ed 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.

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.

"A similar compound helix, consisting of six lengths of copper and six
of soft iron wire, was constructed. The resulting iron helix contained
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.

"In these and many similar experiments no difference in action of any
kind appeared between iron and other metals.

"Two hundred and three feet of copper wire in one length were passed
round a large block of wood; other two hundred and three feet of similar
wire were interposed as a spiral between the turns of the first, and
metallic contact everywhere prevented by twine. One of these helices was
connected with a galvanometer and the other with a battery of a hundred
pairs of plates four inches square, with double coppers and well
charged. When the contact was made, there was a sudden and very slight
effect at the galvanometer, and there was also a similar slight effect
when the contact with the battery was broken. But whilst the voltaic
current was continuing to pass through the one helix, no galvanometrical
appearances of any effect like induction upon the other helix could be
perceived, although the active power of the battery was proved to be
great by its heating the whole of its own helix, and by the brilliancy
of the discharge when made through charcoal.

"Repetition of the experiments with a battery of one hundred and twenty
pairs of plates produced no other effects; but it was ascertained, both
at this and at the former time, that the slight deflection of the needle
occurring at the moment of completing the connection was always in one
direction, and that the equally slight deflection produced when the
contact was broken was in the other direction; and, also, that these
effects occurred when the first helices were used.

"The results which I had by this time obtained with magnets led me
to believe that the battery current thr