Faraday, Maxwell, and the Electromagnetic Field
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One purpose of these notes is to give sources. A second is to fill in some technical detail where it may be helpful. A third is to shed interesting sidelights, and we hope all readers will enjoy browsing through these pages.
ABBREVIATIONS FOR SOURCES
Bence Jones Bence Jones, Henry. The Life and Letters of Faraday. 2 vols. Philadelphia: Lippincott, 1870.
Campbell and Garnett Campbell, Lewis, and William Garnett. The Life of James Clerk Maxwell. 1st ed. London: Macmillan, 1882. Page numbers refer to the Sonnet Software online version of this book (second edition, 1999).
Hamilton Hamilton, James. Faraday: The Life. London: Harper Collins, 2002.
Harman (1990–2002) Harman, Peter M., ed. The Scientific Papers and Letters of James Clerk Maxwell. 3 vols. Cambridge: Cambridge University Press, 1990–2002.
James (1991–2011) James, Frank A. J. L., ed. The Correspondence of Michael Faraday. 6 vols. London: Institution of Engineering and Technology, 1991–2011.
Researches Faraday, Michael. Experimental Researches in Electricity. New York: Dover Publications, 1965.
Simpson Simpson, Thomas K. Maxwell on the Electromagnetic Field. New Brunswick, NJ: Rutgers University Press, 1997.
Thompson Thompson, Sylvanus P. Michael Faraday: His Life and Work. London: Cassell, 1901.
Williams (1965) Williams, L. Pearce, Michael Faraday: A Biography. New York: Basic Books, 1965.
INTRODUCTION
1. The Wheatstone bridge, a type of circuit used for measuring electrical resistance, has been named after Charles Wheatstone but was actually invented by a colleague, Samuel Christie. However, Wheatstone himself was a prolific inventor, and any spurious credit he gained from the bridge was offset when one of his many true inventions, a system for coding messages, became known as the Playfair cipher, after Lyon Playfair, a chemistry professor who took up politics, became a baron, and vigorously promoted the cipher for official use.
CHAPTER ONE: THE APPRENTICE
1. The epitaph is on Sandeman's tomb in Danbury, Connecticut. He emigrated to America in the 1760s.
2. The description of Faraday's “brown curls” is quoted by Thompson, page 4.
3. Faraday recollected his childhood belief in the Arabian Nights in an 1858 letter to Auguste de la Rive, given in Williams (1965), page 552.
4. This instruction by Watts can be found in The Improvement of the Mind, Also His Posthumous Works, page 44.
5. This instruction can also be found in The Improvement of the Mind, Also His Posthumous Works, on page 33.
6. Faraday described his electrical experiment with a solution of Epsom salts in a long letter to Benjamin Abbott on July 1812, given in Bence Jones, vol. 1, pages 16–22.
7. The remark about Davy's eyes is reported in John Davy's book Memoirs of the Life of Sir Humphry Davy, page 136.
8. The “no answer required” incident is reported in James (1991–2001), vol. 1, page xxx.
9. This despondent passage is from Faraday's October 18, 1812, letter to his friend John Huxtable, given in Bence Jones, vol. 1, pages 44–46.
10. Faraday recollected Davy's warning that science was a harsh mistress in an 1829 letter to Davy's biographer John Ayrton Paris. The complete letter can be found in Thompson, page. 10.
11. Instituted by Napoleon and formally designated the Volta Prize, this was an award for research in electrochemistry and had a cash value of 3,000 francs.
12. Davy's letter about the Napoleon Prize is quoted by John Ayrton Paris in The Life of Sir Humphry Davy, page 406.
CHAPTER TWO: CHEMISTRY
1. Faraday's early observation on the French character can be found in Bowers and Symons's book Curiosity Perfectly Satisfied: Faraday's Travels in Europe, page 15.
2. Faraday's slightly later observation of the French character is from his August 6, 1814, letter to Benjamin Abbott's brother, Robert Abbott, given in James (1991–2011), vol. 1, page 80.
3. Faraday expressed this opinion of Lady Davy in a letter on January 25, 1815, to Benjamin Abbot, given in Williams (1965), page 40.
4. Faraday wrote to Benjamin Abbott about the French chemists on February 23, 1815. The letter is given in James (1991–2011), vol. 1, page 128.
5. Faraday commented on the Italian people in an August 6, 1814, letter to Robert Abbott, given in James (1991–2011), vol. 1, page 81.
