That a powerful voltaic pile is required for these experiments (of
Oersted) I have confirmed in my physics lectures, using an electric
pile that was so strong it would easily produce potassium metal the
second and third day after it was built. However, I soon saw that
the electromagnetic effect was related, not to the pile, but to the
simple circuit, and I was thereby led to perform the experiment with
much greater sensitivity. To amplify these electromagnetic phenomena
of the simple circuit it seemed to me necessary to adopt a different
arrangement from that initiated by Volta, in order that the
electrical phenomena of his simple circuit might be raised to a
higher degree.
Since a reversal of the effect occurs according to whether the
connecting-wire lies over or under the needle, and likewise
according to whether the wire leads from the positive or negative
pole, thence I say it is an easy inference that a doubling of the
effect is attainable, which is verified in practice.
I present to the Society the simple "doubling apparatus"
[_Verdoppelungs-Apparat_], where the compass is placed between two
wires passing around it. A multiplication of the effect is easily
obtained when the wire is not just once but many times wound around.
A single turn suffices, however, to demonstrate Oersted's
experiments, using small strips of zinc and copper dipped in
ammonium-chloride solution.
Amid innumerable, rambling theorizations (such as, that "hydrogenation
affects magnetism as oxidation affects galvanism," or "sulphur,
phosphorous and carbon are especially significant in magnetism, since
iron in combination with any of these inflammable materials becomes a
magnet-material"), Schweigger announces that he looked for the reactive
force of the needle on the connecting wire in the simple Oersted
experiment, and that he used his "amplifying apparatus" to look for
magnetic effects from an electrostatic machine, but without success in
both cases. He suggests that he will continue with many more
electromagnetic experiments because "with the use of the
doubling-apparatus, the needle, instead of needing for excitation a cell
capable of generating sparks, approaches more closely the sensitivity of
a twitching nerve." However, "additional special experiments are
required to find to what limits the amplification can be increased by
the method I have created in the construction of this
doubling-apparatus, using multiple turns of wire."
[Illustration: Figure 3.--THIS WIRE "BOW-PATTERN" was the first
illustration Schweigger gave of his "doubling apparatus," though he had
presented a verbal description of a single-coil arrangement somewhat
earlier. The purpose of the bow pattern was to show that compass needles
at the centers of the two loops deflected in opposite directions. (From
_Journal für Chemie und Physik_.)]