and OH the Theory of Magnetism. 79 



Having succeeded thus far, I endeavoured to make a wire 

 and a magnet revolve on their own axis by preventing the rota- 

 tion in a circle round them, but have not been able to get the 

 slightest indications that such can be the case; nor does it, on 

 consideration, appear probable. The motions evidently belong 

 to the current, or whatever else it be, that is passing through the 

 wire, and not to the wire itself, except as the vehicle of the cur- 

 rent. When that current is made a curve by the form of the wire, 

 it is easy to conceive how, in revolving, it should take the 

 wire with it ; but when the wire is straight, the current may re- 

 volve without any motion being communicated to the wire 

 through which it passes. 



M. Ampere has shewn that two similar connecting wires, by 

 which is meant, having currents in the same direction through 

 them, attract each other ; and that two wires having currents in 

 opposite directions through them, repel each other ; the attraction 

 and repulsion taking place in right lines between them. From 

 the attraction of the north pole of a needle on one side the wire 

 and of the south on the other, and the repulsion of the poles on 

 the opposite sides. Dr. Wollaston called this magnetism verti- 

 ginous, and conceived that the phsenomena might be explained 

 upon the supposition of an electro-magnetic current passing 

 round the axis of the conjunctive wire, its direction depending 

 upon that of the electric current, and exhibiting north and south 

 powers on the opposite sides. It is, indeed, an ascertained 

 fact, that the connecting wire has different powers at its opposite 

 sides ; or rather each power continues all round the wire, the 

 direction being the same ; and hence it is evident that the at- 

 tractions and repulsions of M. Ampere's wires are not simple, 

 but complicated results. 



A simple case which may be taken of magnetic motion, is the 

 circle described by the wire or the pole round each other. If 

 a wire be made into a helix, as M. Ampere describes, the 

 arrangement is such that all the vertiginous magnetism, as Dr. 

 Wollaston has named it, of the one kind, or one side of the wire, 

 is concentrated in the axis of the helix, whilst the contrary kind 

 is very much diffused, t. e., the power exerted by a great length 



