the line of expectation, came into play--he noticed that a feeble movement of the needle always occurred at the moment when he made contact with the battery; that the needle would afterwards return to its former position and remain quietly there unaffected by the flowing current. At the moment, however, when the circuit was interrupted the needle again moved, and in a direction opposed to that observed on the completion of the circuit. This result, and others of a similar kind, led him to the conclusion 'that the battery current through the one wire did inreality induce a similar current through the other; but that it continued for an instant only, and partook more of the nature ofthe electric wave from a common jar than of the current from a voltaic battery.' The momentary currents thus generated were called induced currents, while the current which generated them was called the inducing current. It was immediately proved that the current generated at making the circuit was always opposed in direction to its generator, while that developed on the rupture of the circuit coincided in direction with the inducing current. It appeared as if the current on its first rush through the primary wire sought a purchase in the secondary one, and, by a kind of kick, impelled backward through the latter an electric wave, which subsided as soon as the primary current was fully established.Faraday, for a time, believed that the secondary wire, though quiescent when the primary current had been once established, was not in its natural condition, its return to that condition being declared by the current observed at breaking the circuit. He called this hypothetical state of the wire the electrotonic state: he afterwards abandoned this hypothesis, but seemed to return to it in later life. The term electrotonic is also preserved by Professor Du Bois Reymond to express a certain electric condition of the nerves.The mere approach of a wire forming a closed c...
