Conclusions

The multiple surrounding of the needle by a silk-covered wire, in a plane perpendicular to the long axis of the needle, affords the physicist a very simple and sensitive means of detecting the slightest trace of galvanism, or of magnetism produced by it, so that I have given the name of magnetic condenser to this construction, though I attach no special value to this name ...In analyzing the astonishingly increased power which the condenser gives to the magnetic effect of a circuit, the first question that arises is how the effect varies with the number of turns, whether it increases indefinitely or reaches a maximum beyond which additional turns have no effect. The answer to this first question is linked to the solution of another, viz, whether the degrees deflection are a direct expression of the measure of the magnetic force or not.To instruct myself on this point I made use of three separate circuits, each containing an 8-turn condenser, and put these as close together as possible in the magneticmeridian ... with the needle between the windings. Each single circuit ... gave a deflection of 45° ... When two were connected the deflection was 60°, and when finally all three were put in magnetic operation, the deflection grew to only 70°. It appears clearly from this that the angle of deflection is not in a simple ratio with the magnetic force acting on the needle....

In analyzing the astonishingly increased power which the condenser gives to the magnetic effect of a circuit, the first question that arises is how the effect varies with the number of turns, whether it increases indefinitely or reaches a maximum beyond which additional turns have no effect. The answer to this first question is linked to the solution of another, viz, whether the degrees deflection are a direct expression of the measure of the magnetic force or not.

To instruct myself on this point I made use of three separate circuits, each containing an 8-turn condenser, and put these as close together as possible in the magneticmeridian ... with the needle between the windings. Each single circuit ... gave a deflection of 45° ... When two were connected the deflection was 60°, and when finally all three were put in magnetic operation, the deflection grew to only 70°. It appears clearly from this that the angle of deflection is not in a simple ratio with the magnetic force acting on the needle....

Neither Poggendorf nor Schweigger seems to have ruled out, on logical grounds alone, the possibility of deflections greater than 90°, with the loop-plane in the magnetic meridian, though Poggendorf does add a vague note that if the needle deflected too far it would encounter forces of the opposing sign.

Poggendorf experimented with the size of the circuit wires, finding that larger wires led to greater deflections. He noted that the size of the cell plates and the nature of the cell’s moist conductors would certainly have a great effect, but that to investigate these in detail would take undue time, and he therefore proposed to keep this part of the apparatus constant, using one pair of zinc and copper plates 3.6 inches in diameter, separated by cloth soaked in ammonium-chloride solution.

Poggendorf’s principal quantitative study of his magnetic condenser used 13 identical coils, each with 100 turns. In order that the turns should all be at approximately the same distance from the needle, the coils were wound of the finest brass wire that could be silk-insulated, the wire diameter being 0.02 lines. On adding coils one at a time across the cell (i.e., connecting them in parallel), the deflections were as follows:

Adding some coils with fewer turns, and connecting various combinations “as acontinuum” (i.e., in series), the deflections using the same cell were:

Making a few coils from wire with 1/8-line diameter, the deflections, again using the same cell were:

Since the needle used in these experiments was almost as long as the inside clearance of the coils, no simple tangent law can be applied, and it is not possible to discover an equivalent circuit in modern terms. However, the constancy of the deflections for large numbers of turns in each case indicates that the cell voltage and resistance were fairly constant, and a rough estimate suggests that the cell resistance was comparable to the resistance of one of the 100-turn coils of fine wire. Such a value means that cell resistance limited the maximum deflections for the parallel-connected multipliers, while coil resistance fixed the limit in the series case.

For all of these reasons, it was impossible that any useful functional law could be obtained from the data.

Poggendorf concluded only that “the amplifying power of the condenser does not increase without limit, but has a maximum value dependent on the conditions of plate area and wire size.” He added two other significant comments derived from various observations, that the basic Oersted phenomenon is independent of the earth’s magnetism, and that the phenomenon is localized, i.e., is not affected by distant parts of the circuit.

Only a small fraction of Poggendorf’s paper is devoted to elucidating the properties of the condenser. A similar amount is concerned with refuting various proposals, such as those of Berzelius and Erman, about distributions of magnetic polarity in a conducting wire to account for Oersted’s results. More than half of the paper describes results obtained by using the condenser to compare conductivities and cell polarities under conditions where no effect had previously been detectable. Notable is the observation of needle deflections in circuits whose connecting wires are interrupted by pieces of graphite, manganese dioxide, various sulphur compounds, etc., materials which had previously been considered as insulators in galvanic circuits. Poggendorf gives these the name of “semi-conductor” (halb-Leiter).

