Nineteenth-Century Developments in Coiled Instruments and Experiences with Electromagnetic Induction

Summary

Faraday demonstrated electromagnetic induction in 1831 using an iron ring wound with two wire coils; on interrupting battery current in one coil, momentary currents arose in the other. Between Faraday's ring and the induction coil, coiled instruments developed via meandering paths. This paper explores the opening phase of that work in the late 1830s, as the iron core, primary wire coil, and secondary wire coil were researched and differentiated. ‘Working knowledge’ (defined by Baird) gained with materials and phenomena was crucial to innovations. To understand these material-based interactions, I experimented with hand-wound coils, along with examining historical texts, drawings, and artefacts. My experience recovered the historical dead-end of two-wire coils and ensuing work with long-coiled single conductors initiated by Faraday and Henry. The shock and spark heightened in these coils provided feedback to the many instrumental configurations tested by Page, Callan, Sturgeon, Bachhoffner, and others. The continuous conductor differentiated into two segments soldered together: a thick short wire carrying battery current and a long thin wire for elevating shocks (voltage). The joined wires eventually separated, yet their transitional connection documents belief that the induced effects depend on continuity. These coiled instruments, with their intertwined histories, show experimental work and understandings in the process of developing. Seeing the nonlinear paths by which these instruments developed deepens our understanding of historical experiences, and of how people learn.

My thoughts about many aspects of this work were extended through discussions with Ronald Anderson, Davis Baird, Constance Barsky, Paolo Brenni, Stephan Epstein, Peter Heering, Richard Kremer, Frank James, Ben Marsden, Alberto Martinez, Arthur Molella, Philip Morrison, Giuliano Pancaldi, David Pantalony, Roger Sherman, George Smith, Friedrich Steinle, Klaus Staubermann, Ryan Tweney, and Yaakov Zik. The manuscript benefited from thoughtful readings by Alain Bernard, David Pantalony, and the reviewers. James Day, Thomas Greenslade, Ellen Kuffeld, Thierry Lalande, Francis Manasek, Roger Sherman, and Adrian Whicher offered helpful insights from instruments in their collections. This historical study responds to teaching shared with Fiona McDonnell, Petra Lucht, Lisa Schneier, Bonnie Tai, and Eleanor Duckworth's Piaget-inspired understandings of development. Thomas Cavicchi responded to my electrical questions; Robert Post encouraged and deepened my study of Page. The Dibner Institute for the History of Science and Technology provided support that made this research possible. For lab space, electronic instruments, and discussions of experiments, I thank Wolfgang Rueckner and Joseph Peidle of the Harvard University Science Center; James Bales, Ed Moriarty, and Anthony Caloggero of the Edgerton Center at MIT; Markos Hankin and Bill Sanford of MIT Physics Demonstrations. Alva Couch sustains my daily developments. I give this study to the memory of the experimental and diverse research and teaching of Philip and Phylis Morrison and James Schmolze.

Notes

¹Faraday's original iron ring is preserved at the Royal Institution, London, number RI AC 20. The battery used was a series of ten pairs of copper and zinc plates. It connected to wire made up of three 24-foot lengths that were wrapped in cloth and string and coiled about one side of the iron ring (figure 1). Around the ring's other side were two wire lengths (totalling 60 feet) that connected to a galvanometer or other means of detecting electricity (Michael Faraday, entry of 29, August 1831 in Faraday's Diary: Being the Various Philosophical Notes of Experimental Investigation, Thomas Martin, ed., 1 (London, 1932), and ‘On the Induction of Electric Currents’, First Series, read 24 November, 1831, Experimental Researches in Electricity (abbreviated ERE), vol. 1 (Sante Fe NM, 2000, reprinted from 1839), ¶27–32.

²Immediately preceding his discovery of electromagnetic induction, Faraday explored transient phenomena in acoustics and vibrations ‘On a Peculiar Class of Acoustical Figures; and on Certain Forms Assumed by Groups of Particles Upon Vibrating Elastic Surfaces’, 1831, 314–32 in Experimental Researches in Chemistry and Physics (London, 1991); ‘On the Forms and States Assumed by Fluids in Contact with Vibrating Elastic Surfaces’, 1831, 335–58 in the same volume. The relation of these studies to his subsequent work is discussed in Ryan Tweney, ‘Stopping Time: Faraday and the Scientific Creation of Perceptual Order’, Physis 29 (1992) 149–64; Elizabeth Cavicchi, ‘Faraday and Piaget: Experimenting in Relation with the World’, Perspectives on Physics, 14 (2006), 66–96.

