ion should, if simultaneously
stopped, aid each other by their relative influence; or if proceeding in
contrary directions, should oppose each other under similar circumstances.
I endeavoured at first to obtain two currents from two different
electromotors, and passing them through the helices i and ii, tried to
effect the disjunctions mechanically at the same moment. But in this I
could not succeed; one was always separated before the other, and in that
case produced little or no spark, its inductive power being employed in
throwing a current round the remaining complete circuit (1090.): the
current which was stopped last always gave a bright spark. If it were ever
to become needful to ascertain whether two junctions were accurately broken
at the same moment, these sparks would afford a test for the purpose,
having an infinitesimal degree of perfection.

1098. I was able to prove the points by other expedients. Two short thick
wires were selected to serve as terminations, by which contact could be
made or broken with the electromotor. The compound helix, consisting of i
and ii (1053.), was adjusted so that the extremities of the two helices
could be placed in communication with the two terminal wires, in such a
manner that the current moving through the thick wires should be divided
into two equal portions in the two helices, these portions travelling,
according to the mode of connexion, either in the same direction or in
contrary directions at pleasure. In this manner two streams could be
obtained, both of which could be stopped simultaneously, because the
disjunction could be broken at G or F by removing a single wire. When the
helices were in contrary directions, there was scarcely a sensible spark at
the place of disjunction; but when they were in accordance there was a very
bright one.

1099. The helix i was now used constantly, being sometimes associated, as
above, with helix ii in an according direction, and sometimes with helix
iii, which was placed at a little distance. The association i and ii, which
presented two currents able to affect each other by induction, because of
their vicinity, gave a brighter spark than the association i and iii, where
the two streams could not exert their mutual influence; but the difference
was not so great as I expected.

1100. Thus all the phenomena tend to prove that the effects are due to an
inductive action, occurring at the moment when the principal current is
stopped. I