Figure 6.Figure 6.—Electromagnetic instruments of James Cumming, used at Cambridge in 1821. One is a single-wire “galvanometer,” following Ampère’s definition. Cumming called the multiple-turn construction “galvanoscopes.” He showed how to increase their sensitivity by partial cancellation of the earth’s magnetism at the location of the compass needle. (FromTransactions of the Cambridge Philosophical Society, vol. 1, 1821.)

Figure 6.—Electromagnetic instruments of James Cumming, used at Cambridge in 1821. One is a single-wire “galvanometer,” following Ampère’s definition. Cumming called the multiple-turn construction “galvanoscopes.” He showed how to increase their sensitivity by partial cancellation of the earth’s magnetism at the location of the compass needle. (FromTransactions of the Cambridge Philosophical Society, vol. 1, 1821.)

Cumming’s first mention of the multiplier phenomenon, in his paper of April 2,1821,[22]is quite casual, and describes only a one-turn construction. He speaks first of single-turn ring of thick, brass wire, and after noting that the sides of a circuit produce additive effects on a needle, he comments that a flattened rectangular loop produces nearly quadruple the effect of a single wire. The paper is primarily a review of Oersted’s work, with references to electromagnetic observations before Oersted, and accounts of various related but nonmultiplier experiments that Cumming has made. His second paper, of May 21st, contains a fine plate (fig. 6) illustrating arrangements used in investigating the subject of the paper’s title “The Application of Magnetism as a Measure of Electricity.” (Neither Poggendorf nor any of his commentators ever illustrated his “condenser.”)

Although this plate is never referred to in the paper itself, a nearby “Description” gives a few comments. The two wire patterns shown are noted as simply “forms of spiral for increasing the electromagnetic intensity.” The mounted wire loop, with enclosed compass needle and terminal mercury cups, is clearly identical in principle with the devices of Schweigger and Poggendorf, and is called a “galvanoscope.” The largest structure illustrated does not involve the multiplying effect. It is called a “galvanometer,” consistent with Ampère’s definition of that word. To use it, two leads of a voltaic circuit are inserted into the mercury cups AC and BD, and the board EFGH carrying the cups is moved vertically until some “standard” deflection is obtained on the compass needle below. The relative “strength” of the circuit is then given by the calibrated position of the sliding section. Uncertainties are undoubtedly introducedby the arbitrary positions of the connecting wires from the test circuit to the mercury cups, but Cumming drew some interesting conclusions from various measurements he made.

Observing needle deflections for various positions of the wire A-B, with a “constant” voltaic circuit, he found that “the tangent of the deviation varies inversely as the distance of the connecting wire from the magnetic needle.” Here is a combination of the deflection law for a needle in a transverse horizontal field and the magnetic-force law for a long, straight wire. The latter had been determined experimentally by Biot and Savart, in November 1820, by timing the oscillations of a suspended magnet.[29]

Figure 7.Figure 7.—“Schweigger multiplier” used by Oersted in 1823. A thin magnetic needle is held in a light, paper sling at F, suspended by a fine, vertical fiber. (FromAnnales de Chimie et de Physique.)

Figure 7.—“Schweigger multiplier” used by Oersted in 1823. A thin magnetic needle is held in a light, paper sling at F, suspended by a fine, vertical fiber. (FromAnnales de Chimie et de Physique.)

Cumming considers his straight-wire calibrated “galvanometer” to be a device for “measuring” galvanic electricity; on the other hand, his multiple-loop “galvanoscopes” are for “discovering” galvanic electricity. With the multiplier instrument, he found galvanic effects (i.e., needle deflections) using copper and zinc electrodes with several acids not previously known to create galvanic action. A potassium-mercury amalgam electrode created a powerful cell with zinc as the positive electrode, establishing both the metallic nature of potassium and the fact that it is the most negative of all metals.

In a third paper, presented April 28, 1823,[30]Cumming reports use of the galvanoscope in experiments on the thermoelectric phenomena recently discovered by Seebeck. His note that “for the more minute effects a compass was employed in the galvanoscope, having its terrestrial magnetism neutralized ...” seems to be the earliest mention of this version of the astatic principle, a technique whose dramatic effects were especially valuable in low-resistancethermoelectriccircuits, where the extra resistance of additional multiplier turns largely offsets their magnetic contribution. In detail, “the needle is neutralized by placing a powerful magnet North and South on a line with its center; and another, which is much weaker, East and West at some distance above it: by means of the first the needle is placed nearly at right angles to the meridian, and the adjustment is completed by the second.”