³See ¶15 42, 83, 91, 157 in the Diary (note 1) for Faraday's unsuccessful attempts (including one on the first day of his discovery) to observe an induced spark.

⁴Faraday 1831, ERE (note 1), v. 1, ¶6,34–38.

⁵The full title of Sturgeon's self-edited journal is The Annals of Electricity, Magnetism, Chemistry, and Guardian of Experimental Science. For a discussion of Sturgeon's life, experiments, and times, see Iwan Morus, Frankenstein's Children: Electricity, Exhibition, and Experiment in Early-Nineteenth-Century London (Princeton, 1998).

⁶The Royal Institute and the Adelaide Gallery are described and contrasted in Morus (note 4), which also excerpts contemporary remarks on Bachhoffner's science lecturing, and also in J. A. Fleming, The Alternate Current Transformer in Theory and Practice, 2 (London, 1892), 1.

⁷E. M. Clarke mentioned getting Dr Faraday's opinion on his invention in ‘Description of E. M. Clarke's Electrepeter’, Annals of Electricity, 1 (1837) 66. His workshop, then at 9, Agar St., West Strand, subsequently moved opposite the Adelaide Gallery, Gloria Clifton, Directory of British Scientific Instrument Makers 1550–1851 (London, 1995), 57. Clarke, his Irish origins and association with Nicolas Callan are discussed in J. E. Burnett and A. D. Morrison-Low, Vulgar & Mechanick: The Scientific Instrument Trade in Ireland, 1650–1921 (Dublin, 1989); Charles Mollan and John Upton, The Scientific Apparatus of Nicholas Callan and other Historical Instruments (Maynooth, 1994).

⁸For Callan's biography and background, see P. J. McLaughlin, Nicholas Callan: Priest-Scientist 1799–1864 (Dublin, 1964); Niels Heathcote, ‘Essay Review: N. J. Callan Inventor of the Induction Coil’, Annals of Science, 21 (1965), 145–67; for his instruments, see Charles Mollan and John Upton, The Scientific Apparatus of Nicholas Callan and other Historic Instruments (Maynooth Ireland, 1994). Many of Callan's original instruments are on display at the Museum of Ecclesiology, Maynooth College, Ireland.

⁹Albert E. Moyer, Joseph Henry: The Rise of an American Scientist (Washington, DC, 1997).

¹⁰Robert Post, Physics, Patents & Politics: A Biography of Charles Grafton Page (New York, 1976).

¹¹For the association between Page and Davis, see Roger Sherman, ‘Charles Page, Daniel Davis, and their electromagnetic apparatus’, Rittenhouse, 2 (2) (1988), 34–47. Dr William King, electrician, is listed at 54 Cornhill St. in the Boston City Directory, Stimpson & Claff, from 1832–1838; in 1831, he was listed at 4 Schollay's buildings. In 1837, his former assistant Daniel Davis Jr set up a philosophical instrument-making shop at 11 Cornhill; Timothy Claxton and Joseph Wightman started theirs at 33 Cornhill in the following year. In 1840, the year after King's death, another of his assistants, William A. Orcutt, established himself as an electrician at 30 Cornhill St.

¹²Many attributed the 1858 cable's transmission failure to Wildeman Whitehouse's use of high tension from enormous induction coils to overcome the long cable's resistance. Report of the Joint Committee Appointed by the Lords … and the Atlantic Telegraph Company to Inquire into the construction of Submarine Telegraph Cables (London 1861).

¹³N. J. Callan, ‘On the Induction Apparatus’, Philosophical Magazine, 14 (1857), 323–40.

¹⁴(Charles Grafton Page), The American Claim to the Induction Coil and its electrostatic developments (Washington, DC, 1867); Robert C. Post, ‘Stray Sparks from the Induction Coil: The Volta Prize and the Page Patent’, Proceedings of the IEEE, 64 (1976), 1279–86.

¹⁵Théodose DuMoncel described Page's book as ‘un long panégyrique dans lequel il attribue tout à l'Amérique et à lui en particulier’; Exposé des Applications de L’Électricité, 2 (Paris, 1873), 243.

¹⁶Fleming (note 6).

¹⁷J. A. Fleming, Memories of a Scientific Life (London, 1934), 133.

