466 Dr. Faraday's Researches in Electricity. 



citing wire helix. On sending an electric current through the 

 helix, both it and the magnet it produces will conduce to the 

 formation of currents in the copper bar in the contrary direc- 

 tion. This is shown from my former researches (26.), and 

 may be proved, by placing a small or large wire helix-shaped 

 (if it be desired) in the form of the bar, and carrying away the 

 currents produced in it, by wires to a galvanometer at a dis- 

 tance. Such currents being produced in the copper, only 

 continue whilst the magnetism of the core is rising and then 

 . cease (18. 39.), but whilst they continue, they give a virtual 

 magnetic polarity to that face of the copper bar which is op- 

 posite to a certain pole, the polarity being the same in kind as 

 the pole it faces. Thus on the side of the bar facing the 

 north pole of the magnet, a north polarity will be developed ; 

 and on that side facing the south pole, a south polarity will be 

 generated. 



2334. It is easy to see that if the copper during this time 

 were opposite only one pole, or being between two poles, were 

 nearer to one than the other, this effect would cause its repul- 

 sion. Still, it cannot account for the whole amount of the re- 

 pulsion observed alike with copper as with bismuth (2295.), 

 because the currents are of but momentary duration, and the 

 repulsion due to them would cease with them. They do, 

 however, cause a brief repulsive effort, to which is chiefly due 

 the first part of the peculiar effect. 



2335. For if the copper bar, instead of being parallel to 

 the face of the magnetic pole, and therefore at right angles to 

 the resultant of magnetic force, be inclined, forming, lor in- 

 stance, an angle of 45° with the face, then the induced currents 

 will move generally in a plane corresponding more or less to 

 that angle, nearly as they do in the examining helix (2333.), 

 if it be inclined in the same manner. This throws the polar 

 axis of the bar of copper on one side, so that the north polarity 

 is not directly opposed to the north pole of the inducing mag- 

 net, and hence the action both of this and the other mag- 

 netic pole upon the two polarities of the copper will be to send 

 it further round, or to place it edgeways to the poles, or with 

 its breadth parallel to the magnetic resultant passing through 

 it (2323.) : the bar therefore receives an impulse, and the angle 

 of it nearest to the magnet appears to be pulled up towards 

 the magnet. This action of course stops the instant the mag- 

 netism of the helix core ceases to rise, and then the motion 

 due to this cause ceases, and the copper is simply subject to 

 the action before described (2295.). At the same time that 

 this twist or small portion of a turn round the point of sus- 

 pension occurs, the centre of gravity of the whole mass is re- 