On varying the length of the connecting wire of the circuit, Cumming found the deflections of the multiplier needle to be in a nearly reciprocal relation. He speaks of the “conducting power of the wire,” and seems not far from visualizing Ohm’s law, of which no published form appeared until 1826. Ohm’s own experiments were made with very similar apparatus.

An effort has been made to show that electrical experimenters prior to Oersted’s discovery in 1820 were in desperate need of some electrical instrument for galvanic or voltaic circuits that would combine sensitivity, simplicity, reliability, and quick response.The nearly simultaneous creation by Schweigger, Poggendorf and Cumming of an arrangement consisting of a coil of wire and a compass needle provided the first primitive version of a device to fill that need.

Figure 8.Figure 8.—Completely useless arrangementof vertical coil and horizontal, unmagnetized needle, presented in theEdinburgh Philosophical Journalof 1821 as “Poggendorf’s Galvano-Magnetic Condenser.” Almost every aspect of Poggendorf’s instrument has been incorrectly represented.

Figure 8.—Completely useless arrangementof vertical coil and horizontal, unmagnetized needle, presented in theEdinburgh Philosophical Journalof 1821 as “Poggendorf’s Galvano-Magnetic Condenser.” Almost every aspect of Poggendorf’s instrument has been incorrectly represented.

It appears that Schweigger is clearly entitled to credit for absolute priority in the discovery, but the original sources suggest that both his understanding of the device and the subsequent researches he performed with it were markedly inferior to those of the other independent discoverers. In using the generic label, “Schweigger’s Multiplier,” there have been historical examples of attributing to Schweigger considerably more sophistication than is justified. Figure 7 shows an instrument designed by Oersted in 1823,[20]which he says “differs in only minor particulars from that of M. Schweigger.” On comparing figure 7 with figures 3, 4, or 5, the remark seems overly generous.

The history of the multiplier instruments has had its fair share of erroneous reports and misleading clues. A fine example is the illustration of figure 8, taken from what is often quoted as the first report in English on Poggendorf’s “Galvano-Magnetic Condenser.”[31]The sketch is the editor’s interpretation of a verbal description given him by a visiting Danish chemist who, in turn, had received the information in a letter from Oersted. It incorporates, faithful to the description, a “spiral wire ... established vertically,” with a needle “in the axis of the spiral,” yet by misunderstanding of the axial relations and of the ratio of length to diameter for the coil, a completely meaninglessarrangementhas resulted. The confusion is compounded by the specifying of anunmagnetizedneedle.

Schweigger and Poggendorf, through their editorial positions, were among the best known of all European scientists for several decades. On one basis or another their reputations are firmly established. Comparison of the accounts of the early “multipliers,” however, suggests that the Reverend James Cumming, professor of chemistry at the University of Cambridge, was a very perceptive philosopher. This was well understood by G. T. Bettany who wrote in theDictionary of National Biographythat Cumming’s early papers “though extremely unpretentious,” were “landmarks in electromagnetism and thermoelectricity,” and concluded that: “Had he been more ambitious and of less uncertain health, his clearness and grasp and his great aptitude for research might have carried him into the front rank of discoverers.”

I wish to thank Dr. Robert P. Multhauf, chairman of the Department of Science and Technology in the Smithsonian Institution’s Museum of History and Technology, for encouragement in the writing of this paper and for the provision of opportunity to consult the appropriate sources. To Dr. W. James King of the American Institute ofPhysics, I am grateful for many provocative discussions on this and related topics.

