126 MR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 
cuiTent induced through them, or some sensible effect produced equivalent in 
force to such a current. 
4. These considerations, with their consequence, the hope of obtaining elec- 
tricity from ordinary magnetism, have stimulated me at various times to inves- 
tigate experimentally the inductive effect of electric currents. I lately arrived 
at positive results ; and not only had my hopes fulfilled, but obtained a key 
which appeared to me to open out a full explanation of Arago’s magnetic phe- 
nomena, and also to discover a new state, which may probably have great 
influence in some of the most important effects of electric currents. 
5. These results I purpose describing, not as they were obtained, but in such 
a manner as to give the most concise view of the whole. 
§. 1. Induction of Electric Currents. 
6. About twenty-six feet of copper wire one twentieth of an inch in diameter 
were wound round a cylinder of wood as a helix, the different spires of which 
were prevented from touching by a thin interposed twine. This helix was 
covered with calico, and then a second wire applied in the same manner. 
In this way twelve helices were superposed, each containing an average length 
of wire of twenty-seven feet, and all in the same direction. The first, third, 
fifth, seventh, ninth, and eleventh of these helices were connected at their ex- 
tremities end to end, so as to form one helix ; the others were connected in 
a similar manner ; and thus two principal helices were produced, closely inter- 
posed, having the same direction, not touching anywhere, and each containing 
one hundred and fifty-five feet in length of wire. 
7. One of these helices was connected with a galvanometer, the other with a 
voltaic battery of ten pairs of plates four inches square, with double coppers 
and well charged ; yet not the slightest sensible deflection of the galvanometer 
needle could be observed. 
8. A similar compound helix, consisting of six lengths of copper and six of 
soft iron wire, was constructed. The resulting iron helix contained two hun- 
dred and fourteen feet of wire, the resulting copper helix two hundred and 
eight feet ; but whether the current from the trough was passed through the 
copper or the iron helix, no effect upon the other could be perceived at the 
galvanometer. 