¹⁸Fleming (note 5), 2, 1.

¹⁹Willem D. Hackmann collected references on improvements to the induction coil and placed these in reference to surviving artifacts in the collection of the Museum of History of Science at Oxford, ‘The Induction Coil in Medicine and Physics: 1835–1877’, in Studies in the History of Scientific Instruments, edited by C. Blondel, F. Parot, A. Turner, M. Williams (London, 1989), 235–50, quote 236.

²⁰Davis Baird, Thing Knowledge: A Philosophy of Scientific Instruments (Berkeley, 2004), chapter 3.

²¹The quote from Richard Feynman, on p. 114 of Baird (note 20) is taken from J. Gleick, Genius: The Life and Science of Richard Feynman (New York, 1993).

²²David Oldroyd, ‘Non-Written Sources in the Study of the History of Geology: Pros, and Cons, in the Light of the Views of Collingwood and Foucault’, Annals of Science, 56 (1999), 395–415.

²³Oldroyd (note 22), quotes 415, 395.

²⁴Ryan Tweney, ‘Discovering Discovery: How Faraday Found the First Metallic Colloid’, Perspectives on Science, 14 (2006), 97–121; Elizabeth Cavicchi, ‘Experiences with the magnetism of conducting loops: Historical instruments, experimental replications, and productive confusions’, American Journal of Physics 71 (2003), 156–67; David Gooding, Experiment and the Making of Meaning: Human Agency in Scientific Observation and Experiment (Dordrecht, 1990).

²⁵H. O. Sibum, ‘Reworking the Mechanical Value of Heat: Instruments of Precision and Gestures of Accuracy in Early Victorian England’, Studies in the History and Philosophy of Science, 26 (1995), 73–106; Peter Heering, ‘The replication of the torsion balance experiment: the refutation of early nineteenth century German physicists’, in Restaging Coulomb: Usages, Controverses et Réplications autour de la Balance de Torsion, edited by C. Blondel and M. Dörres (Florence, 1994), 47–66.

²⁶Klaus Staubermann, ‘Controlling Vision: The Photometry of Karl Friedrich Zöllner’, Dissertation, Darwin College, Cambridge, UK, 1998.

²⁷Joseph Henry's single-conductor spirals are hailed as ‘chiefs of the clan and true ancestors of our modern coil’ in Fleming (note 6) 2, 1.

²⁸For a fuller discussion of my efforts with the iron ring, see my dissertation, ‘Experimenting with Wires, Batteries, Bulbs and the Induction Coil: Narratives of Teaching and Learning Physics in the Electrical Investigations of Laura, David, Jamie, Myself and the Nineteenth Century Experimenters—Our Developments and Instruments’ (Harvard University, 1999), Chapter 19.

²⁹Faraday, Diary (note 1).

³⁰In the special case of electromagnetic induction between a primary circuit 1 and secondary 2, Faraday's Law can be expressed as: e₂₁ = –M ₂₁(dI ₁ / dt), where ε₂₁ is the electromotive force (V) induced in circuit 2 by circuit 1, M ₂₁ is the mutual inductance between the two circuits, and dI ₁ / dt is the change in current (A) in circuit 1. The mutual inductance depends on such features as the number of loops in the two circuits, their geometries, and the magnetic permeability of the surroundings. See J. D. Jackson, Classical Electrodynamics (New York, 1975), Edward Purcell, Electricity and Magnetism (New York, 1965).

³¹My ring's final windings had a total of 3690 turns of wire. Of these, 400 turns on the primary, and 2164 on the secondary, were usable; Cavicchi (note 28), chapter 19.

³³Cavicchi (note 28), chapter 19.

³²Faraday's low-resistance sources delivered high currents into his low-resistance windings. The resistance of my sources and windings were unmatched, and currents were typically low.

³⁴The rate of change in current within a wire is involved in inducing voltage in that same wire or in separate wires (note 30). When a circuit is closed, on ‘make’, current starts gradually. When the switch opens, at ‘break’, the current stops abruptly. Its more sudden change induces a higher voltage.

³⁵Faraday discussed these cases in ‘On the Magneto-electric Spark and Sock, and on a Peculiar Condition of Electric and Magneto-electric Induction’, Philosophical Magazine, 5 (1834), 349–354.