FOOTNOTES:[1]A. Volta, “On the Electricity Excited by the Mere Contact of Conducting Substances of Different Kinds,”Philosophical Transactions of the Royal Society of London(1800), vol. 90, pp. 403-431.[2]Some little-known but delightful observations in the prehistory of electromagnetism are described in a letter written byG. W. Schillingfrom London to the Berlin Academy on July 8, 1769, published as “Sur les phénomènes de l’Anguleil Tremblante” [Nouveaux Mémoires de l’Académie Royale des Sciences et Belles-Lettres, 1770 (Berlin, 1772), pp. 68-74], translated to French from the original German. The letter recounts a multitude of experiments with various electric eels. The two observations of electromagnetic interest are that a piece of iron held by the hand in the eel’s tank could be felt quivering even when the fish was stationary several inches away, and a compass needle showed a deflection, both in the water near the fish, and outside the tank, also with the fish stationary.[3]Abraham Bennet,Philosophical Transactions of the Royal Society of London(1787), p. 26.[4]Op. cit. (footnote 1), p. 403.[5]Philosophical Magazine(1800), vol. 7, pp. 289-311. [For a facsimile reprint, seeGalvani-Volta(Bern Dibner’s Burndy Library Publication No. 7), Norwalk, Connecticut, 1952.][6]Michael Faraday,Experimental Researches in Electricity, vol. 1 (London, 1839), paragraph 739, dated January 1834.[7]Ibid., sec. 741.[8]James Cumming, “On the Application of Magnetism as a Measure of Electricity,”Transactions of the Cambridge Philosophical Society(1821), vol. 1, pp. 282-286. [Also published inPhilosophical Magazine(1822), vol. 60, pp. 253-257.][9]H. C. Oersted,Experimenta Circa Effectum Conflictus Electrici in Acum Magneticam(Copenhagen, July 21, 1820).[10]Full details of Oersted’s work and publications are inOersted and the Discovery of Electromagnetism(Bern Dibner’s Burndy Library Publication No. 18), Norwalk, Connecticut, 1961. The original Latin version and first English translation are reproduced inIsis(1928), vol. 34, pp. 435-444.[11]A. M. Ampère,Annales de Chimie et de Physique(1820), vol. 15, p. 67. The word “galvanometer” had been used much earlier byBischof, “On Galvanism and its Medical Applications,”The Medical and Physical Journal(1802), vol 7, p. 529, for a form of goldleaf electroscope shown here in figure 2, but this use of the word does not seem to have been adopted by others.[12]Op. cit. (footnote 6), paragraph 283, dated January 1833. A similar attitude was expressed in the same year byChristie,Philosophical Transactions of the Royal Society of London(1833), vol. 123, p. 96: “I adopt the word current as a convenient mode of expression, ... but I would not be considered as adopting any theoretical views on the subject....”[13]Some prominent examples of this brevity of treatment are inE. Hoppe,Geschichte derElektrizität(Leipzig, 1884);O. Mahr,Geschichtliche Einzeldarstellungen aus der Elektrotechnik(Berlin, 1941);R. S. Whipple, “The Evolution of the Galvonometer,”Journal of Scientific Instruments(1934), vol. 7, pp. 37-43;William Sturgeon,Scientific Researches(Bury, 1850);A. W. Humphreys, “The Development of the Conception and Measurement of Electric Current,”Annals of Science(1937), vol. 2, pp. 164-178.[14]M. Speter, “Klärung der Multiplikator-Prioritätsfrage Schweigger-Poggendorf,”Zeitschrift für Instrumentenkunde(1937) vol. 57, pp. 29-32.[15]T. Seebeck, “Über den Magnetismus der Galvanischen Kette,”Abhandlungen der Koenigliche Akademie der Wissenschaften zu Berlin(1820-1821), pp. 289-346. The phrase “Schweigger’s multiplier” is used on page 319. The many experiments described in this paper added little or nothing to contemporary appreciation of the multiplier as an instrument.[16]J. S. C. Schweigger,Journal für ChemieundPhysik(1821), vol. 31, pp. 1-18, 35-42. Pages 1-6 are the paper presented in Halle on September 16, 1820; pages 7-18 are the paper presented in Halle on November 4, 1820, and pages 35-42 are “a few additional words.” The preface to the whole volume is dated January 1, 1821. A somewhat earlier public announcement referring to Schweigger’s discovery appeared in theAllgemeine Literatur-Zeitung(November 1820), no. 296, cols. 622-624, but this was lacking in detail and seems not to have been noticed by any scientists.[17]P. Erman,Umrisse zu den physischen Verhältnissen des von Herrn Prof. Oersted entdeckten elektro-chemischen Magnetismus(Berlin, 1821). Hoppe (footnote 13) states that Erman’s book was published in May; however, it is referred to in a letter dated April 3, 1821, byRaschig,Annalen der Physik(1821), vol. 67, pp. 427-436.[18]Op. cit. (footnote 16), vol. 32, pp. 38-50.[19]Annalen der Physik(1821), vol. 67, pp. 382-426, and footnote on pages 429-430 of same volume. The footnote accompanies the article by Raschig mentioned in footnote 17.[20]H. C. Oersted, “Sur leMultiplierelectro-magnetique de M. Schweigger, et sur quelques applications qu’on en a faites,”Annales de Chimie et de Physique(1823), vol. 22, pp. 358-365.[21]“Versuche mit dem electrisch-magnetischen Multiplicator,”Annalen der Physik(1821), vol. 67, pp. 427-436.[22]Transactions of the Cambridge Philosophical Society(1821), vol. 1, pp. 269-278.[23]Op. cit. (footnote 8).[24]The GermanwordKettehas been translated as “circuit” throughout. Although the equivalence of these words is clear, for example, in Ohm’s work of 1826, the context in whichKetteis sometimes used in 1820 and 1821 indicates that the concept of a “circuit,” in the sense of the wiring external to the source of electricity, has not been established. The wiring is regarded more as something incidental, used to “close” the cell, the cell being considered essentially the whole of the apparatus. This view underlies the many attempts to correlate the Oersted phenomena with cell materials and design, and with the use of such terms as “chemical magnetism” by Erman and others.[25]The reference here is to the Oersted-type experiments described in two papers by authors other than Schweigger on pages 19 to 34 of the volume.[26]Op. cit. (footnote 19), pp. 422-426.[27]One “line” seems to have been about 1/12 inch.[28]J. G. Poggendorf, “Physisch-chemische Untersuchungen zur näheren Kenntniss des Magnetismus der voltaischen Säule,”Isis von Oken(1821), vol. 8, pp. 687-710. Most of Poggendorf’s numerical data is also inC. H. Pfaff,Der Elektromagnetismus(Hamburg, 1824), along with some of Pfaff’s own work.[29]Reported inAnnales de Chimie et de Physique(1820), vol. 15, pp. 222-223.[30]“On the Development of Electro-Magnetism by Heat,”Transactions of the Cambridge Philosophical Society(1823), vol. 2, pp. 47-76.[31]“Account of the New Galvano-Magnetic Condenser invented by M. Poggendorf of Berlin,”Edinburgh Philosophical Journal(July 1821), vol. 5, pp. 112-113.