6. Davy's impressions of Volta are quoted by John Ayrton Paris in The Life of Sir Humphry Davy.
7. The incident at the Marcets’ dinner party is related by Alan Hirshfeld in The Electric Life of Michael Faraday, page 53. Hirshfeld cites as his source Bowers and Symons's Curiosity Perfectly Satisfied: Faraday's Travels in Europe.
8. The quotation “We loved Faraday” is from the booklet by M. Dumas (secretary of the Institut Impérial de France), Éloge historique de Michel Faraday.
9. Faraday's journal entry about Bonaparte was on March 7, 1815, and is given in Bence Jones, vol. 1, page 115.
10. Faraday wrote this letter to his mother on April 16, 1815. It is given in James (1991–2011) vol. 1, page 128.
11. Faraday's early observations to Benjamin Abbott on the art of lecturing were in a June 13, 1813, letter, given in James (1991–2011), vol. 1, pages 60–63.
12. Berzelius's publication of his censure of Davy is reported in Williams (1965), page 45.
CHAPTER THREE: HISTORY
1. William Gilbert made his comments about “miracle-mongering” in his book De Magnete, page 77.
2. The torsion balance was a kind of torsion pendulum, constructed so that electric or magnetic forces of attraction or repulsion could be measured by the twisting of the wire that held the pendulum bob.
3. Newton wrote this letter in 1692. Richard Bentley was a classical scholar and theologian who, a few years later, became master of Trinity College, Cambridge. It is given in W. D. Niven's The Scientific Papers of James Clerk Maxwell, vol. 2, page 316.
4. Ampère's explanation of why it took so long to discover the magnetic effect of an electric current is published Louis de Launay's Corréspondance du Grand Ampère, vol. 2, page 556.
5. Oersted wrote that the electric conflict performs circles in his paper “Experiments on the Effect of a Current of Electricity on the Magnetic Needle,” published in Annals of Philosophy, vol. 16, pages 237–277.
CHAPTER FOUR: A CIRCULAR FORCE
1. The poem ending “’tis love” is on page 73 in vol. 1 of Faraday's Common Place Book, held by the Institution of Engineering and Technology, London, and is quoted in Williams (1965), pages 96–97.
2. Faraday wrote this letter to Sarah on July 5, 1820. It is given by Bence Jones, vol. 1, page 317.
3. Faraday's journal entry for this day can be found in Bence Jones, vol. 1, pages 319–20.
4. Faraday wrote to Sarah on August 14, 1863, describing her as “a pillow to my mind,” as reported in Frank A. J. L. James's Michael Faraday: A Very Short Introduction, page 15.
5. Faraday wrote this letter to Ampère on September 3, 1822. It is given in James (1991–2011), vol. 1, pages 287–88.
6. George's recollection of this moment is reported in Bence Jones, vol. 1, page 345.
7. This journal entry is reported in Gooding and James's book Faraday Rediscovered, page 120.
8. Faraday included this comment in one of several letters on the theme of lecturing to Benjamin Abbott in June 1813. They are given in James (1991–2011), vol. 1, pages 55–65.
9. Faraday told Richard Phillips about his “nervous headaches” in a letter of August 29 1828, held in the Preussische Staatbibliotek, Berlin. The letter is quoted by Williams (1865), page 102.
10. Tyndall's summary of Sergeant Anderson's character, and Abbott's account of the boiler incident, are reported in Thompson, pages 96–97.
11. Faraday described his skepticism of theories in a letter to Ampère on February 2, 1822, given in Williams (1965), page 168.
12. Faraday's letter to Ampère, contrasting their working lives, was written on November 17, 1
825, and is given in James (1991–2011), vol. 1, page 392.
13. Faraday's letter to Davy's biographer is given in James (1991–2011), vol. 2, page 497.
CHAPTER FIVE: INDUCTION
1. The passage quoted is toward the end of a long letter from Faraday to Richard Phillips. The complete letter may be found in Thompson, pages 109–110.
2. Faraday published these thoughts on the electrotonic state in series 1 of his Researches, starting at paragraph 60.
3. Faraday used the expression “magnetic curves” in series 1 of his Researches, paragraph 114, but offered the alternative expression “lines of magnetic forces” in a footnote. The expression “lines of magnetic force” (suggesting a physical presence) then came to supersede the purely geometric “magnetic curves” in Faraday's writings.