³⁶Joseph Henry, ‘On the Production of Currents and Sparks of Electricity from Magnetism’, American Journal of Science 22 (1832), 403–408; reprinted in The Scientific Writings of Joseph Henry, 1 (Washington, DC, 1886). No mention of sparking at make appears in Henry's later study, ‘Contributions to Electricity and Magnetism, No. II, “On the Influence of a Spiral Conductor in increasing the Intensity of Electricity from a Galvanic Arrangement of a Single Pair” (read 6 February 1835), American Philosophical Society Transactions (1837), 223–31.

³⁷Faraday, 1834 (note 35) 351. ‘Quantity’ refers to the property we associate with high current at low voltage; ‘intensity’ to high voltage with low current.

³⁸ Faraday contrasted conductor configurations in ‘On the influence by induction of an Electric Current on itself  …  , Ninth Series’, read 20 January 1835, in ERE 1839/2000 (note 1); he also showed that this new induced effect had a different direction from that of the battery current. Henry's efforts are detailed in his paper of 1837 (note 36). His preliminary results were published earlier, ‘Facts in reference to the Spark, &c. from a long conductor uniting the poles of a Galvanic Battery’, Journal of the Franklin Institute (1835) 169–70, and American Journal of Science , 28 (1835) 327–29, Appendix to the above, 329–31. Telegraph engineer W.T. Henley cited Faraday's experiment contrasting sparks from a coiled wire, with those from a straight one in his testimony on the failure of the 1858 Atlantic Telegraph, in the Report (note 11),¶ 2432, 109.

³⁹There was a lesser effect in the same conductor, on starting the battery current.

⁴⁰Gooding (note 24), 159.

⁴¹C. G. Page, ‘Method of increasing shocks, and experiments, with Prof. Henry's apparatus for obtaining sparks and shocks from the Calorimotor’, American Journal of Science 31 (January 1837), 137–41.

⁴²Page (note 41), 141; Page, ‘Medical Application of Galvanism’, Boston Medical and Surgical Journal, June 22, 1836, 333.

⁴³Page's observation, that shock increases as it is taken across more non-current bearing winds, is problematic to reproduce. See Elizabeth Cavicchi, ‘Opening the Circuit to the Body, more Options, and Ambiguity: Charles Grafton Page's Experiment with a Spiral Conductor’, Technology and Culture, in preparation 2006;‘Sparks, Shocks and Voltage Traces as Windows into Experience: The Spiraled Conductor and Star Wheel Interrupter of Charles Grafton Page’, Archives des Sciences, in preparation 2006.

⁴⁴Page (note 41), 139.

⁴⁵Page 1867 (note 14), 3.

⁴⁶Sturgeon's encounter with ‘a Mr. Peaboddy, a scientific American gentleman whom I accidentally met with in the Adelaide Gallery of Practical Science’ is described on p. 67 in William Sturgeon, ‘On the Electric Shock from a single Pair of Voltaic Plates, by Professor Henry, of Yale College, Unites States: Repeated, and new Experiments’ (28 September 1836), Annals of Electricity, 1 (1837), 67–75, reprinted in William Sturgeon, Scientific Researches, Experimental and Theoretical in Electricity, Magnetism, Galvanism, Electro-Magnetism and Electrochemistry (Bury 1850), 282–89. It is critiqued in (Charles Grafton Page) (note 14), footnote p. 11. Francis Peabody (1801–1867) established White Lead manufactories in Salem in 1826 and 1832; Joseph Felt, Annals of Salem, II (Salem 1849). Interested in science, particularly photography, Peabody contributed financially and personally to the Harvard College Observatory and other related projects. Harvard University Archives.

⁴⁷Sturgeon 1837 (note 46), 67.

⁴⁸Sturgeon (note 46), 69.

⁴⁹Sturgeon (note 46), 69.

⁵⁰Sturgeon (note 46), 70.

⁵¹Sturgeon (note 46), 75.

⁵²Sturgeon, ‘On the production of Electric Shocks from a single Voltaic pair’, Annals of Electricity, 1 (1837), 159–60. In Sturgeon's 1850 reprint volume containing many of his papers, he commented that his neglect of contemporary literature allowed him to duplicate Faraday's results. This was ‘no little mortification, because of an apparent plagiary, which I most abominably detested’; Sturgeon 1850 (note 46) p. 45. On the preceding page of the Annals publication, contributor Charles Barker cited Faraday's Ninth Series (reproduced on pages 160–62 and 169–86 of Annals of Electricity, 1 (1837)), and perhaps this tip led Sturgeon to Faraday's work. Morus (note 5), 61–67 treats Sturgeon's work with self-induction phenomena only from Sturgeon's stance, and does not identify the transmission error by which Sturgeon attributed Page's spiral to Joseph Henry.

