this 

 rod again free from its double polar effects, except by strongly 

 remagnetising it to saturation with a single polarity. The super- 

 posed mag.iet.sm then becomes a single directive force, and we 

 can then by a few vibrations or torsions reduce the rod to its 

 ordinary condition. 



The effects of superposed magnetism and its double polarity I 

 have produced in a variety of ways, such as by the electro- 

 magnetic influence of ceils, or in very soft iron simply by the 

 directive influence of the earth's magnetism, reversing the rod 

 ami torsion, when held in the magnetic meridian, these rods 

 when placed magnetic west showing distinctly the double polar 

 effects. 



It is remarkable, also, that we are enabled to superpose and 

 obtain the maximum effects on thin strips of iron from a quarter 

 to half a millimetre in thickness, whilst in thicker rods we have 

 far less effect, being masked by the comparatively neutral state 

 of the interior, the exterior molecules then reacting upon those 

 of the in'erior, allowing them to complete in the interior their 

 circle of attractions. 



I was anxious to obtain wires which would preserve this struc- 

 ture against the destructive influence of torsion and vibrations, 

 so that I could constantly employ the same w ires without the 

 comparatively long and tedious process of preparation. Soft 

 iron soon lo es the structure or becomes enfeebled under the con- 

 stant to nnd fro torsions requisite where we desire a constant 

 change of polarity, as described later in the magnetic bells, 

 Hard steel preserves its structure, but its molecular rigidity is so 

 great that we obtain but mere tiaces of any change of | olarity 

 hy torsion. I have found, however, that fine cat drill steel, 

 uiitempered, of the kind employed by watchmakers, is most 

 suitable : these arc generally sold in straight lengths of 30 centi- 

 metre . Wires 1 millimetre in diameter should be used, land 

 when it is desired to increase the force several of these wires, 

 say nine or ten, should be formed into a single rod or bunch. 



The wire as sold is too rigid to give its maximum of molecular 

 rotation elfect. We must therefore give it two entire turns or 

 tvwsts to the right, and strongly magnetise it on the north pole 

 of the magnet whilst under torsion. We must again repeat this 

 Oj eration in the contrary direction, after restoring the wire to its 

 previous position, giving now two entire turns to the left and 

 magnetising it on the south pole. On restoring the wire to its 

 original place it will be extremely flexible, and we may now 

 superpose several contrary polarities under contrary torsions, as 

 already described. 



The power of these wires, if properly prepared, is most re- 

 markable, being able to reverse their polarity under torsion, as 

 if they w ere completely saturated ; and they preserve this power 

 indefinitely if not touched by a magnet. It would be extremely 

 difficult to explain the action of the rotative effects obtained in these 

 wires under any other theory than that which I have advanced ; 

 and the absolute external neutrality that we obtain in them when 

 the polarities are changing, we know from their structure to be 

 perfectly symmetrical. 



I was anxious to show, upon the reading of this paper, some 

 mechanical movement produced by molecular rotation, conse- 

 quently I have arranged two bells that are struck alternately by a 

 polarised armature put 111 motion by the double polarised rod I 

 have already described, but whose position, at 3 centimetres 

 distant from the axis of the armature, remains invariably the 

 same. The magnetic armature consists of a horizontal light steel 

 bar suspended by its central axle ; the belK are thin w ine glasses, 

 giving a clear musical tone loud enough, by the force with which 

 tbey are struck, to be clearly heard at some distance. The arma- 

 ture does not strike these alternately by a pendulous movement, 

 as we may easily strike only one continuously, the friction and 

 inertia of the armature causing its movements to be perfectly- 

 dead-beat when not driven by some external force, and it is kept 

 in its zero position by a strong directive magnet placed beneath 

 its axle. 



The mechanical power obtained is extremely evident, and is 

 sufficient to put the sluggish armature in rapid motion, striking 

 the bells six ti ues per second, and with a power sufficient to 

 produce tones loud enough to be clearly heard in all parts of the 

 hall of the Society. As this is the. first direct transformation of 

 molecular motion into mechanical movement, I am happy to 

 show it on this occasion. 



