162 



NA TURE 



[June 14, 1883 



■degree of frictional rigidity, then, upon passing one pole of a 

 magnet above them, they would turn symmetrically in one direc- 

 tion, and drawing the same pole of the magnet in the contrary 

 direction would rotate them, and they would then remain sym- 

 metrically in the opposite direction. 



A precisely similar effect takes place in a soft iron rod, placed 

 east and west a few inches above a direction needle. Upon 

 drawing the south pole of a powerful natural magnet at a few 

 centimetres distance above the wire from east to west, the north 

 polarities of the molecules successively turn in the direction of 

 « est, following the attraction of the south pole, as previously 

 seen on the small compass needles. The rod is now magnetised 

 with its north pole west, as indicated by the direction needle 

 below any portion of this rod. Upon passing the same south 

 pole of the natural magnet in a contrary direction, the molecules 

 all rotate, their north poles still turning successively to the south 

 pole of the permanent magnet until its arrival at the end from 

 which the first magnetisation commenced. The rod has now 

 entirely changed its p .larity, and its north pole is east. 



This phenomenon is well known in the ordinary magnetisation 

 of rod , where care is taken to draw the magnet always in a 

 similar direction, or the poles would be reversed at each to and 

 fro drawing. To account for this on Coulomb-Poisson's theory 

 it would be requisite that, first, all the fluids be separated with 

 their north Raids symmetrically in one direction, but on drawing 

 hack the magnet these fluids would have to mix together, the 

 north fluid pas ing through its south fluid to be finally opposite 

 to its previous position, its coercive force doing the double work 

 of allowing both Quids to mix and pass through each other, and 

 finally keep them entirely apart. Ampere's theory would require 

 that from a haphazard arrangement the molecules should become 

 symmetrically arranged upon the fir-t passage of the magnet, 

 then upon its rever-ed direction one-half of the electric elemen- 

 tary currents sh< uld successively revolve in a contrary direction 

 to arrive at neutrality before, finally, the other half followed 

 the direction of the tnst half, and now all these currents would 

 be revolving in the opposite direction to that upon the first 

 magnetisation. We thus see that both these theories, whilst 

 ; altogether upon assumption, are extremely complicated 

 and improbable. 



We might snpp >se, from the theory which I am advocating', 

 that upon the rotation of the molecules there would be some 

 disturbance or mechanical trepidation ; and such is found to be 

 the case, as first observed by Page and afterwards verified by Dr. 

 Joule and De la Rive, in the molecular sounds produced in iron 

 upon its magnetisation. Reis's first telephone was founded upon 

 the-e sounds, and Du Moncel has made numerous researches upon 

 this subject. 



In the last of my experiments cited the sounds are too feeble 

 to be heard, but by the application of the microphone these 

 trepidations at once become audible. 



That molecules of iron and other metals rotate with time, 

 whose peri 'd becomes shortened by mechanical vibrations, is 

 well known in metallurgy, the ultimate result being generally the 

 passage from a fibrous condition, as in iron wires, to a high 

 of crystallisation. For many years I employed a circular vibrating 

 spring as the regulator of speed of my printing telegraph instru- 

 ment, and although this spiring was so regulated by means 1 f a 

 fricli mal break, or " Frein," as not to surpass its limits of 

 elasticity, the e springs were constantly breaking after a few days' 

 use, and as a matter of urgent necessity I made special researches 

 into the cause of this breaking after a few days' constant vibra- 

 tory action. I found at the point of rupture a high state of 

 crystallisation. Fibrous iron would thus become thoroughly 

 crystallised and break in one day ; the number of vibrations for 

 an instrument in constant use during 24 hours being 1,209,600. 

 Thus we could roughly estimate the life of iron in the form of 

 one of these springs at 1,000,000 vibrations. Copper crystal- 

 lised in one hour, and all metals and alloys were infer i. 11 t > steel, 

 except aluminium bronze. The latter springs would stand six 

 weeks' constant use, or some 50,000,000 of vibrations. I finally 

 resolved this problem by spreading the amount of vibrating work 

 over a spiral -pring containing 3 metres of steel rod wound into 

 the same space as previou-ly held by the straight rod of 30 

 centimetres ; by this means the average life of these springs has 

 become five years. Evidently the molecules of these fibrous 

 springs must have ro:ated under the vibrations, in order to 

 produce crystals. The same phenomenon is observed in axles 

 of carriages receiving constant trepidations, large crystals being 

 always found at the point of fracture. Again, if we rapidly 



magnetise and demagnetise an iron rod, we have the production 

 of evident heat, due to the constant motion'of its molecules. 