⁵³Sturgeon, ‘Explanation of the Phenomena, &c.’ Annals of Electricity, 1 (1837), 294–95.

⁵⁴For example, ‘contrary to expectation’, Page experienced shocks from parts of his spiral that were entirely outside the direct current's path (note 41), 139.

⁵⁵Neil Ribe and Friedrich Steinle, ‘Exploratory Experimentation: Goethe, Land and Color Theory’, Physics Today, July 2002, 43–49; Friedrich Steinle, ‘Entering New Fields: Exploratory Uses of Experimentation’, Philosophy of Science 64 (1996), S65–S74; Richard Burian, ‘Exploratory Experimentation and the Role of Histochemical Techniques in the Work of Jean Brachet, 1938–1952’, History and Philosophy of the Life Sciences, 19 (1997), 27–45.

⁵⁶Gooding (note 24), 122–23.

⁵⁷Excerpt from my lab notebook (14 May 1997) in my dissertation (note 28), Chapter 19.

⁵⁸Sturgeon (note 46), 72.

⁵⁹Sturgeon (note 46), 72.

⁶⁰Quote from Faraday (note 38), ¶1110, 340.

⁶¹William Sturgeon, ‘Remarks on the Preceding Paper, with Experiments’, Annals of Electricity, 1 (1837), 186–91, quote 186.

⁶²William Sturgeon, ‘An Experimental Investigation of the Laws Which Govern the Production of Electric Shocks &C, from a Single Voltaic Pair of Metals’, Annals of Electricity, 1 (1837), 192–98, quote 195; reprinted in Sturgeon 1850 (note 46) 289–97. Instrument maker E. M. Clarke also remarked that with magneto-electric machines, long thin wire coils give higher-intensity electricity, ‘Account of Experiments with … Magneto-Electric Machines’, Annals of Electricity, 1 (1837), 73–76.

⁶³Sturgeon (note 62), 197.

⁶⁴Sturgeon, ‘Theoretical Views of the Preceding Phenomena, Secondary Electric Currents, &c.’, Annals of Electricity, 1 (1837), 198–200, quote p. 200; reprinted in Sturgeon 1850 (note 46), 310–311.

⁶⁵Sturgeon, ‘On the theory of Magnetic Electricity’, Annals of Electricity, 1 (1837), 251–58, quote p. 252.

⁶⁶David Gooding, ‘'Magnetic Curves’ and the Magnetic Field: Experimentation and Representation in the History of a Theory’, in The Uses of Experiment: Studies in the Natural Sciences, eds., D. Gooding, T. Pinch, S. Schaffer (Cambridge, UK, 1989), 182–223; ‘Experiment and concept formation in electromagnetic science and technology in England in the 1820s’, History and Technology, 2 (1985), 151–76. An eighteenth-century discussion of ‘magnetic curves’, and an illustration of the iron filings lines around permanent magnets, appears in George Adams, An Essay on Electricity, Explaining the Theory and Practice … with an Essay on Magnetism (London, 1787), 433.

⁶⁷Sturgeon, ‘Application of the Preceding Theory … to the explication of Phenomena’, Annals of Electricity, 1 (1837), 266–277, quote p. 269; reprinted in Sturgeon 1850 (note 46), 310–21. Faraday, Bakerian Lecture, Second Series, 1832, ERE 1839/2000 (note 1), ¶ 238, 68.

⁶⁸Sturgeon (note 67) 273; Faraday (note 67), ¶ 238, 68.

⁶⁹George Bachhoffner, Popular Treatise on Voltaic Electricity and Electro-Magnetism (London, 1838), 32.

⁷⁰Sturgeon (note 67) 275.

⁷¹Morus (note 5) portrays the Sturgeon–Faraday split differently, along class and strategic lines. For him, Sturgeon concentrated on elucidating apparatus and communicating to electrical practicioners; Faraday crafted an elite image for himself by highlighting results and hiding his manual labour.

⁷²Faraday, ‘Observations on Mental Education’, Lectures on Education (London 1859), 36–88, quote p. 58.

