SCIENCE. 



[Vol. XVIII. No. 440 



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THE FARADAY CENTENARY. 



On Wednesday, June 17, at the Royal Institution, London, Lord 

 Rayleigh delivered a lecture in conneclion with the one hundredth 

 anniversary of Faraday's birth. The following abstract of the 

 lecture is from Nature of June 2C. 



Lord Rayleigh said that the man whose name and work they 

 ■were celebrating was identified in a remarkable degree with the 

 history of that institution. If they could not take credit for his 

 birth, in other respects they could hardly claim too much. During 

 a connection of fifty-four years, Fai'aday found there his opportu- 

 nity, and for a large part of the time his home. The simple story 

 of his life must be known to most who heard him. Fired by con- 

 tact with the genius of Davy, he volunteered his services in the 

 laboratory of the institution. Davy, struck with the enthusiasm 

 of the youth, gave him the desired opportunity, and, as had been 

 said, secured in Faraday not the least of his discoveries. The 

 early promise was indeed amply fulfilled, and for a long period of 

 years, by his discoveries in chemistry and electricity, Faraday 

 maintained the renown of the Royal Institution and the honor of 

 England in the eye of the civilized world. He should not at- 

 tempt in the time at his disposal to trace in any detail the steps of 

 that wonderful career. The task had already been performed by 

 able hands. In their own " Proceedings " they had a vivid sketch 

 from the pen of one whose absence that day was a matter of lively 

 regret. Dr. Tyndall was a personal friend, had seen Faraday at 

 work, had enjoyed opportunities of watching the action of his 

 muid in face of a new idea. All that he could aim at was to re- 

 call, in a fragmentary maimer, some of Fai-aday's great achieve- 

 ments, and if possible to estimate the position they held in con- 

 temporary science. 



Whether they had regard to fundamental scientific import, or 

 to practical results, the first place must undoubtedly be assigned 

 to the great discovery of the induction of electrical currents. He 

 proposed first to show the experiment in something like its original 

 form, and then to pass on to some variations, with illustrations from 

 the behavior of a model, whose mechanical properties were analo- 

 gous. He was afraid that these elementary experiments would 

 tax the patience of many who heard him, but it was one of the 

 difiiculties of his task that Faraday's discoveries were so funda- 

 mental as to have become familiar to all serious students of phys- 

 ics. 



The first experiment required them to establish in one coU of 

 copper wire an electric current by completing the communication 

 with a suitable battery; that was called the primary circuit, and 

 Faraday's discovery was, that, at the moment of the starting or 

 stopping of the primary current, then, in a neighboring circuit, 

 in the ordinary sense of the words, completely detached, there 

 was a tendency to induce a current. He had said that those two 

 circuits were perfectly distinct, and they were distinct in the 

 sense that there was no conducting communication between them, 

 but, of course, the importance of the experiment resided in this, 

 — that it proved that in some sense the circuits were not distinct; 

 that an electric current circulating in one does produce an effect 

 in the other, which is propagated across a perfectly blank space 

 occupied by air, and which might equally well have been occupied 

 by vacuum. It might appear that that was a very simple and 

 easy experiment, and of course it was so in a modern laboratory, 

 but it was otherwise at the time when Faraday first made it. 

 With all his skill. Faraday did not light upon truth without delay 

 and difBculty. One of Faraday's biographers thus wrote: "In 

 December, 1824, he had attempted to obtain an electric current by 

 means of a magnet, and on three occasions he had made elaborate 

 and unsuccessful attempts to produce a current in one wire by 

 means of a current in another wire, or by a magnet. He still 

 persevered, and on August 29, 1831, — that is to say, nearly seven 

 years after his first attempts, — :he obtained the first evidence 

 that an electric current induced another in a diffei'ent circuit. 

 On Sept. 23 he writes to a friend, ' I am busy just now again with 

 electro-magnetism, and think I have got hold of a good thing, but 

 cannot say; it may be a weed instead of a fish that, after all my 

 labor, I at last haul up.' " We now know that it was a very big 

 fish indeed. 



About the time that the experiments of which he had been 

 speaking were made, Faraday evidently felt uneasiness as to the 

 soundness of the views about electricity held by his contempora- 

 ries, and to some extent shared by himself, and he made elaborate 

 experiments to remove all doubt fi-om his mind. He re-proved 

 the complete identity of the electricity of lightning and of the 

 electricity of the voltaic cell. He was evidently in terror of being 

 misled by words which might convey a meaning beyond that 

 which facts justified. Much use was made of the term " poles" 

 of the galvanic battery. Faraday was afraid of the meaning 

 which might be attached to the word " pole," and he introduced 

 a word since generally substituted, "electrode," which meant 

 nothing more than the way or path by which the electricity was 

 led in. " Electric fluid " was a term which Faraday considered 

 dangerous, as meaning more than they really knew about the na- 

 tui-e of electricity, and, as was remarked by Maxwell, Faraday 

 succeeded in banishing the term " electric fluid " to the region of 

 newspaper paragraphs. 



Diamagnetism was a subject upon which Faraday worked, but 

 it would take too long to go into that subject, though a word or 

 two must be said. Faraday found that whereas a ball of iron or 

 nickel or cobalt, when placed near a magnet or combination of 

 magnets, would be attracted to the place where the magnetic force 

 was the greatest, the contrary occurred if for the iron was sub- 

 stituted a corresponding mass of bismuth or of many other sub- 

 stances. The experiments in diamagnetism were of a microscopic 

 character, but he would like to illustrate one position of Faraday's, 

 developed years afterwards by Sir William Thomson, and dem- 

 onsti'ated by him in many beautiful experiments, only one of 

 which he now proposed to bring before them. Supposing they 

 had two magnetic poles, a north pole and a south pole, with an 

 iron ball between them, free to move along a horizontal line per- 

 pendicular to that joining the poles, then, according to the rule he 

 had stated, the iron ball would seek an intermediate position, the 

 place at which the magnetic force was the greatest. Conse- 

 quently, if the ii'on ball be given such a position, they would find 

 it tended with considerable force to a central position of equili- 

 brium; but if, instead of using opposite poles, they used, e.g., two 

 north poles, they would find that the iron ball did not tend to the 

 central position, because that was not the position in which the 

 magnetic force was the greatest. At that position there was no 

 magnetic force, for the one pole completely neutralized the action 



