92 



wire, induced a similar current through the other wire, but only at 

 the moment the contact was made; and a current in the contrary 

 direction when the passage of the electricity was suddenly inter- 

 rupted. These transitory currents, resembling waves, were found to 

 be capable of magnetizing needles placed within the helix. Colla- 

 teral currents, either in the same or in opposite directions, exert no 

 permanent inductive power on each other. 



No other evidence of the electric action of these induced currents 

 could be detected, such as the appearance of a spark, the ignition of 

 fine wires, or of charcoal, impressions on the tongue, contractions in 

 the muscles of frogs, or chemical decompositions. Yet these induced 

 currents were found to be capable of passing through fluids, when 

 interposed to a small extent in the circuit. 



Similar effects were apparently produced by the inductive influence 

 of ordinary electricity directed through the first set of wires. 



The second part of this paper contains the account of experi- 

 ments in which the helix connected with the voltaic battery was 

 wound round one side of an iron ring, welded from soft round bar- 

 iron ; while another helix connected with a galvanometer was coiled 

 round the opposite side of the ring. The electrical indications ob- 

 tained by this apparatus were much more considerable than in the 

 former case, but were equally transitory, and were of opposite kinds 

 on the interruption of the contacts with the battery. By interposing 

 charcoal points in the circuit of the induced helix, a minute spark 

 was perceived whenever the contacts were made or broken off; but 

 no ignition of wires or other electric effects could be obtained. 

 Electric currents were also induced in a helix into which a soft iron 

 cylinder was introduced, whenever that iron was rendered magne- 

 tical by induction from magnets applied to its ends. The sudden 

 introduction or removal of a magnet, in the place of the iron cylin- 

 der, produced similar effects on the helix. 



In many of these experiments the author employed the large com- 

 pound magnet constructed by Dr. Gowin Knight, and belonging to 

 the Royal Society. Similar effects were produced when the iron was 

 surrounded by a piece of copper plate wrapped once round it with its 

 edges connected with the wires of the galvanometer. Currents were 

 induced on a wire coiled into a flat spiral, by bringing one of the 

 poles of the powerful magnet of Dr. Knight opposite to its centre. 

 Even single wires brought near the pole of this magnet had electric 

 currents induced in them. But all attempts to obtain chemical 

 effects by these currents of electricity induced by magnetism were 

 unsuccessful. 



In the third part of the paper the author regards the condition 

 in which a conducting wire exists while it is subject either to volta- 

 electric, or magneto-electric induction, as a peculiar one, which he 

 designates by the term Electro-tonic state. This peculiar condition 

 shows no electrical effects while it continues, nor does it exert any 

 sensible action on matter, or on other electrical currents, either of 

 an attractive or repulsive kind; nor does it tend either to accele- 

 rate or to retard those currents. 