⁷³Nicholas Callan, ‘On the Best Method of Making an Electro-Magnet for Electrical Purposes, and on the Vast Superiority of the Electric Power of the Electro-Magnet, over the Electric Power of the Common Magneto-Electric Machine’, Annals of Electricity, 1 (1837), 295–302, quote 295

⁷⁴Although Callan did not explain why the coils’ opposite (not same) ends are combined, this measure is necessary to preserve the same winding sense throughout and to prevent the cancelling of current effects. This issue is discussed in the context of other historical replications, Cavicchi (note 24, note 28).

⁷⁵N. J. Callan, ‘On a new Galvanic Battery’, Philosophical Magazine, 9 (1836), 472–78. .

⁷⁶For student memories of Professor Callan, see McLaughlin (note 8), 35–54, quote 37.

⁷⁷Callan (note 75) 476.

⁷⁸Nicholas Callan, ‘On the Best Method of Making an Electro-Magnet for Electrical Purposes, and on the Vast Superiority of the Electric Power of the Electro-Magnet, over the Electric Power of the Common Magneto-Electric Machine’, Annals of Electricity, 1 (1837), 295–302, quote 295.

⁸⁰Nicholas Callan (note 78), 297.

⁷⁹Although Callan did not cite it, his battery with its 20 pairs of large plates that could be connected (in our terms) all series, all parallel, or in combinations, resembles that of Robert Hare, ‘A New Theory of Galvanism … by means of the Calorimotor, a new Galvanic Instrument’, American Journal of Science, 1 (1818), 412–23.

⁸¹Callan (note 78), 299.

⁸²Callan (note 78), 300. Callan's original horseshoe is preserved at the Museum of St. Patrick's College, Maynooth, Ireland. See Charles Mollan and John Upton, The Scientific Apparatus of Nicholas Callan and Other Historic Instruments (Maynooth 1994), no. 068, 62–64.

⁸³N. J. Callan, ‘A Description of an Electromagnetic Repeater or of a Machine by Which the Connection Between the Voltaic Battery and the Helix of an Electromagnet May Be Broken and Renewed Several Thousand Times in the Space of One Minute’, Annals of Electricity, 1 (1837), 229–30.

⁸⁴McLaughlin (note 8), 70.

⁸⁵N. J. Callan, ‘A Description of the Most Powerful Electro-Magnet Yet Constructed’, Annals of Electricity, 1 (1837), 376–78.

⁸⁶In asserting his priority, Page (note 14), 15–18 tabulated the publication dates of his papers and Callan's.

⁸⁷N. J. Callan, ‘A Description of the Most Powerful Electro-Magnet Yet Constructed’, Journal of the Franklin Institute, 21 (1838), 57–59.

⁸⁸‘Medical Miscellany’, Boston Medical and Surgical Journal (26 April 1837), 195.

⁸⁹Deaths, Columbian Centinel, 16 March 1839. His death was also noted ‘In Boston, Dr. William King, electrician, 78’ in the Boston Medical and Surgical Journal (3 April 1839), 132.

⁹⁰Philosophical Apparatus, Boston Atlas, 16 April 1839.

⁹¹Fair of the Mechanic Association, Boston Daily Evening Transcript, 23 September 1837, 1.

⁹²Mammoth Magnet, Boston Daily Evening Transcript, 20 December 1837.

⁹³Mammoth Magnet, Boston Medical and Surgical Journal (20 December 1837), 322.

⁹⁴Charles Grafton Page, ‘New Magnetic Electrical Machine of Great Power … ’, American Journal of Science, 34 (1838), 163–169.

⁹⁵Page (note 94), 168. Sturgeon and George Bachhoffner established that bundled iron wires amplify shock, independently of Page and each other (see section 8).

⁹⁶Page's compound electromagnet is first described in ‘New Magnetic Electrical Machine of great power … ’, American Journal of Science, 34 (1838), 163–69; quote 168. At the end of his reprinting of this paper, Sturgeon added a footnote referencing his prior research of different iron wire cores.

⁹⁷Charles G. Page, ‘Researches in Magnetic Electricity and new Magnetic Electrical Instruments’, American Journal of Science, 34 (1838), 364–73, quote p. 367. Here, Page also expanded his ideas about the neutralizing magnetism of iron or steel wires in the core bundle (p. 368).

⁹⁸Cavicchi (note 28), Chapter 20. I was familiar with the double-helix coil of Page's associate Boston instrument maker Daniel Davis Jr in the Collection of Historical Scientific Instruments at Harvard (# 0118). Davis worked skilfully enough that the winding itself preserves a hollow, whereas mine did not.

