No CrossRef data available.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
Published online by Cambridge University Press: 05 January 2009
The magnetic circuit model acts as a unifying principle in descriptive magnetostatics, and as an approximate computational aid in electrical machine design. It was the subject of repeated rediscoveries through the period 1855 to 1886, taking different forms and being provided with different justifications but all motivated by the mathematical difficulty of existing magnetic theory. The process culminated in several competitively-slanted announcements of the principle made during 1884 to 1886, arising in connection with the already comparatively efficient designs of contemporary dynamos which made its application plausible. The preferred conceptual imagery, of induction flow against a ‘resistance’, originated in the magnetic theories of Faraday, though these underwent considerable changes before adoption.
1 Representative texts from the recent epoch are: Hughes, E., Electrical Technology, London, 1977Google Scholar; Hayt, W.H., Engineering Electromagnetism, N. York, 1974Google Scholar; Lorrain, P. and Carson, D., Electromagnetic Fields and Waves, San Francisco, 1970Google Scholar; Parker, R.J. and Studders, R.J., Permanent Magnets and their Application, New York, 1962.Google Scholar
2 Jordan, D.W., ‘D.E. Hughes, self-induction and the skin effect’, Centaurus, (1982), 26, pp. 123–153CrossRefGoogle Scholar; ‘The adoption of self-induction by telephony’, Annals of Science, (1982), 39, pp. 433–461Google Scholar; ‘The cry for useless knowledge: education for a new Victorian technology’, IEE Proceedings, (1985), 132 Part A, pp. 587–601Google Scholar; ‘Maxwell's electrodynamics and British electrical engineers in the 1880s’, Proceedings of the Symposium on the History of Science, Technology and Society, 1750–1914, September, 1989, University of Ulster.Google Scholar
3 Thompson, S.P., Dynamo-Electric Machinery, 1st edn, London, 1884.Google Scholar
4 Thompson, S.P., ‘The Electromagnet’ (Four Cantor Lectures), Journal for the Society of the Arts, (1889–1890), 38, pp. 861–905, 909–926, 929–946, 949–970.Google Scholar
5 Thompson, S.P., Electro-Magnets and Electro Magnetic Mechanism, London, 1891Google Scholar; and Dynamo-Electric Machinery, (4th edn, 1892 onward), London.Google Scholar
6 Jordan, , op. cit. (2)Google Scholar, ‘The cry for useless knowledge’.
7 Thompson, , op. cit. (4), p. 862.Google Scholar
8 Idem.
9 Proceedings of the National Conference of Electricians, Philadelphia, 8th to 13th September 1884, New York, 1885, p. 147.Google Scholar
10 See for example Ayrton, W.E., Perry, J., ‘On winding electromagnets’, Proceedings of the Physics Society of London, (1882–1884), 5, pp. 230–234CrossRefGoogle Scholar; Thomson, J.J., Newall, H.F., ‘Experiments on the maximum of magnetism of iron rods, especially on the effect of narrow crevasses at right angles to the length’, Proceedings of the Cambridge Philosophical Society, (1886–1889), 6, pp. 84–90Google Scholar; Ewing, J.A., Magnetic Induction in Iron and Other Metals, London, 1891 (chapter X).Google Scholar
11 Thompson, S.P., Dynamo-Electric Machinery, (5th edn), London, 1896.Google Scholar
12 Thompson, S.P., ‘On the law of the electromagnet and the law of the dynamo, Philosophical Magazine, (1886), V, 21, pp. 1–10.Google Scholar Also ‘Further notes on the formulae of the electromagnet and the equations of the dynamo’, Philosophical Magazine, (1886), V, 22, pp. 76–86Google Scholar, in reply to Frölich, O., ‘Das Gesetz des Elektromagneten’, Elektrotechnische Zeitschrift, (1886), 7, pp. 163–165.Google Scholar
13 The following are representative of a very large output by Frölich: ‘Versuche mit dynamoelektrischen Maschinen und elektrische Kraftübertragung und theoretische Folgerungen aus deselben’, Elektrotechnische Zeitschrift, (1881), 2, pp. 134–175Google Scholar; ‘Versuche des Establissements von Siemens und Halske iiber dynamoelektrische Maschinen und elektrische Kraftübertragung und theoretische Folgerungen aus deselben’, Elektrotechnische Zeitschrift, (1880), 2, pp. 170–175.Google Scholar
14 This is Frölich's ‘curve of active magnetism’; it is ‘the same for all machines, and the only individual feature is the scale on which the abscissae are plotted’: Frölich, O., Die dynamoelektrische Maschine, Berlin, 1886, p. 11.CrossRefGoogle Scholar
15 Frölich, O., Die Lehre der Elektricität und dem Magnetismus, Berlin, 1876.Google Scholar
16 Ayrton, W.E., The Electrician, (1885–1886), 16, pp. 31–35.Google Scholar (Copies of correspondence between Ayrton and John Perry, of Jan. 1879: the reply is wrongly dated. Perry suggested the correct form for the required formula.)
