MICHAEL FARADAY — HIS LIFE AND WORKS. 241 



covery to wliicli I have just alluclecl is that as the magnet acts by attraction 

 upon magnetic bodies, it acts also by repulsion upon all other bodies in nature. 

 From this it results that whilst a rod of iron, or of some other magnetic sul)- 

 stance, suspended between the poles of an electro-magnet, places itself axiall//, 

 (that is to sa}^, parallel to the line which joins the poles,) a prism of heavy 

 glass (the same, for example, which served for the experiments on light) places 

 itself equatorially, (that is to sa}', transversely to this line.) A rod of bismuth 

 is in the same case ; and this metal and heavy glass are the substances on 

 which this repulsive action of the magnet is most distinctly exerted ; but all 

 l»odies in nature which are not magnetic (and these arc by far the most numer- 

 ous) present the same property, although in various degrees. In this way 

 Faraday comes to class all bodies under two heads : those which are magnetic 

 or paramagnetic, as he calls them, such as iron, nickel, &c. ; and those which 

 are diamagnetiCj such as bismuth, antimony, heavy glass, &c. The character 

 of the former is to be attracted by the magnet, that of the latter to be repelled 

 by it. It is true that this repulsion, to become sensible, requires an enormous 

 magnetic power even in the case of bodies of which the diamagnetism is most 

 strongly marked, whilst a very weak magnet is sufficient to betray its action 

 upon the magnetic bodies^ such as iron, steel, nickel, (Sec. 



It therefore required very powerful means, such as Faraday employed, for the 

 discovery of diamagnetism. Nevertheless a distinguished amateur in science, 

 M. Lebaillif of Paris, had shown, as early as 18:28, that a fragment of bismuth 

 or antimony very evidently repels a delicately suspended magnetized needle 

 when brought as near as possible to one of the poles of the needle, but without 

 touching it. Mr. Faraday was ignorant of this circumstance when he published 

 his first work on diamagnetism. I immediately informed him of it, at the same 

 time indicating the journal in which I had published M. Lebaillif 's experiment, 

 Avhich I had witnessed at the time. He accepted my reclamation in the most 

 amicable manner, and at once, with his usual good laith, recognized the priority 

 of M. Lebaillif with regard to bismuth and antimony. 



In the numerous researches which Faraday devoted (from 1845 to 1855) to 

 diamagnetism and at the same time to magnetism, there are some important 

 points which I must indicate. Ho discovered the remarkable influence exerted 

 iipon this kind of properties by the molecular constitution of bodies, and espec- 

 ially by crj'Stallization, He showed, for example, that a crystallized lamina 

 of bismuth or antimony can place itself axially between the poles of an electro- 

 magnet like a magnetic body, as well as equatorially, and that the position 

 which it takes depends on the manner in which it is suspended relatively to the 

 direction of its cleavage. He endeavored to investigate the force which comes 

 into play in facts of this order, which he names magnefocn/s(alUne force ; whilst 

 Pliicker, on his part, widened its field by his beautiful and numerous researches 

 on the manners in which crystals place themselves between the poles of an 

 electro-magnet ; and Tyndall, the worth}'^ successor of Faraday at the Royal 

 Institution, by his ingenious experiments anah'zed the jjlienomenon in its gener- 

 ality and succeeded in connecting it, in a perfectly satisfactory manner, with 

 the laws which govern magnetism and diamagnetism. Subsequently Tyndall 

 succeeded also in demonstrating, by a decisive experiment, that diamagnetism, 

 like magnetism, is due to a polarity caused by the influence of the magnet in 

 the diamagnetic body, but with this difference, that, instead of opposite poles, 

 homonymous poles are developed by the poles of the magnet. Thus fell to the 

 ground all the other more or less rash attempts at explanation which had been 

 given of diamagnetism. 



Another point which deserves attention is the investigation which Faraday 



made of the magnetism and diamagnetism of gases. He arrived at this curious 



result, (observed likewise by Edmond Becquerel at the same time,) that of all 



gases oxygen alone is magnetic, and this in a very marked degree, while all the 



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