358 ' ROTATION BY ELECTKICITY. [SECT. xxxi. 



same quantity of electricity, and that they deflect the mag- 

 netic needle in an equal degree, when their respective axes 

 of conduction are at the same distance from it. But one of 

 the most extraordinary effects of the new force is exhibited 

 by coiling a copper wire, so as to form a helix or corkscrew, 

 and connecting the extremities of the wires with the poles 

 of a galvanic battery. If a magnetized steel bar or needle 

 be placed within the screw, so as to rest upon the lower part, 

 the instant a current of electricity is sent through the wire 

 of the helix, the steel bar starts up by the influence of this 

 invisible power, and remains suspended in the air in oppo- 

 sition to the force of gravitation (N. 218). The effect of 

 the electro-magnetic power exerted by each turn of the wire 

 is to urge the north pole of the magnet in one direction, and 

 the south pole in the other. The force thus exerted is mul- 

 tiplied in degree and increased in extent by each repetition 

 of the turns of the wire, and in consequence of these opposing 

 forces the bar remains suspended. This helix has all the 

 properties of a magnet while the electrical current is flowing 

 through it, and may be substituted for one in almost every 

 experiment. It acts as if it had a north pole at one ex- 

 tremity and a south pole at the other, and is attracted and 

 repelled by the poles of a magnet exactly as if it were one 

 itself. All these results depend upon the course of the elec- 

 tricity ; that is, on the direction of the turns of the screw, 

 according as it is from right to left, or from left to right, 

 being contrary in the two cases. 



The action of Voltaic electricity on a magnet is not only 

 precisely the same with the action of two magnets on one 

 another, but its influence in producing temporary magnet- 

 ism in iron and steel is also the same with magnetic induction. 

 The term induction, when applied to electric currents, 

 expresses the power which these currents possess of inducing 

 any particular state upon matter in their immediate neigh- 

 bourhood, otherwise neutral or indifferent. For example, 

 the connecting wire of a galvanic battery holds iron filings 



