322 MAGNETO-ELECTRICITY. SECT. XXXII. 



SECTION XXXII. 



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

 tion Identity in the Action of Electricity and Magnetism Descrip- 

 tion of a Magneto-Electric Apparatus and its Effects Identity of 

 Magnetism and Electricity The Submarine Telegraph. 



FROM the law of action and reaction being equal and contrary, 

 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 fol- 

 lowing series of interesting and ingenious experiments, Dr. Fara- 

 day 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 battery ; while a similar helix con- 

 nected 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 con- 

 tinued, 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 apparatus consisting of two helices of copper wire coiled 

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

 infers 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 current is 

 induced in a contrary direction when the passage of the electricity 

 is suddenly interrupted. These brief currents or waves of elec- 

 tricity were found to be capable of magnetizing needles, of pass- 

 ing through a small extent of fluid, and, when charcoal points 

 were interposed in the current of the induced helix, a minute 

 spark was perceived as often as the contacts were made or 



