ELECTRO-MAGNETISM. 



CHAPTER I. 

 History of the Science prior to 



Oers teds disco very . 



(1.) THE analogies that exist between 

 the phenomena of magnetism and those 

 of electricity, in their general character, 

 in the laws which govern them, and in 

 the various combinations they present, 

 are so extensive and so remarkable, as 

 naturally to suggest the notion that the 

 agencies themselves from which they 

 proceed must be allied to one another 

 by some close and intimate relation. 

 Adventurous theorists have advanced 

 the doctrine, that each of these princi- 

 ples is merely a modification of the 

 other, and that both may be regarded 

 as ultimately identical in their nature, 

 constituting, instead of two separate 

 and primary powers, a single power of 

 a higher order of simplicity. 



(2.) The connexion between mag- 

 netism and electricity was a favourite 

 subject of speculation and inquiry 

 among philosophers in the middle of 

 the last century. Many were the efforts 

 made to resolve this seductive problem, 

 which continued, however, to baffle the 

 labours of each succeeding experimen- 

 talist, who multiplied his attempts, and 

 varied his processes, without approach- 

 ing nearer to the point he aimed at ; 

 and also to elude the reasonings of 

 those who theorized upon every new 

 fact until they bewildered both them- 

 selves and their readers in the mazes of 

 visionary and conflicting hypotheses. 



(3.) In the year 1774, the following 

 question was proposed by the Electoral 

 Academy of Bavaria as the subject of 

 a prize dissertation: ' Is there a real 

 and physical analogy between electric 

 and magnetic forces ; and, if such ana- 

 logy exist, in what manner do these 

 forces act upon the animal body?' 

 The essays received by the Academy 

 on that occasion, were collected and 

 published, ten years afterwards, by 

 Professor Van Swinden, of Frantker, 

 the author of one of the essays for 



which the prizes were awarded *. The 

 conclusion to which he arrived, after a 

 long and elaborate discussion of the 

 subject, was, that the similarity between 

 electricity and magnetism amounts 

 merely to an apparent resemblance, 

 and does not constitute a true physical 

 analogy ; whence he infers, that these 

 two powers are essentially different 

 and distinct from one another. The 

 opposite opinion, on the other hand, 

 was maintained by Professors Steigleh- 

 ner and Hubner, who contended that 

 so close an analogy as that exhibited 

 by these two classes of phenomena, in 

 (heated the effects of a single agent, 

 varied only in consequence of a di- 

 versity of circumstances. So many 

 new facts have been brought to light 

 since the time in which these authors 

 wrote, that the reasonings adduced on 

 either side in this controversy have now 

 lost their interest, excepting: that it is 

 still curious to observe by what devious 

 paths they were led away from the 

 truth, at the moment when they had 

 nearly reached it, and when a very slight 

 variation in the form of their experi- 

 ments would at once have disclosed it 

 to their view. 



(4.) Subsequent discoveries relating 

 to the laws of electric and magnetic 

 action, both as respects attraction and 

 repulsion, and also induction, have 

 tended to confirm the analogy between 

 them, and to corroborate the opinion 

 that they ultimately emanate from a 

 common source. Electricity, it is true, 

 affects every species of matter with 

 which we are acquainted, in nearly an 

 equal degree; while magnetism, although 

 perhaps equally universal in its opera- 

 tion, yet acts very feebly, and probably 

 unequally, upon most kinds of matter, 

 and certainly exerts its principal energy 

 upon iron, a circumstance which has, to 



His work is entitled ' Recucil de M^moirea 

 sur 1'Analoi-ie de I'Eleotricitt' et du Magne"tisme 

 couronnes et publics, par i'Acadcmie de Bavi.Ve, 

 &c.' par J. II. Van Swiuden. En trois tomes. Svo 

 A la Haye. 1784. 



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