[1]A. Volta, “On the Electricity Excited by the Mere Contact of Conducting Substances of Different Kinds,”Philosophical Transactions of the Royal Society of London(1800), vol. 90, pp. 403-431.

[2]Some little-known but delightful observations in the prehistory of electromagnetism are described in a letter written byG. W. Schillingfrom London to the Berlin Academy on July 8, 1769, published as “Sur les phénomènes de l’Anguleil Tremblante” [Nouveaux Mémoires de l’Académie Royale des Sciences et Belles-Lettres, 1770 (Berlin, 1772), pp. 68-74], translated to French from the original German. The letter recounts a multitude of experiments with various electric eels. The two observations of electromagnetic interest are that a piece of iron held by the hand in the eel’s tank could be felt quivering even when the fish was stationary several inches away, and a compass needle showed a deflection, both in the water near the fish, and outside the tank, also with the fish stationary.

[3]Abraham Bennet,Philosophical Transactions of the Royal Society of London(1787), p. 26.

[4]Op. cit. (footnote 1), p. 403.

[5]Philosophical Magazine(1800), vol. 7, pp. 289-311. [For a facsimile reprint, seeGalvani-Volta(Bern Dibner’s Burndy Library Publication No. 7), Norwalk, Connecticut, 1952.]

[6]Michael Faraday,Experimental Researches in Electricity, vol. 1 (London, 1839), paragraph 739, dated January 1834.

[7]Ibid., sec. 741.

[8]James Cumming, “On the Application of Magnetism as a Measure of Electricity,”Transactions of the Cambridge Philosophical Society(1821), vol. 1, pp. 282-286. [Also published inPhilosophical Magazine(1822), vol. 60, pp. 253-257.]

[9]H. C. Oersted,Experimenta Circa Effectum Conflictus Electrici in Acum Magneticam(Copenhagen, July 21, 1820).

[10]Full details of Oersted’s work and publications are inOersted and the Discovery of Electromagnetism(Bern Dibner’s Burndy Library Publication No. 18), Norwalk, Connecticut, 1961. The original Latin version and first English translation are reproduced inIsis(1928), vol. 34, pp. 435-444.

