33. A feeble voltaic current was sent through the helix B and the
galvanometer, so as to deflect the needle of the latter 30° or 40°, and
then the battery of one hundred pairs of plates connected with A; but after
the first effect was over, the galvanometer-needle resumed exactly the
position due to the feeble current transmitted by its own wire. This took
place in whichever way the battery contacts were made, and shows that here
again (20.) no permanent influence of the currents upon each other, as to
their quantity and tension, exists.

34. Another arrangement was then employed connecting the former experiments
on volta-electric induction (6-26.) with the present. A combination of
helices like that already described (6.) was constructed upon a hollow
cylinder of pasteboard: there were eight lengths of copper wire, containing
altogether 220 feet; four of these helices were connected end to end, and
then with the galvanometer (7.); the other intervening four were also
connected end to end, and the battery of one hundred pairs discharged
through them. In this form the effect on the galvanometer was hardly
sensible (11.), though magnets could be made by the induced current (13.).
But when a soft iron cylinder seven eighths of an inch thick, and twelve
inches long, was introduced into the pasteboard tube, surrounded by the
helices, then the induced current affected the galvanometer powerfully and
with all the phenomena just described (30.). It possessed also the power of
making magnets with more energy, apparently, than when no iron cylinder was
present.

35. When the iron cylinder was replaced by an equal cylinder of copper, no
effect beyond that of the helices alone was produced. The iron cylinder
arrangement was not so powerful as the ring arrangement already described
(27.).