and on the Theory of Magnetism. BS 



^lace, and when dissimilar, attraction ; so that two cases of 

 repulsion and one of attraction are produced by the combination 

 of these magnetic powers *. 



The next cases of magnetic motion, in the order of simplicity, 

 are those where three powers are concerned or those produced 

 by a pole and a wire. These are the circular motions de- 

 scribed in the early part of this paper. They .resolve them- 

 selves into two, a north pole and the wire round each other, 

 and a south pole, and the wire round each othef. The law 

 which governs these motions has been stated. 



Then follow the actions between two wires, these when simi- 

 larly electrified attract as M. Ampere has shewn ; for then the 

 opposite sides are towards each other, and the four powers all 

 combine to draw the currents together forming a double at- 

 traction; but, when the wires are dissimilar they repel, because, 

 then on both sides the wire the same powers are opposed, 

 and cause a double repulsion. 



The motions that result from the action of two dissimilar 

 poles and a wire next follow: the wire endeavours to describe 

 opposite circles round the poles ; consequently, it is carried 

 in a line passing through the central part of the needle in which 

 they are situated. If the wire is on the side on which the circles 

 ■close together, it is attracted ; If on the opposite side, from 

 whence the circles open, it is repelled, fig. 10. 



The motions of a pole with two wires are almost the same 

 as the last ; when the wires are dissimilar, the pole endeavours 

 to form two opposite circles about the wires ; when it is on that 

 side the wires on which the circles meet, it is attracted ; when 

 on the side on which they open, it is repelled, figs. 8, 11, 12. 



Finally, the motion between two poles and two dissimilar 

 wires, is an instance where several powers combine to produce 

 an effect. 



M. Ampere, whilst reasoning on the discovery of M. Oersted, 

 was led to the adoption of a theory, by which he endeavoured 

 to account for the properties of magnets, by the existence of 



• J'liis ig perhaps not strictly true, because, though the opposite powei» 

 iut weakeuotl.they still remain inaction. 