[11]A. M. Ampère,Annales de Chimie et de Physique(1820), vol. 15, p. 67. The word “galvanometer” had been used much earlier byBischof, “On Galvanism and its Medical Applications,”The Medical and Physical Journal(1802), vol 7, p. 529, for a form of goldleaf electroscope shown here in figure 2, but this use of the word does not seem to have been adopted by others.

[12]Op. cit. (footnote 6), paragraph 283, dated January 1833. A similar attitude was expressed in the same year byChristie,Philosophical Transactions of the Royal Society of London(1833), vol. 123, p. 96: “I adopt the word current as a convenient mode of expression, ... but I would not be considered as adopting any theoretical views on the subject....”

[13]Some prominent examples of this brevity of treatment are inE. Hoppe,Geschichte derElektrizität(Leipzig, 1884);O. Mahr,Geschichtliche Einzeldarstellungen aus der Elektrotechnik(Berlin, 1941);R. S. Whipple, “The Evolution of the Galvonometer,”Journal of Scientific Instruments(1934), vol. 7, pp. 37-43;William Sturgeon,Scientific Researches(Bury, 1850);A. W. Humphreys, “The Development of the Conception and Measurement of Electric Current,”Annals of Science(1937), vol. 2, pp. 164-178.

[14]M. Speter, “Klärung der Multiplikator-Prioritätsfrage Schweigger-Poggendorf,”Zeitschrift für Instrumentenkunde(1937) vol. 57, pp. 29-32.

[15]T. Seebeck, “Über den Magnetismus der Galvanischen Kette,”Abhandlungen der Koenigliche Akademie der Wissenschaften zu Berlin(1820-1821), pp. 289-346. The phrase “Schweigger’s multiplier” is used on page 319. The many experiments described in this paper added little or nothing to contemporary appreciation of the multiplier as an instrument.

[16]J. S. C. Schweigger,Journal für ChemieundPhysik(1821), vol. 31, pp. 1-18, 35-42. Pages 1-6 are the paper presented in Halle on September 16, 1820; pages 7-18 are the paper presented in Halle on November 4, 1820, and pages 35-42 are “a few additional words.” The preface to the whole volume is dated January 1, 1821. A somewhat earlier public announcement referring to Schweigger’s discovery appeared in theAllgemeine Literatur-Zeitung(November 1820), no. 296, cols. 622-624, but this was lacking in detail and seems not to have been noticed by any scientists.

[17]P. Erman,Umrisse zu den physischen Verhältnissen des von Herrn Prof. Oersted entdeckten elektro-chemischen Magnetismus(Berlin, 1821). Hoppe (footnote 13) states that Erman’s book was published in May; however, it is referred to in a letter dated April 3, 1821, byRaschig,Annalen der Physik(1821), vol. 67, pp. 427-436.

[18]Op. cit. (footnote 16), vol. 32, pp. 38-50.

[19]Annalen der Physik(1821), vol. 67, pp. 382-426, and footnote on pages 429-430 of same volume. The footnote accompanies the article by Raschig mentioned in footnote 17.

[20]H. C. Oersted, “Sur leMultiplierelectro-magnetique de M. Schweigger, et sur quelques applications qu’on en a faites,”Annales de Chimie et de Physique(1823), vol. 22, pp. 358-365.

[21]“Versuche mit dem electrisch-magnetischen Multiplicator,”Annalen der Physik(1821), vol. 67, pp. 427-436.

[22]Transactions of the Cambridge Philosophical Society(1821), vol. 1, pp. 269-278.

[23]Op. cit. (footnote 8).

[24]The GermanwordKettehas been translated as “circuit” throughout. Although the equivalence of these words is clear, for example, in Ohm’s work of 1826, the context in whichKetteis sometimes used in 1820 and 1821 indicates that the concept of a “circuit,” in the sense of the wiring external to the source of electricity, has not been established. The wiring is regarded more as something incidental, used to “close” the cell, the cell being considered essentially the whole of the apparatus. This view underlies the many attempts to correlate the Oersted phenomena with cell materials and design, and with the use of such terms as “chemical magnetism” by Erman and others.

[25]The reference here is to the Oersted-type experiments described in two papers by authors other than Schweigger on pages 19 to 34 of the volume.

[26]Op. cit. (footnote 19), pp. 422-426.

