Original Electromagnetic Multipliers Of the three sets of instruments made, respectively, by Schweigger, Poggendorf and Cumming, those of Schweigger are the most elementary, and the least realistic from a practical point of view. He makes little effort to investigate the effect of any design parameters, but presents some odd conductor configurations that involve unimportant variations of the basic principle. The following extracts from his first three papers[13] contain the major references to his conception, construction, and use of his multiplier. PAPER READ IN HALLE, SEPTEMBER 16, 1820 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.