ELECTRO-MAGNETISM. 



the true connexion between magnetism 

 and electricity. 



CHAPTER II. 



Account of Oersted's Experiments. 



(9.) The real discoverer of the mag- 

 netic properties of electric currents was 

 M. Oersted, Professor of Natural Phi- 

 losophy, and Secretary to the Royal 

 Society of Copenhagen. In a work 

 which he published in German, about 

 the year 1813, on the identity of chemi- 

 cal and electrical forces *, he had thrown 

 out conjectures concerning the relations 

 subsisting between the electric, galvanic, 

 and magnetic fluids, which he conceived 

 might differ from one another only in 

 their respective degrees of tension. If 

 galvanism, he argued, be merely a more 

 latent form of electricity, so magnetism 

 may possibly be nothing more than elec- 

 tricity in a still more latent form ; and 

 he therefore proposed it as a subject 

 worthy of inquiry whether electricity, 

 employed in this, its most latent form, 

 might not be found to have a sensible 

 effect upon a magnet. It is difficult 

 clearly to understand what he means by 

 the expression of latent states, as ap- 

 plied to electricity, but it may be suffi- 

 cient for us to know that in the various 

 endeavours he subsequently made to 

 verify his conjectures, he was led to 

 such forms of experiment as afforded 

 decisive indications of the influence of 

 Voltaic currents on the magnetized 

 needle. Yet, even after he had suc- 

 ceeded thus far, it was a matter of ex- 

 treme difficulty to determine the real 

 direction of this action, and it was not 

 till the close of the year 1819 that his 

 perseverance was at length rewarded by 

 complete success. 



(10.) The first account of his disco- 

 very that appeared in England is con- 

 tained in a paper, which he himself 

 communicated, in Thomson's Annals of 

 Philosophy, for October, 1820f; and 

 in which the following experiments are 

 described : The two poles of a powerful 

 Voltaic battery were connected by a 

 metallic wire, so as to complete the gal- 

 vanic circuit. The wire which performs 

 this office he called the uniting wire ; 

 and the effect, whatever it may be, which 

 takes place in this conductor, and in the 

 space surrounding it, during the pas- 



* This work was translated into French by 

 Marcel des Serres, under the title of ' Reoherches 

 stir 1'ldentite des Forces Chimiqnes et Electriques. 

 I'aris 1813.' See the 8th Chapter of that work. 



t Vol. XVI. of the first series, p. 273. 



sage of the electricity, he designates by 

 the term electric conflict, from an idea 

 that there takes place some continued 

 collision and neutralization of the two 

 species of electric fluids, while circulat- 

 ing in opposite currents in the appara- 

 tus. Then taking a magnetic needle, 

 properly balanced on its pivot, as in the 

 mariner's compass, 'and allowing it to 

 assume its natural position in the mag- 

 netic meridian, he placed a straight 

 portion of the uniting wire horizontally 

 above the needle, and in a direction 

 parallel to it ; and then completed tha 

 circuit, so that the electric current passed 

 through the wire. The moment this 

 was done, the needle changed its position, 

 its ends deviating from the north ami 

 south towards the east or west, accord- 

 ing to the direction in which the electric 

 current flowed, so that by reversing the. 

 direction of the current the motion of 

 the needle was also reversed. The ge- 

 neral law he expressed as follows : 

 * That end of the needle which is si- 

 tuated next to the negative side of the 

 battery, or towards which the current 

 of positive electricity is flowing, imme- 

 diately moves to the westward.' 



(11.) The deviation of the needle is 

 the same, whether the uniting wire, in- 

 stead of being immediately above the 

 needle, be placed somewhat to the east 

 or west of it, provided it continue pa- 

 rallel to and also above it. This shows, 

 that the effect is not the result of a sim- 

 ple attractive or repulsive influence, fear 

 the same pole of the magnetic needle 

 which approaches the uniting wire when 

 placed on its east side recedes from it 

 when placed on its west side. 



(12.) If the uniting wire be placed in 

 a horizontal plane under the magnetic- 

 needle the latter is affected to an equal 

 degree as in the former case, but the 

 motions are made in the contrary di- 

 rection ; for the pole of the needle next 

 to the negative end of the battery now 

 deviates towards the east. 



(13.) The effects above described will 

 Fig. 1. 





