Experimental Researches in Electricity, S 



enter into any of the details of this, forms no part of our pre- 

 sent design, save in so far as it may be necessary to ensure a 

 clear apprehension of the views we shall subsequently ex- 

 press ; and we may therefore only briefly state at present, 

 that on analysing the experiments of Oersted into their sim- 

 plest conditions, it appeared as if the conducting wire exert- 

 ed on the pole of the magnet a kind of force, neither attrac- 

 tive nor repulsive, but transverse ; and by numerous experi- 

 ments it was clearly established that the force was really of 

 this perfectly novel and singular nature, a remarkable ex- 

 ample of it being exhibited by Mr. Faraday in 1821, 

 wherein the force actually sustained either the wire or the 

 magnet, in a state of constant and rapid revolution about 

 each other. Two theories were proposed in explanation of 

 these phenomena, the one by Oersted, in which the conduct- 

 ing wire was supposed to be made up of an infinite number 

 of minute transverse magnets, having their opposite poles 

 facing each other ; and the other devised by M. Ampere, in 

 which the magnet is supposed to be made up of a series of 

 conducting wires in transverse positions. At first sight it 

 seemed a matter of indifference which of the two theories 

 was selected, as both appeared capable of application to the 

 facts : but it was ere long found that the first could not, with- 

 out certain arbitrary and improbable additions, afford any 

 explanation of continued motion in electro-magnetic experi- 

 ments, while the second explained this, and also the mutual 

 action of magnets on each other, and of conducting wires on 

 each other, cases not contemplated by Ampere in originally 

 devising his theory, and therefore telling strongly in its 

 favour, in the most complete and satisfactory manner. Re- 

 markable experimental evidence for the Amperian theory 

 was farther obtained from the perfect identity of effects 

 produced by spiral conducting wires, or electro-dynamic 

 cylinders as they were called, and common magnets. In com- 

 mon they are influenced by the magnetism of the earth ; the 