4. Faraday expressed annoyance about the false accusation of plagiarism in a March 31, 1832, letter to William Jerden, given in James (1991–2001), vol. 2, page 29.
5. Faraday made his apology for “egotism” at the end of a long letter to Richard Phillips, mentioning, among other things, the electrotonic state. The complete letter may be found in Thompson, pages 114–17.
6. Faraday wrote his sealed note to the Royal Society on March 12, 1832. Its text can be found in James (1991–2011), vol. 2, letter 557.
7. Faraday expressed his agnosticism as to what a current actually was in series 3 of his Researches, paragraph 283.
8. Faraday summarized his theory of chemically equivalent weights in series 7 of his Researches, paragraph 869.
9. Helmholtz's words are quoted in Twentieth Century Physics, edited by L. Brown, B. Pippardi, and A. Pais, page 52.
10. The modern explanation of this process is in terms of electrons, which were not discovered for another sixty years. Each negatively charged ion arriving at the anode gives up one or more electrons and each positively charged ion arriving at the cathode receives one or more electrons.
11. John Tyndall described Faraday as “working at the boundaries of knowledge” in his book Faraday as a Discoverer, page. 73.
12. Faraday told Whewell about the rough reception the new terms had initially received in a letter on May 15, 1834, given in James (1991–2011), vol. 2, page 186.
13. The reference to Faraday's being “dimly aware” of the lateral repulsion between lines of force can be found in Thompson, page 165.
14. Electric lines of force always run from one charged body to another oppositely charged. So when two similarly charged bodies act on one another, the lines do not run between them but bend around, thus pushing away from one another. This sideways repulsion between the two sets of lines has the appearance of a direct repulsion between the two bodies. A similar sideways repulsion between magnetic lines of force explains why like magnetic poles repel one another.
15. Faraday gave this summary of his theory of the nature of electricity in series 14 of his Researches, paragraphs 1,669–1,678.
16. This passage is from Thompson, page 221. It follows the author's account of Faraday's unsuccessful attempt to detect the effect later discovered by Peter Zeeman, also described in our chapter 7.
CHAPTER SIX: A SHADOW OF A SPECULATION
1. Faraday's rueful comment on his loss of memory is reported in Bence Jones, vol. 2, page 142.
2. This comment, written on September 18, 1845, can be found in Faraday's Diary, vol. 4, page 227.
3. The giant electromagnet is described by Frank A. J. L. James in his book Michael Faraday, a Very Short Introduction, page 80.
4. Faraday presented this image of a man suspended in a magnetic field in series 20 of his Researches, paragraph 2,281.
5. The quoted words, including the earlier remark that the aether would have to be “destitute of gravitation but infinite in elasticity,” are from Faraday's letter to Richard Phillips on April 15, 1846, published the following month in the Philosophical Magazine with the title “Thoughts on Ray-vibrations” and reprinted in series 29 of his Researches.
6. The words quoted here are from the same letter to Richard Phillips, which also served as Faraday's article for the Philosophical Magazine, as cited above.
7. Tyndall's opinion of Faraday's “Ray-vibrations” is quoted by Thompson, page 193.
8. A fuller version of Faraday's letter to Oersted can be found in Bence Jones, vol. 2, page 268.
9. Faraday commented on his lateness in finding the magnetic effect of flames in an article in the Philosophical Magazine, 1847, vol. 31, page 401.
10. Faraday made this comment about space and matter in series 25 of his Researches, paragraph 2,787.
11. The passage quoted is from a letter Airy wrote to the Royal Institution's secretary, the Reverend John Barlow, in February 1855. The complete letter can be found in Bence Jones, vol. 2, page 353.
12. Faraday opened series 29 of his Researches, paragraph 3,070, with this reference to magnetic lines of force.
13. Faraday gave this description of what later became known as a tube of magnetic flux in paragraph 3,072 of series 29 of his Researches.
14. Faraday stated his law of electromagnetic induction in series 28 of his Researches, paragraph 3,115.
15. The right-hand rule: Point the thumb, first finger, and second finger of the right hand at right angles to each other. If the first finger represents the direction of the magnetic field and the thumb the direction of motion of the conductor, then the second finger will represent the direction of the electromotive force generated. A similar rule, but for the left hand, applies to motors. These rules were popularized by Ambrose Fleming.
