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 phenomena, 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 extremities 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 interposed, 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 reflection of the
galvanometer-needle could be observed.