17 Thompson, , op. cit. (12)Google Scholar, ‘On the law of the electromagnet’.
18 Thompson's theory was based on ‘a forgotten theory’ by von Lament, J., Handbuch der Magnetismus, Leipsig, 1867.Google Scholar
19 Original Papers of the late John Hopkinson Vol. 1 (Technical Papers), Cambridge, U.K. 1901.Google Scholar (See J. and Hopkinson, E., ‘Dynamo-Electric Machinery’, pp. 84–101Google Scholar, first published in Part 1 of Philosophical Transactions in 1886.)
20 The most penetrating biography was written by his son, B. Hopkinson, as a preface to the collected works: Hopkinson, B. ‘Memoir’, op. cit. (19), pp. (ix)–(lxii)Google Scholar. See also Proceedings of the Royal Society, (1898), 17, pp. (xvii)–(xxiv)Google Scholar, and Greig, J., John Hopkinson: Electrical Engineer, London, 1970.Google Scholar An evaluation by a contemporary of his magnetic work is in Ewing, A., An Engineer's Outlook, London, 1933.Google Scholar For an overview of his pure-scientific work see: Hopkinson, J., Original Papers by the Late John Hopkinson Vol. 2 (Scientific Papers), Cambridge, U.K., 1901.Google Scholar
21 Hopkinson, B., op. cit. (19), pp. (xx) and (xxiv).Google Scholar
22 Jordan, , op. cit. (2)Google Scholar, ‘The cry for useless knowledge’.
23 Higgs, W.H.P., Brittle, J.R., ‘Some Recent Improvements in Dynamo Design’, Minutes of the Proceedings of the Institute of Civil Engineers, (1877–1878), 52 Part II, pp. 36–98.CrossRefGoogle Scholar
24 Hopkinson, B., op. cit. (19), p. (xl).Google Scholar
25 Siemens, A., ‘On some recent improvements in electrical lighting apparatus’, Journal of the Society of Telegraph Engineers, (1880), 9, pp. 89–114, 136–162.CrossRefGoogle Scholar
26 Hopkinson, B., op. cit. (19), p. (xliii).Google Scholar
27 Hopkinson, J., op. cit. (19), pp. 57–83.Google Scholar
28 Kapp, G., ‘Modern continuous-current dynamo-electric machines and their engines’, Minutes of the Proceedings of the Institute of Civil Engineers, (1885–1886), 83 Part I, pp. 123–274.CrossRefGoogle Scholar (See Discussion pp. 229–236.)
29 Ibid, p. 232. The diagrams comparing the old and new machines have become crossed over.
30 Thompson, S.P., Dynamo Electric Machinery, London, 1896.Google Scholar
31 Hopkinson, , op. cit. (28), p. 230 (Discussion).Google Scholar
32 Hopkinson, J., ‘Magnetisation of iron’, Philosophical Transactions, (1885), 176 Part 2, pp. 455–469.CrossRefGoogle Scholar An extract only is given in the Original Papers, op. cit. (19); the paper is given in full in vol ii, op. cit. (20), pp. 154–177. Hopkinson claimed (op. cit. (28)) that as early as November 1884 he ‘had sent a paper on these questions to the Royal Society’, but ‘Magnetisation of iron’ is headed ‘Received April 15th, 1885’.
33 See the footnote on the first page of a sequel to ‘Dynamo-electric machinery’: op. cit. (19), pp. 122–132.Google Scholar (First published as Hopkinson, J. ‘Dynamo-Electric Machinery’ in Proceedings of the Royal Society, (1892).)Google Scholar
34 Tucker, D.G.Gisbert Kapp 1852–1922, Birmingham, U.K., 1972.Google Scholar
35 Kapp, G. ‘On the design and construction of dynamos’. The Electrician (1884–1885), 15, pp. 259, 307–309, 346–347, 390–391, 430–431, 511–513Google Scholar; (1885–86), 16, pp. 23–5, 190–191, 250–252; (1886–87), 17, pp. 7–9, 406–407.
