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
hundred 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.

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

10. Two hundred and three feet of copper wire in one length were coiled
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 coil, and
metallic contact everywhere prevented by twine. One of these helices was
connected with a galvanometer, and the other with a battery of one 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 nor 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.

11. 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 the former time, that the slight deflection of the needle
occurring at the moment of completing the connexion, was always in one