114 Historical Sketch of Electrch-magtietism. [Feb, 



that power exhibited by the other side of the wire in the other 

 end. 



On takino- away the remaining wire, and substituting a second 

 magnet for it, the two acted in the usual manner ; but the action 

 was found to be analogous to that of two electrical currents. 

 So that M. Ampere was forced by his experiments, and the view 

 he had taken of them, to conclude, that all the attractions, 

 whether excited by two wires, a wire and a magnet, or two 

 magnets, were purely electrical, and, in fine, that all magnetic 

 phenomena are occasioned by electric currents. 



Taken in this point of view, electricity and magnetism are 

 identical, or rather, magnetic phenomena are a series of electri- 

 cal phenomena. Hence magnetism should form a branch of 

 electricity under the head of electrical currents; but before we 

 dispose of it in this premature, though convenient, manner, we 

 should endeavour to state what the arrangement of electrical 

 currents are which M. Ampere has found it necessary to assume 

 to account for the various known phenomena of magnetism. 



The arrangement of magnetic power in a conducting wire is 

 so different to that in a magnet, that it is not at first very evident 

 how the one may be considered as convertible into the other. 

 Currents of electricity, according to the theory, were essentially 

 necessary to the production of magnetic phenomena, but where 

 are the currents in a common magnet ? It was a bold thought to 

 say they actually existed in it, but M. Ampere has ventured the 

 idea, and has so arranged them, theoretically, as to account for 

 very many magnetic phenomena. 



A magnet, M. Ampere says, is an assemblage of as many 

 electric currents moving in planes perpendicular to the axis, as 

 there may be conceived fines, which, without cutting each other, 

 form closed curves ; for, he says, it seems impossible to him 

 from the simple cofiisideration of the facts, to doubt that there 

 are really such currents round the axes of magnets ; and magne- 

 tization consists, he says, in an operation by which there is given 

 to the particles of steel the property of producing in the direc- 

 tion of the currents before spoken of, the same electromotive 

 action which is found in the voltaic pile, the electric calamine 

 of mineralogists, the heated tourmaline, and .even in the pile 

 formed of moistened paper, and discs of the same metal at 

 different temperatures. 



With regard to the extent of the curves which these currents 

 travel through, the theory has not yet decided whether it relates 

 to the whole magnet, or to the particles of which it is formed. 

 If a section of a magnet perpendicular to its axis be conceived, 

 the currents situated in it may either be concentric, in which 

 case they will vary gradually in extent, or they may exist round 

 each particle, in wnich case they are of uniform size, but very 

 minute. It appears from calculation that either of these arrange- 



