EVOLUTION OF ELECTRICITY FROM MAGNETISM. 
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from the voltaic battery, volta-electric induction. The properties of the wire, 
after induction has developed the first current, and whilst the electricity from 
the battery continues to flow through its inducing neighbour (10. 18.), consti- 
tute a peculiar electric condition, the consideration of which will be resumed 
hereafter. All these results have been obtained with a voltaic apparatus con- 
sisting of a single pair of plates. 
§ 2. Evolution of Electricity from Magnetism. 
27- A welded ring was made of soft round bar-iron, the metal being seven 
eighths of an inch in thickness, and the ring six inches in external diameter. 
Three helices were put round one part of this ring, each containing about 
twenty-four feet of copper wire one twentieth of an inch thick ; they were in- 
sulated from the iron and each other, and superposed in the manner before 
described (6.), occupying about nine inches in length upon the ring. They could 
be used separately or arranged together ; the group may be distinguished by the 
mark A (PI. III. fig. 1.). On the other part of the ring about sixty feet of similar 
copper wire in two pieces were applied in the same manner, forming a helix B, 
which had the same common direction with the helices of A, but being sepa- 
rated from it at each extremity by about half an inch of the uncovered iron. 
28. The helix B was connected by copper wires with a galvanometer three 
feet from the ring. The wires of A were connected end to end so as to form 
one long 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 beyond what has been described, when with a battery of 
tenfold power helices without iron were used (10.) ; but though the contact was 
continued, 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 galva- 
nometer be connected with one of the three wires of A, 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. 
s 2 