⁹⁹The HP Infinitum oscilloscope was used with a Textronics P6015 high-voltage probe. For more discussion on using electronic test equipment in substituting for historical shocks, and for the star wheel interrupter, see the references in note 43.

¹⁰⁰Sturgeon's talk and demonstration occurring on June 24, 1837 was noticed in Annals of Electricity, 1 (1837), quote 417, and ‘First Annual Report’, Transactions and Proceedings of the London Electrical Society, 1837–1840. Bachhoffner also credited Callan's gift coil with being an instigator of his own, ‘On the Electro-magnetic Machine’, Annals of Electricity, 2 (1838), 207–13, footnote p. 207.

¹⁰¹Baird (note 20) 3–4, quote p. 213.

¹⁰²That Sturgeon could not accept Callan's device without reworking it echoes Keith Pavitt's 1999 observation that ‘there are very few technological free lunches. Even borrowers of technology must have their own skills and make their own expenditures’, quoted p. 1255 in ‘What do we know about innovation’, editorial, Research Policy, 33 (2004), 1253–58. A related discussion of scientists’ differing individual views and shared understandings is found in Kenneth Caneva, The Form and Function of Scientific Discoveries. (Washington, DC, 2001).

¹⁰³William Sturgeon, ‘An experimental investigation of the influence of Electric Currents on Soft Iron …’, Annals of Electricity, 1 (1837), 470–84, quote 478; reprinted in Sturgeon 1850 (note 46) 298–309.

¹⁰⁴William Sturgeon, ‘On the production of secondary electric currents in a metallic spiral, independently of opening and shutting the Battery circuit; or, of giving motion to either the primitive or secondary conducting wires, Annals of Electricity, 2 (1838), 109–12; reprinted in Sturgeon 1850 (note 46), 322–24.

¹⁰⁵Sturgeon (note 103), p. 484.

¹⁰⁶Sturgeon 1850 (note 46), quote p. 309. His footnote (p. 289) states that he demonstrated this coil to the London Electrical Society on 5 August 1837. See also his retrospective synopsis of this paper, pp. 46–47.

¹⁰⁷N. J. Callan, ‘On a method of connecting electromagnets so as to combined their electric powers, &c. … ’, Annals of Electricity, 1 (1837), 491–94.

¹⁰⁸The quote from Sturgeon is his editorially signed footnote to Callan's paper (note 103), 493. J. A. Fleming misattributed the footnote to Callan (note 6), p. 12. On this misinformed basis, Fleming credited Callan with the invention of the induction coil: ‘it is to Callan that we owe this simple piece of apparatus, now found in every physical laboratory … having two separate wires, one thick and the other thin’.

¹⁰⁹Page (note 97), 365.

¹¹⁰Page (note 97), 365.

¹¹¹Page (note 97), 366.

¹¹²Page (note 97), 372.

¹¹³Page (note 97), 372.

¹¹⁴Page's ‘Compound Electromagnet and Electrotome’ is described in ‘Magneto-Electric and Electro-Magnetic Apparatus and Experiments’, American Journal of Science, 35 (1839), 252–68. One of Davis’ productions of it is on display in the National Museum of American History (cat. 309,254) in Washington, DC.

¹¹⁵Davis’ ‘Double Helix and Electrotome’ was reported by Joseph Hale Abbot in ‘A Description of Several New Electromagnetic and Magneto-Electric Instruments and Experiments’, American Journal of Science, 40 (1841), 104–11. Both instruments are listed in Davis’ Catalogue for 1842; only the one with a faster clockwork interrupter is discussed in his Manual of Magnetism (Boston, 1842), 251–53 and included in the Catalogue of Apparatus (Boston, 1848). The patent model, submitted decades later on 14 April 1868 as part of patent no. 76 654, is displayed at the Smithsonian's National Museum of American History, catalogue no. 309 254; accession no. 89 797. For patent history, see Post (note 10).