Maxwell describes an experiment of Beetz, in which an 

 exceedingly small filament of iron was deposited by electrotype, 

 under the influence of a strong magnetic field, in order to arrive 

 at the inherent polarity of comparatively few molecules, and, as 

 its magnetic force was very great, he regards the experiment as 

 conclusive. My own experiments show that we have far less 

 external magnetic force from a solid bar than from a thin tube or 

 flat bar of the same surface exposed to a limited exciting cause. 

 We know that magnetism does not penetrate to a very great 

 depth, and we also know that, if to a thin steel permanent 

 magnet we place another piece unrnagneti-ed, or, better still, a 

 rod of soft iron, its external piolarity is greatly reduced, conse- 

 quently the external evidence of polarity is not a direct measure of 

 the degree of rotation, nor of the total inherent polarity of its 

 mass. We may have a great superficial external rotation super- 

 posed upon rotations of an opposite nature, as will be seen 

 later ; and thus the internal molecules f a magnet often act 

 more or less as an external armature in closing its circle of 

 attractions. 



I have stated my belief that the molecule itself possesses its 

 inherent polarity, which, like gravity, is an endowed quality for 

 w-hich we have no more reason to suspect the cause to be ele- 

 mentary electric currents than that elementary currents should 

 be the cause of gravity, chemical affinity, or cohesion, and its 

 polar power of crystallisation, most of which are affected by an 

 electric current. We have a certain analogy between electric 

 currents and magnetism, but not so great as the analogy between 

 the magnetic polarity of a molecule and its other endowed 

 qualities. 



Magnetism, like chemical affinity, cohesion, and crystallisation, 

 has its critical points. Faraday discovered that at red-yellow 

 heat iron instantly lost its app ' magnetic power, to be 



as instantly restored at red heat, the critical point varying in 

 iron, steel, &c, and being the lowest in nickel. This would be 

 difficult to explain upon Ampere's theory, as we should have to 

 admit the instant des' ruction oi a of the elementary cur- 



rents, to be a_'ain restored at a few degrees less temperature. It 

 would be equally difficult to explain under my view, if it did not 

 belong to a whole class of phenomena due to the posse-sion by 

 the molecules of various endowed qualities, of which chemistry 

 and all our means of research can only teach us their critical 

 points, without attempting to explain why. for instance, iron has 

 a greater affinity for oxygen than gold. We know thai it is so ; 

 we know that the molecules of all matter are endowed with 

 certain qualities bavin; certain critical points, and I can see no 

 reason for separating their magnetic inherent polarity from their 

 numerous other qualities. 



( To be continued. ) 



METERS FOR POWER AND ELECTRICITY^ 



^PIIF. subject of this evening's discourse, "Meters for Power 

 •*■ and Electricity," is unfortunately, from a lecturer's point 

 of view, one of extreme difficulty; for it is impossible to fully 

 describe any single instrument of the class without diving into 

 technical and mathematical niceties which ihis audience might 

 well consider more scientific than entertaining. If then in my 

 endeavour to explain these instruments and the purposes which 

 they are intended to fulfil in language as simple and as untechnical 

 as possible, I am not as successful as you have a right to expect, 

 I must ak you to lay some of the blame on my subject and not 

 all on myself. 



I shall at once explain what I mean by the term "meter,' 

 and I shall take the flow of water in a trough as an illustration 

 of my meai ing. If we hang in a trough a weighted board, 

 then when the water Sows past it the board will be pushed back; 

 when the current cf water is strong the board will be pushed 

 back a long way ; when the current is less it will not be pushed 

 so far ; when the water runs the other way the board will be 

 pushed the other way. So by ob erving the position of the 

 board we can tell how strong the current of water is at any 

 time. Now suppose we »i-h to know, not how strong the cur- 

 rent of water is at this time or at that, but how much water 

 altogether has passed through the trough during any time, as 

 for instance one hour. Then if we have no better instrument 

 than the weighted board, it will be necessary to observe its 



1 Lecture at the Royal Institution, by Mr. C. Vernon Boys, March 2. 