36 Kapp, G., Dynamos, Alternators and Transformers, London, 1893.Google Scholar
37 Kapp, , op. cit. (28).Google Scholar
38 Kapp, G., ‘The pre-determination of the characteristics of a dynamo’. Journal of the Society of Telegraph Engineers and Electricians, (1886), 15, pp. 518–595.CrossRefGoogle Scholar
39 Kapp, , op. cit. (28), p. 135.Google Scholar
40 Ibid., pp. 136 ff.
41 Ibid., pp. 137–138.
42 Kapp, , op. cit. (38).Google Scholar
43 Kuhn, T.S., The Essential Tension, Chicago, 1977.Google Scholar (See ‘Second thoughts on paradigms’, pp. 293–319.)
44 du Bois, H., The Magnetic Circuit in Theory and Practice, London, 1896Google Scholar (a translation from lectures given to the International Congress of Electricians, Frankfort, 1891).
45 du Bois, H.E.J.G., ‘Magnetic circuits and their measurements’, The Electrician, (1891), 27, pp. 634–636.Google Scholar
46 Bosanquet, R.H.M., ‘On the use of the term ‘Resistance’ in the description of physical phenomena’. Philosophical Magazine, (1888), V, 25, pp. 419–425.Google Scholar
47 Carter, E.T., ‘The magnetic circuit’, The Electrician, (1890), 25, pp. 231–232.Google Scholar Also various comments, 4th July and 11th July issues.
48 Perry, , op. cit. (38), p. 584Google Scholar (Discussion); also Ayrton, op. cit. (16).Google Scholar
49 ‘Sir James Swinburne’, Biographical Memoirs of the Royal Society, London, 1958, pp. 253–268.Google Scholar
50 Swinburne, , op. cit. (38), p. 541Google Scholar (Discussion).
51 Jordan, , op. cit. (2)Google Scholar, ‘The cry for useless knowledge’.
52 Kapp, . op. cit. (38).Google Scholar
53 Thomson, W.Reprint of Papers on Electricity and Magnetism, 2nd edn, London, 1884.Google Scholar (See p. 336, footnote, and p. 393.)
54 Op. cit. (28), p. 217 (Discussion).Google Scholar
55 Jordan, , op. cit. (2)Google Scholar, ‘The cry for useless knowledge’, and Brock, W.H., ‘The Japanese connection’, British Journal for the History of Science, (1981), 14, pp. 227–243.CrossRefGoogle Scholar
56 ‘A list of the publications of the late Professor Ayrton F.R.S., etc.’ The Central (the magazine of the student society of the City and Guilds Central Institution, London), (7th 04, 1910), pp. 92–97.Google Scholar
57 Kapp, , op. cit. (28). p. 124.Google Scholar
58 Quoted in Philosophical Magazine, (1884), V, 18, p. 153.Google Scholar
59 Crompton, R.E., Reminiscences, London 1982, pp. 102–105.Google Scholar
60 The Physical Papers of Henry Augustus Rowland, Baltimore, 1902Google Scholar (this contains a biographical preface by T.C. Mendenhall). Various aspects of Rowland's work in electrodynamics are evaluated in Buchwald, J.Z., From Maxwell to Microphysics, Chicago, 1985Google Scholar; and Miller, J.D., ‘Rowland and the nature of electric currents’, ISIS, (1972), 63, pp. 5–27.CrossRefGoogle Scholar
61 Rowland, H.A., ‘On magnetic permeability, and the maximum of magnetism of Iron, steel and nickel, Philosophical Magazine, (1873), IV, 46, pp. 140–159Google Scholar (or The Physical Papers, op. cit. (60), p. 35–53).Google Scholar
62 Rowland, , op. cit. (60)Google Scholar, Physical Papers, and Miller, J.D., ‘Rowland's magnetic analogue to Ohm's law, ISIS, (1975), 66, pp. 230–241.CrossRefGoogle Scholar
63 Rowland, H.A., ‘On the magnetic permeability and the maximum of magnetism of nickel and cobalt’, Philosophical Magazine, (1875), IV, 48, pp. 321–340Google Scholar (or The Physical Papers, op. cit. (60), pp. 56–74).Google Scholar
64 Rowland, H.A., ‘Studies on magnetic distribution’, Philsophical Magazine, (1874), IV, 50, pp. 257–277, 451–459Google Scholar (Physical Papers, op. cit. (60), pp. 89–127).Google Scholar
65 Green, G., An Essay on the Application of Mathematical Analysis to the Theories of Electricity and Magnetism, Nottingham, U.K. 1828Google Scholar; or Ferrars, M. (ed.), Mathematical Papers of George Green, New York, 1870.Google Scholar