[27]One “line” seems to have been about 1/12 inch.

[28]J. G. Poggendorf, “Physisch-chemische Untersuchungen zur näheren Kenntniss des Magnetismus der voltaischen Säule,”Isis von Oken(1821), vol. 8, pp. 687-710. Most of Poggendorf’s numerical data is also inC. H. Pfaff,Der Elektromagnetismus(Hamburg, 1824), along with some of Pfaff’s own work.

[29]Reported inAnnales de Chimie et de Physique(1820), vol. 15, pp. 222-223.

[30]“On the Development of Electro-Magnetism by Heat,”Transactions of the Cambridge Philosophical Society(1823), vol. 2, pp. 47-76.

[31]“Account of the New Galvano-Magnetic Condenser invented by M. Poggendorf of Berlin,”Edinburgh Philosophical Journal(July 1821), vol. 5, pp. 112-113.

U.S. GOVERNMENT PRINTING OFFICE: 1964

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402—Price 20 cents

Aldini, Giovanni,124

Ampère, André Marie,127,129

Arago, Dominique François Jean,129

Bennet, Abraham,124

Berzelius, Jöns Jakob,133

Bettany, G. T.,136

Biot, Jean Baptiste,135

Carlisle, Anthony,124

Cavallo, Tiberio,124

Cavendish, Henry,123

Cummings, James,125,127,133

Erman, Paul,128,129,132,133

Faraday, Michael,125

Galvani, Luigi,124

Gay-Lussac, Joseph Louis,125

Gilbert, L. W.,127,132

Meineke, ——,128

Nicholson, William,124

Oersted, Hans Christian,125,132

Ohm, Georg Simon,123,135

Oken, Lorenz,132

Pfaff, Christian Heinrich,132

Poggendorf, Johann Christian,127,132,136

Raschig, Christoph Eusebius,129

Ritter, Johann Wilhelm,129

Savart, Felix,135

Schweigger, Johann Salomo Christoph,127,132,136

Seebeck, T.,128,135

Soemmering, S. T.,125

Speter, M.,127,128

Thenard, Louis Jacques,125

Tromsdorff, Johann Bartholomacus,125

Van Marum, Martin,123

Volta, Alessandro,123,124,127

Wollaston, W. H.,125

Zamboni, Giuseppe,132

Transcriber’s Corrections:Obvious typographical errors have been corrected as follows:Page127: “in the magnetic meridian, then”—had “meridan.”Page128: “mainly of the postscript, with”—had “postcript.”Page134: “paper of April 2, 1821,[22] is quite”—had “1921.”Page135: “thermoelectric circuits, where”—had “thermoelectirc.”Page135: “arrangement has resulted.”—had “arragnement.”Page135: “King of the American Institute of Physics.”—had “Physic.”Footnote13: “Geschichte der Elektrizität”—had “Elektrizitat.”Footnote16: “Journal für Chemie und Physik”—had “and.”Footnote24: “The German wordKette”—had “work.”Questionable spellings have been retained as follows:Page125andIndex: J. B. [Johann Bartholomacus] Tromsdorff—should be Johann Bartholomäus Trommsdorff?Page129: “sulphur, phosphorous and carbon”—should be “phosphorus” but may be misspelled in the quoted material?Footnote20: “Sur le Multiplier electro-magnetique”—should be “Multiplicateur”?

Obvious typographical errors have been corrected as follows:

Page127: “in the magnetic meridian, then”—had “meridan.”

Page128: “mainly of the postscript, with”—had “postcript.”

Page134: “paper of April 2, 1821,[22] is quite”—had “1921.”

Page135: “thermoelectric circuits, where”—had “thermoelectirc.”

Page135: “arrangement has resulted.”—had “arragnement.”

Page135: “King of the American Institute of Physics.”—had “Physic.”

Footnote13: “Geschichte der Elektrizität”—had “Elektrizitat.”

Footnote16: “Journal für Chemie und Physik”—had “and.”

Footnote24: “The German wordKette”—had “work.”

Questionable spellings have been retained as follows:

Page125andIndex: J. B. [Johann Bartholomacus] Tromsdorff—should be Johann Bartholomäus Trommsdorff?

Page129: “sulphur, phosphorous and carbon”—should be “phosphorus” but may be misspelled in the quoted material?

Footnote20: “Sur le Multiplier electro-magnetique”—should be “Multiplicateur”?

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