and on the Theortf of Magnetism. 81 



which is some mercury with which to connect the wires. In 

 describing them I shall refrain from entering into all their vari- 

 ations, or pursuing them to such conclusions as are not directly 

 important. 



Two similar wires, Ampere has shewn, attract each other ; and 

 Sir H. Davy has shewn that the filings adhering to them attract 

 from one to another on the same side. They are in that 

 position in which the north and south influence of the different 

 wires attract each other. They seem also to neutralize each 

 other in the parts that face, for the magnetic pole is quite 

 inactive between them, but if put close together, it moves 

 round the outside of both, circulating round them as round 

 one wire, and their influences being in the same direction? 

 the greatest effect is found to be at the farther outside sur- 

 faces of the wires. If several similar wires be put together, 

 side by side like a ribbon, the result is the same, and the 

 needle revolves round them all ; the internal wires appear to 

 lose part of their force, which is carried on towards the 

 extreme wire in opposite directions, so that the floating pole 

 is accelerated in its motion as it passes by the edges that they 

 form. If, in place of a ribbon of parallel wires, a slip of metal 

 be used, the effect is the same, and the edges act as if they 

 contained in a concentrated state the power that belonged to the 

 inner portion of the slip. In this way we procure the means 

 of removing, as it were, in that direction, the two sides of the wire 

 from each other. 



If two wires in opposite states be arranged parallel to eaph 

 other, and the pole be brought near them, it will circulate 

 round either of them in obedience to the law laid down ; but 

 as the wires have opposite currents, it moves in opposite direc- 

 tions round the two, so that when equidistant from them, 

 the pole is propelled in a right line perpendicular to the 

 line which joins them, either receding or approaching; and 

 if it approaches, passing botween and then receding : hence 

 it exhibits the curious appearance of being first attracted by 

 the two wires, and afterwards repelled. (Fig. 8.) If the con- 



VoL. Xll. G 