66 Biot, B., Traité de Physique Expérimental et Mathématique, 4 vols, Paris, 1816Google Scholar. See vol. iii, p. 77.
67 Rowland, , op. cit. (60), Physical Papers, p. 90.Google Scholar
68 Rowland, , op. cit. (63).Google Scholar
69 Rowland, , op. cit. (64), pp. 89–90.Google Scholar
70 Thomson, W., ‘On the theory of the electric telegraph’ Proceedings of the Royal Society, (1855), 7, pp. 382–399CrossRefGoogle Scholar; and Kempe, A.B. ‘On the leakage of submarine cables’ Journal of the Society of Telegraph Engineers (1875), 4, pp. 90–97.CrossRefGoogle Scholar
71 Miller, , op. cit. (62).Google Scholar
72 ‘The National Conference of Electricians, Philadelphia’, Telegraphic Journal and Electrical Review, (1884), 15, pp. 299–308, 330–332, 348–351, 368–371, 384–386, 427.Google Scholar This source is the fullest immediate account from a British source: op. cit. (78) below for the complete transcript. (In ‘The theory of the dynamo’ from The Physical Papers, op. cit. (60), pp. 219–235Google Scholar, the formula is misprinted.)
73 Rowland, , op. cit. (72).Google Scholar
74 The Electrician (1884), 13, pp. 516–518, 535–538.Google Scholar
75 For example, du Bois, , op. cit. (44)Google Scholar, The Magnetic Circuit and Sharlin, H.I., The Making of the Electrical Age, N. York, 1963.Google Scholar
76 Thompson, S.P., Elementary Lessons in Electricity and Magnetism, London, 1908.Google Scholar
77 J.S. and Thompson, H.G., Silvanus Phillips Thompson, his Life and Letters, London, 1920, p. 120.Google Scholar
78 Proceedings of the National Conference of Electricians, Philadelphia, September 8–13, 1884, N. York, 1885.Google Scholar (Also published as Records of the …, Washington, 1886, which was the edition owned by S.P. Thompson.)
79 Information courtesy of the I.E.E. Archives Section, London.
80 Op. cit. (28 and 38).
81 Thompson, , op. cit. (3).Google Scholar
82 See Section X below.
83 Bosanquet, R.H.M., ‘On magnetomotive force’, Philosophical Transactions, (1883), V, 15, pp. 205–217. (See p. 205.)Google Scholar
84 Bosanquet, R.H.M., ‘Electromagnets II. On the magnetic permeability of iron and steel, with a new theory of magnetism’, Philosophical Transactions, (1885), v, 19, pp. 73–94. (See p. 73.)Google Scholar
85 Swinburne, , op. cit. (38), p. 544.Google Scholar
86 For example, Bosanquet, , op. cit. (83)Google Scholar; and Bosanquet, R.H.M., ‘On permanent magnetism’, Philosophical Magazine, (1887), V, 22, pp. 257–259 and 309–316Google Scholar; ‘On permanent magnets’, Philosophical Magazine, (1884), V, 18, pp. 142–153Google Scholar; and ‘Electromagnets VII: the law of the electromagnet and the law of the dynamo’, Philosophical Magazine, (1887), V, 23, pp. 338–350.Google Scholar
87 Bosanquet, , op. cit. (83), p. 205.Google Scholar
88 Bosanquet, , op. cit. (86) ‘Electromagnets VII’, p. 340.Google Scholar
89 Bosanquet, , op. cit. (46).Google Scholar
90 Bosanquet's experiments were carried out alongside his theory; see, for example, Bosanquet, , op. cit. (89), (90), (92).Google Scholar
91 Swinburne, , op. cit. (50).Google Scholar
92 Ewing, , op. cit. (10).Google Scholar
93 du Bois, , op. cit. (44).Google Scholar
94 Bosanquet, , op. cit. (83) p. 205.Google Scholar
95 Bosanquet, R.H.M., ‘Preliminary paper on a uniform rotation machine; and on the theory of electromagnetic tuning forks’, Proceedings of the Royal Society, (1883), 34, pp. 445–447.CrossRefGoogle Scholar (See p. 446.)
