MICHAEL FARADAY 195 



28. The helix B, was connected by copper wires with a galva- 

 nometer three feet from the ring. The helices of A were connected 

 end to end so as to form one common helix, the extremities of which 

 were connected with a battery of ten pairs of plates four inches square. 

 The galvanometer was immediately affected, and to a degree far be- 

 yond what has been described when with a battery of tenfold power 

 helices without iron were used (10) ; but though the contact was con- 

 tinued, the effect was not permanent, for the needle soon came to rest 

 in its natural position, as if quite indifferent to the attached electro- 

 magnetic arrangement. Upon breaking the contact with the battery, 

 the needle was again powerfully deflected, but in the contrary direction 

 to that induced in the first instance. 



29. Upon arranging the apparatus so that B should be out of use, 

 the galvanometer be connected with one of the three wires of A (27), 

 and the other two made into a helix through which the current from 

 the trough (28) was passed, similar but rather more powerful effects 

 were produced. 



30. When the battery contact was made in one direction, the gal- 

 vanometer-needle was deflected on the one side ; if made in the other 

 direction, the deflection was on the other side. The deflection on 

 breaking the battery contact was always the reverse of that produced 

 by completing it. The deflection on making a battery contact always 

 indicated an induced current in the opposite direction to that from the 

 battery ; but on breaking the contact the deflection indicated an in- 

 duced current in the same direction as that of the battery. No mak- 

 ing or breaking of the contact at B side, or in any part of the 

 galvanometer circuit, produced any effect at the galvanometer. No 

 continuance of the battery current caused any deflection of the galva- 

 nometer-needle. As the above results are common to all these 

 experiments, and to similar ones with ordinary magnets to be here- 

 after detailed, they need not be again particularly described. 



31. Upon using the power of 100 pairs of plates (10) with this 

 ring, the impulse at the galvanometer, when contact was completed or 

 broken, was so great as to make the needle spin round rapidly four or 

 five times, before the air and terrestrial magnetism could reduce its 

 motion to mere oscillation. 



39. But as might be supposed that in all the preceding experiments 

 of this section, it was by some peculiar effect taking place during the 