16. Faraday carried out another experiment to demonstrate that lines of force ran all the way through a permanent magnet—reported in series 29 of his Researches, starting at paragraph 3,084.
17. Faraday wrote of the electrotonic state forcing itself on his mind in series 29 of his Researches, paragraph 3,269.
18. The third and last volume of Faraday's Researches covered series 19 to series 29.
19. Faraday made these observations on table turners in a letter to his friend Christian Friedrich Schönbein. A fuller version can be found in Thompson, page 252.
20. Faraday's letter expressing weariness with table turners is reported in Bence Jones, vol. 2, page 468.
21. Faraday's part-explanation for his failure to take on a pupil is in one of the miscellaneous notes found after his death. A fuller version can be found in Thompson, page 243.
22. This is the introduction to Maxwell's paper “On Faraday's Lines of Force,” Transactions of the Cambridge Philosophical Society, vol. 10, part 1. (Read on December 10, 1855, and February, 11, 1856).
23. Faraday's reply to Maxwell's first letter is given in Campbell and Garnett, page 252.
24. A complete copy of this November 9, 1857, letter from Maxwell to Faraday can be found in Campbell and Garnett's The Life of James Clerk Maxwell, 2nd ed. (London: Macmillan, 1884), page 203.
25. A complete copy of Faraday's November 13, 1857, reply to Maxwell can be found in Campbell and Garnett's The Life of James Clerk Maxwell, 2nd ed. (London: Macmillan, 1884), pages 205–206.
CHAPTER SEVEN: FARADAY'S LAST YEARS
1. A fuller version of Faraday's report of this visit to the South Foreland Lighthouse can be found in Williams (1965), page 491.
2. Faraday made this comment on mariners’ trust of lighthouses in a report on a proposal by Joseph Watson in 1854 for the use of a form of carbon-arc lamp in lighthouses. Faraday thought Watson's scheme was expensive and impracticable, and it was not adopted.
3. One of the leading advocates for the use of poison gas against the Russians in the Crimean War was the secretary of the Department of Science, Lyon Playfair, after whom the Playfair cipher was misleadingly named. The true inventor of this cipher was Charles Wheatstone, whose late defection from a Friday Evening Discourse at the Royal Institution led to Faraday's impromptu “Ray-vibrations” talk. See also note 1 to the introduction.
4. The extract is from evidence Faraday gav
e to the public-school commissioners in 1862. A fuller account of this episode can be found in Hamilton, pages 388–391.
5. Faraday wrote of his belief in a relation between gravity and electricity in his Researches, series 24, paragraph 2,717.
6. A shot tower is a tower built for the production of shot balls by free fall of molten lead.
7. Faraday recorded this final experiment in his laboratory notebook on March 12, 1862.
8. Faraday made this comment on honors to the Chancellor of the Exchequer, Thomas Spring Rice, in 1838. Thompson refers to the matter on page 271.
9. Faraday's comment about not wanting to be “a Sir” is quoted by Thompson, pages 273–74.
10. Instituted by Napoleon, this prize was formally designated the Volta Prize. See note 11 to chapter 1.
11. Faraday's comment about the Prussian knighthood is from the same letter in which he said he did not want to be “a Sir,” quoted by Thompson, pages 273–74.
12. Perhaps at a loss how to respond, Schönbein did not reply to Faraday's last letter.
13. Faraday mentioned that he wanted a simple funeral in a January 1866 letter to astronomer Sir James South, given in Bence Jones, vol. 2, page 478.
14. John Tyndall gives this description of Faraday in chapter 4 of his book Faraday as a Discoverer, page 37.
15. The extract is from Helmholtz's Faraday lecture to Fellows of the Chemical Society of London on April 5, 1881, quoted by Thompson, pages 282–83.
CHAPTER EIGHT: WHAT'S THE GO O’ THAT?
* Quoted passages in this chapter for which the source is not evident from the text or given a numbered note marker are from Campbell and Garnett.
1. The quoted line is from Robert Burns's poem “To a Mouse,” published in Poems, Chiefly in the Scottish Dialect (Kilmarnock: John Wilson, 1786).
2. David Forfar gives an excellent brief history of the Clerk and Cay families in his article “Generations of Genius.”
3. Maxwell's question “What's the go o’ that?” is reported by Campbell and Garnett, page 12.
4. A complete version of Maxwell's “Song of the Edinburgh Academician” can be found in Campbell and Garnett, pages 292–293.