96 Bosanquet, , op. cit. (86), ‘Electromagnets VII’, p. 340.Google Scholar
97 Manuscript seen by courtesy of the Library of the Royal Society of London.
98 Wise, M. Norton, ‘The flow analogy to electricity and magnetism. Part 1: William Thomson's reformulation of action at a distance’, Archive for the History of the Exact Sciences' (1981), 25, pp. 19–70.CrossRefGoogle Scholar
99 Thomson, op. cit. (53), pp 1–24Google Scholar, ‘On the uniform motion of heat in homogeneous solid bodies, and its connection with the mathematical theory of electricity’; first published anonymously in Cambridge Mathematical Journal in 1842 and reprinted Philosophical Magazine, 1854 (Part 1).
100 Niven, W.D. (ed.), The Scientific Papers of James Clerk Maxwell, vol. i, Cambridge, U.K. 1890.Google Scholar (See ‘On Faraday's lines of force’, pp. 155–229.)
101 Rowland, , op. cit. (63).Google Scholar
102 Faraday, M., Experimental Researches in Electricity, 3 vols, London, vol. i 1839, vol, ii 1844, vol. iii 1855.Google Scholar (All subsequent references are to vol. iii.)
103 Maxwell, J. Clerk, A Treatise on Electricity and Magnetism (2 vols), 3rd edn, Oxford, 1904.Google Scholar (See vol. ii, p. 176.)
104 For example Rowland, , op. cit. (60), pp. 24–27.Google Scholar
105 Hertz, H., Electric Waves, London, 1893, p. 21.Google Scholar
106 Buchwald, J.E., From Maxwell to Microphysics, Chicago, 1985.Google Scholar
107 Higgins, T.J., ‘The origins and development of the concept of inductance, the skin effect and the proximity effect’, American Journal of Physics, (1941), 9, pp. 337–346.CrossRefGoogle Scholar
108 Faraday, , op. cit. (102), n. 3231.Google Scholar
109 Ibid., n. 3070–3176 (‘On lines of magnetic force, their definite character; and their distribution within a magnet and through space’. Dated Oct. 1851). The technique was developed by Rowland, H.A., ‘Preliminary note on a magnetic proof plane’, American Journal of Science, (1875), 10, pp. 4–17.Google Scholar
110 Faraday, , op. cit. (102), n. 3215–3233Google Scholar (‘On the amount and general distribution of the forces of magnetism when associated with other magnets’. Dated Dec. 1851).
111 Ibid., n. 3218.
112 Ibid., n. 3223.
113 Ibid., n. 3231.
114 Ibid., n. 3226.
115 Ibid., n. 3227.
116 Ibid., n. 3230.
117 Thomson, and Newall, , op. cit. (10).Google Scholar
118 Faraday, , op. cit. (102), n. 3228.Google Scholar
119 Ibid., n. 3268.
120 Ibid., n. 3232.
121 Thomson, , op. cit. (53).Google Scholar
122 Faraday, , op. cit. (102), n. 3286.Google Scholar
123 Ibid., n. 3285.
124 Ibid., n. 3287.
125 Ibid., n. 3288.
126 Ibid., n. 3289. (Non-permanent magnets are also mentioned.)
127 Ibid., n. 2832, 3228, 3232, 3262, 3276, 3282, 3286, 3288.
128 Ibid., n. 2718–2796.
129 Ibid., n. 2797–2845.
130 Ibid., n. 2797.
131 Ibid., n. 2835.
132 A general appreciation of Ohm's life and achievement is found in: Lommel, E., ‘The scientific work of George Simon Ohm’, Smithsonian Reports (07 1891), pp. 247–256.Google Scholar A list of Ohm's papers, and of much associated work, is given by Schagrin, , op. cit. (134) belowGoogle Scholar. The memoir usually quoted in this connection is translated into English: Ohm, G.S.. ‘The galvanic circuit investigated mathematically’. From Taylor, R., Scientific Memoirs, vol. ii, London 1841Google Scholar; its sections are dated at various times in 1826 and 1827.