¹¹⁶Double coils based on the Page–David instruments were listed in catalogues by Joseph Wightman, Catalogue (Boston, 1842), and Benjamin Pike, Illustrated Descriptive Catalogue (New York, 1856). Physician William Channing described and illustrated use of Page-Davis double coils in Notes on the Medical Application of Electricity (Boston, 1849). Many Page–Davis instruments are in the Smithsonian National Museum of American History, the Collection of Historical Scientific Instruments at Harvard, and other college museums. A compilation is available at http://www2.kenyon.edu/depts/physics/EarlyApparatus/

¹¹⁷Page stated ‘very little transpired on the subject of induction coils from 1842 until 1850’ in (note 14), 41.

¹¹⁸The Dartmouth instrument, accession number 2002.1.35088, was listed in an 1870s Dartmouth inventory as ‘Page's apparatus for shocks with mercury break’. This coil, with its possible links to Page and Davis, is described in David Pantalony, Richard L. Kremer and Francis J. Manasek, Study, Measure, Experiment: Dartmouth's Allen King Collection of Scientific Instruments (Norwich, VT, 2005), 157–159.

¹¹⁹Page (note 94), p. 168.

¹²⁰J. C. Nesbit, ‘On Electro-magnetic Coil Machines’, Annals of Electricity, 2 (1838), 203–205, quote 203.

¹²¹George Bachhoffner, ‘On the Electro-magnetic Machine’, Annals of Electricity, 1 (1837), 207–213, quote p.

¹²⁶W. Sturgeon, ‘Answer to Mr. Nesbit's Letter’, Annals of Electricity, 2 (1838), 205–206.

¹²²Charles Barker, ‘To the Editor of the Annals of Electricity, Magnetism & Chemistry, Annals of Electricity, 1 (1837), 157–159.

¹²³Sturgeon (note 103), 480.

¹²⁴Nesbit (note 120), 204.

¹²⁵Uriah Clarke, ‘On the Electro-magnetic Coil Machines. In a Letter to the Editor’, Annals of Electricity, 3 (1838), 12–13.

¹³⁰Bachhoffner (note 121), 213.

¹²⁷Morus (note 5), 81–82.

¹²⁸An unsigned footnote to Bachhoffner's paper claimed the presentation of a coil at the London Electrical Society meeting ‘on August 5, 1837 … was, I believe, the first of the kind exhibited in public … ’; Bachhoffner, (note 121), footnote p. 207. Was this footnote written by Sturgeon? See note 106.

¹²⁹Bachhoffner (note 121), 207–208.

¹³¹Bachhoffner (note 69).

¹³²George Bachhoffner, ‘A Letter to W. Sturgeon, Esq.’, Annals of Electricity, 1 (1837), 496–97; quote 497. Bachhoffner's estimate of a twenty-fold increase in power due to the insulated iron wire core is noted in Annals of Electricity, 2 (1838), 73 and Bachhoffner, ‘A Description of the Different Arrangements of the Electro-magnetic Coil, and the Influence of a Spiral Conductor in Increasing the Power of a Voltaic Current’, presented 28 October 1837’, Proceedings of the London Electrical Society (1840), 132–33.

¹³³Bachhoffner (note 121), 212.

¹³⁴Bachhoffner (note 121), 213.

¹³⁶William Sturgeon, ‘Description of Three Different Instruments for Opening and Shutting the Battery Circuit of an Electro-magnetic Coil Machine’, Annals of Electricity, 3 (1838), 31–35, quote 35.

¹³⁵Page (note 41), 140. For a replication, see Cavicchi, ‘Sparks, Shocks and Voltage Traces … ’ (note 43).

¹³⁷Bachhoffner called himself ‘a chemist and not an artist’ Chemistry as Applied to the Fine Arts (London, 1837), 167.

¹³⁸Bachhoffner (note 121), 210–11.

¹³⁹Edward Palmer, ‘Catalogue of Electro-magnetic and Voltaic Apparatus’ (London 1838), bound with Bachhoffner (note 69). Palmer, an ironmonger's guild member, had a shop from 1838–1845 at 103 Newgate St. London; Clifton (note 7), 207.

¹⁴⁰An example of E. M. Clarke's ‘Lockey coil’ with interchangeable blades and discs, is in the Moosnick Medical and Science Museum at Transylvania University, Lexington, Kentucky.

¹⁴¹F. Lawrence Holmes considered the pathway, its limitations, and alternative metaphors for representing an individual scientist's experimental work in Investigative Pathways: Patterns and Stages in the Careers of Experimental Scientists (New Haven 2004).

¹⁴²See Holmes (note 141) for related observations on episodic and ongoing features of investigation in scientific careers.

¹⁴³Sturgeon (note 46), 75.