Abstract
This part of the book contains all of Michell’s known letters. They are forty-four in number, not many. There are references to lost letters, but it does not seem that Michell maintained long correspondences. His closest colleague was probably Smeaton, whose Minute Book for 1782 and 1783, when he was largely in London, lists his many correspondents for those years; Michell is not among them. He often put off answering letters, as he acknowledged, and he spent a long time composing them. Several of his letters are very long; one of them he called a “paper.” Nearly all of his extant letters are about his main interest, science.
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Notes
- 1.
John Smeaton, Minute Book, London Journal, 1782 & 1783, Trinity House MSS 117.
- 2.
Michell to Blagden, 3 July 1787.
- 3.
Charles Mason, 1699–1771, D.D., fellow of Trinity College, Cambridge, from 1734 Woodwardian Professor of Geology in the University, F.R.S. 1742. D.A. Winstanley, Unreformed Cambridge (Cambridge: Cambridge University Press, 1935), 168–69.
- 4.
Gentleman’s Magazine 69 (1799): 112–13. The reason for the publication of this letter in February 1799, six years after Michell’s death, is unexplained.
- 5.
Benjamin Wilson, 1721–88, London portrait painter, electrical experimenter, F.R.S. 1751. G. L’E. Turner, “Wilson, Benjamin,” DSB 14: 418–20.
- 6.
Add Mss 30094: 86–87.
- 7.
Hermann Boerhaave, 1668–1738, professor of medicine, of chemistry, and of medicine and botany at the University of Leiden; his most influential publication, New Method of Chemistry, appeared in two editions, with corresponding English translations in 1727 and 1741. G.A. Lindeboom, “Boerhaave, Hermann,” DSB 2: 224–28. G.A. Lindeboom, Boerhaave and Great Britain: Three Lectures on Boerhaave with Particular Reference to His Relations with Great Britain (Leiden: E. J. Brill, 1974), 55–57.
- 8.
Gowin Knight, 1713–72, physician, magnetic experimenter, principal librarian of the British Museum 1756, F.R.S. 1745. Patricia Fara, “Knight, Gowin,” DNB, new ed. 31: 902–4. Wilson later painted Knight’s portrait.
- 9.
Sir George Savile, 1726–84, M.P. for Yorkshire 1759, F.R.S. 1747; Michell’s lifelong friend and patron of his living at Thornhill in Yorkshire from 1767. John Cannon, “Savile, Sir George,” DNB, new ed. 49: 107–9. Wilson painted Savile’s portrait twice; one portrait is reproduced, ibid., 107.
- 10.
Wilson, then living in London, came originally from Leeds.
- 11.
Wilson’s house was in Great Queen Street, Lincoln’s Inn Fields, London.
- 12.
Theophilus Lindsey, 1723–1808, minister of the Church of England at the time of this letter. Michell and Lindsey probably knew each other from Cambridge University, Lindsey having entered St. John’s College in 1741, the year before Michell entered Queens’. After having tutored the future duke of Northumberland, in 1753 Lindsey was presented to the valuable rectory of Kirby Wiske, Yorkshire, by the pupil’s father, the preferment mentioned in this letter. Through the Feathers Tavern Petition, which called for an end to the clergy’s obligatory subscription to the Thirty-nine Articles of the Church of England, he became Joseph Priestley’s closest personal friend. With the rejection of the petition, Lindsey left the Church of England, to found the first openly unitarian chapel, in London. Albert Nicholson, rev. G. M. Ditchfield, “Lindsey, Theophilus,” DNB, new ed. 33: 908–10. Joseph Priestley, A Scientific Autobiography of Joseph Priestley (1733–1804): Selected Scientific Correspondence, ed. R.E. Schofield (Cambridge, MA, and London: The MIT Press, 1966), 364; hereafter cited as Priestley, Autobiography.
- 13.
