of its effect[B].

[A] Philosophical Transactions, 1825, p. 481.

[B] This experiment has actually been made by Mr. Christie, with the
results here described, and is recorded in the Philosophical
Transactions for 1827, p. 82.

An elementary result of this kind was obtained by using two pieces of thick
copper, shaped as in fig. 28. When the two neighbouring edges were
amalgamated and put together, and the arrangement passed between the poles
of the magnet, in the direction parallel to these edges, a current was
urged through the wires attached to the outer angles, and the galvanometer
became strongly affected; but when a single film of paper was interposed,
and the experiment repeated, no sensible effect could be produced.

128. A section of this kind could not interfere much with the induction of
magnetism, supposed to be of the nature ordinarily received by iron.

129. The effect of rotation or deflection of the needle, which M. Arago
obtained by ordinary magnets, M. Ampère succeeded in procuring by
electro-magnets. This is perfectly in harmony with the results relative to
volta-electric and magneto-electric induction described in this paper. And
by using flat spirals of copper wire, through which electric currents were
sent, in place of ordinary magnetic poles (Ill.), sometimes applying a
single one to one side of the rotating plate, and sometimes two to opposite
sides, I obtained the induced currents of electricity from the plate
itself, and could lead them away to, and ascertain their existence by, the
galvanometer.