SECT, xxxiii.] MAGNETO-ELECTRICITY. 365 



SECTION XXXIII. 



Magneto-Electricity Volta-Electric Induction Magneto-Electric Induction- 

 Identity in the Action of Electricity and Magnetism Description of a 

 Magneto-Electric Apparatus and its Effects Identity of Magnetism and 

 Electricity. 



FROM the law of action and reaction being equal and con- 

 trary, it might be expected that, as electricity powerfully 

 affects magnets, so, conversely, magnetism ought to produce 

 electrical phenomena. By proving this very important fact 

 from the following series of interesting and ingenious experi- 

 ments, Dr. Faraday has added another branch to the science 

 which he has named magneto-electricity. A great quantity 

 of copper wire was coiled in the form of a helix round one 

 half of a ring of soft iron, and connected with a galvanic bat- 

 tery ; while a similar helix connected with a galvanometer 

 was wound round the other half of the ring, but not touching 

 the first helix. As soon as contact was made with the battery, 

 the needle of the galvanometer was deflected. But the action 

 was transitory; for, when the contact was continued, the needle 

 returned to its usual position, and was not affected by the 

 continual flow of the electricity through the wire connected 

 with the battery. As soon, however, as the contact was broken, 

 the needle of the galvanometer was again deflected, but in the 

 contrary direction. Similar effects were produced by an ap- 

 paratus consisting of two helices of copper wire coiled round 

 a block of wood, instead of iron, from which Dr. Faraday in- 

 fers that the electric current passing from the battery through 

 one wire induces a similar current through the other wire, 

 but only at the instant of contact, and that a momentary cur- 

 rent is induced in a contrary direction when the passage of 

 the electricity is suddenly interrupted. These brief currents 

 or waves of electricity were found to be capable of magnetiz- 