133 Winter, H.J.J., ‘The reception of Ohm's early researches by his contemporaries’, Philosophical Magazine, (1944), VII, 35, pp. 371–386.Google Scholar
134 Schagrin, M.L., ‘Resistance to Ohm's law’, American Journal of Physics, (1963), 31, pp. 536–547.CrossRefGoogle Scholar
135 Winter, , op. cit. (133)Google ScholarSchagrin, , op. cit. (134).Google Scholar
136 See for example the article and references in: ‘Physical Units’, Encyclopaedia Britannica, London 1950. The social-historical position of measurement is discussed with particular reference to W. Thomson by Wise, M. Norton and Smith, Crosbie, ‘Measurement, work and industry in Lord Kelvin's Britain’, Historical studies in the Physical Sciences, (1989), 17 Part 1, pp. 147–173.CrossRefGoogle Scholar
137 See, for example Harris, W. Snow, ‘On the correct interpretation of the electrical terms Intensity and Quantity’, Philosophical Magazine, (1863), 26, pp. 504–515Google Scholar; Clark, Latimer, ‘On electric quantities and intensities’ (Royal Institute lecture, 1861), Royal Institution Library of Science, Elsevier, 1970, pp. 365–369.Google Scholar
138 Ayrton, W.E., ‘On the terms ‘Tension’, ‘Intensity’ and ‘Quantity’, Telegraphic Journal, (1873), 18, pp. 107–108.Google Scholar
139 Thompson, S.P., Elementary Lessons in Electricity and Magnetism, 1st edn, London 1881.Google Scholar
140 Jordan, , op. cit. (2), 1982 and 1989.Google Scholar
141 Swinburne, , op. cit. (50).Google Scholar
142 Ayrton, W.E., Perry, J., ‘The magnetic circuit of dynamo machines’, Philosophical Magazine, (1888), V, 25, pp. 496–510.Google Scholar
143 For examples, Bidwell, Shelford, ‘On the lifting power of electro-magnets and the magnetisation of iron’, Proceedings of the Royal Society, (1886), 40, pp. 486–496.CrossRefGoogle Scholar
144 Hopkinson, , op. cit. (32),Google Scholar
145 Ewing, , op. cit. (92), chapter X.Google Scholar
146 Ayrton, , op. cit. (16).Google Scholar
147 Thompson, , op. cit. (4).Google Scholar
148 Cumming, J., ‘On the connection of galvanism and magnetism’, Transactions of the Cambridge Philosophical Society, 1821, pp. 269–279Google Scholar; and ‘On the application of magnetism as a measure of electricity’, ibid., pp. 282–286.
149 Elphinstone, Lord and Vincent, C.W., ‘On magnetic circuits in dynamo- and magneto-electric machines’, Proceedings of the Royal Society, (1880), 30, pp. 270–293.Google Scholar
150 Thompson, , op. cit. (4), pp. 862, 875.Google Scholar
151 Joule, J.P., The Scientific Papers of James Prescott Joule, London, 1884. See pp. 1–53.Google Scholar
152 Sturgeon, W., Scientific Researches in Electricity, Galvanism, Electro-Magnetism and Electro-Chemistry, London, 1850.Google Scholar (See pp. 42–43.)
153 Ibid., ‘A description of an electro-magnetic engine for turning machinery’, pp. 557–559Google Scholar and Plate XVIII. The description is dated Oct. 1836.
154 Joule, , op. cit. (151).Google Scholar
155 Thompson, S.P., Dynamo Electric Machinery, London 1884, p. 102.Google Scholar
156 Ibid., p. 105.
157 Thompson, S.P., Dynamo Electric Machinery, London 1896, p. 404, Fig. 274.Google Scholar
158 Dunsheath, P., A History of Electrical Engineering, London, 1962, p. 182.Google Scholar
159 Jordan, , op. cit. (2).Google Scholar
160 J. Tyndall, referee's report to the Royal Society on a paper by Joule entitled ‘Account of introductory researches on the induction of magnetism by electric currents’ submitted to Philosophical Transactions of the Royal Society 1855–1856. Royal Society references RR3 155 4th January 1855 (should read 1856) and RR3 15725th July 1855. See also M. Faraday, RR3 154 6th July 1855 and RR3 138 7th January 1856.