John Smeaton, 1724–92, civil engineer, instrument-maker, F.R.S. 1753. A.W. Skempton, “Smeaton, John,” DNB, new ed. 50: 981–85. Michell’s exact contemporary, Smeaton was born at Austhorpe Lodge, near Leeds. He went to London to study law, his father’s profession, where he met Benjamin Wilson, who likewise had come to London from Leeds to study law. Three years Smeaton’s senior, Wilson, who was then experimenting in electricity, probably introduced Smeaton to Gowin Knight and other fellows of the Royal Society, and perhaps to Michell as well. Trevor Turner and A. W. Skempton, “John Smeaton,” John Smeaton, F.R.S., ed. A.W. Skempton (London: Telford, 1981), 7–34, on 8. Michell’s letter refers to Smeaton’s work in Scotland. In 1754, the year of the letter, Smeaton wrote a report, which has not survived, on draining a large area of peat known as Lochmar moss, near Dumfries, “Lochar Moss Drainage”; this was the first of a number of projects he undertook in Scotland. A.W. Skempton, “Papers, Reports and Drawings,” ibid., 229–45, on 243.
- 14.
Daniel Wray, 1701–83, Cambridge and London antiquary, F.R.S. 1728/29. E.I. Carlyle, rev. J.A. Marchand, “Wray, Daniel,” DNB, new ed. 60: 402–3.
- 15.
Add Mss 4314: 539–41.
- 16.
Michell probably refers to the British Museum. The Museum was founded by an act of Parliament in 1753, to house Sir Hans Sloane’s natural history and antiquities collections and his library, to which the Cottonian and Harleian manuscripts were added. Two months before this letter, on 18 March 1758, the three collections were officially given departmental names, one of which was the Department of Natural History and Artificial Productions. James Empson, who had been in charge of Sloane’s Museum at Chelsea during Sloane’s lifetime, and who had continued to take care of it since 1753, became the under-librarian in charge of this department, which position he held until his death in 1765. Empson was not knowledgeable in natural history, and the principal librarian Gowin Knight took charge of its arrangements, presenting a plan for the “general distribution” of Sloane’s collection the year before this letter. Edward Miller, That Noble Cabinet: A History of the British Museum (Athens: Ohio University Press, 1974), 42–43, 60–61. A.E. Gunther, The Founders of Science at the British Museum, 1753–1900 (Suffolk: Halesworth Press, 1980), 14, 174. The British Museum opened to the public in 1759, the year after this letter. In 1765, Wray was appointed a trustee of the Museum.
- 17.
John Gordon, 1724–93, of Peterhouse and Emmanuel Colleges, graduated from Cambridge University in the same year as Michell. He was probably the John Gordon who officiated as Michell’s curate in the parish of St. Botolph, Cambridge. Entries 1 August and 11 October 1761, St. Botolph parish registers, Cambridge County Record Office. Gordon was a fellow of Emanuel College when Michell wrote this letter on his behalf, in vain as it turned out. He became a fellow of the Society of Antiquaries but not of the Royal Society, and in general his career did not take a scientific direction. He received a doctorate in divinity in 1765, in which year he was appointed chaplain to the bishop of Lincoln, followed by a series of preferments stopping short of bishop. Horace Walpole, Horace Walpole’s Correspondence, 48 vols., ed. W. S. Lewis (New Haven, CT: Yale University Press, 1937–83) 1: 281n.1. Alumni Cantabrigiensis 1, 2: 240.
- 18.
Francis Wollaston, 1731–1815, clergyman, astronomer, F.R.S. 1769; he and Michell had been students at Cambridge University at the same time and were good friends. J.D. North, “Wollaston, Francis,” DSB 14: 484–86.
- 19.
Probably Gowin Knight. See Letter 2.
- 20.
Charles Mason. See Letter 1.
- 21.
Birmingham manufacturer and engineer, F.R.S. 1785. Jennifer Tann, “Boulton, Matthew,” DNB new ed. 6: 805–10.
- 22.
MBP 244/248. This letter of introduction, carried by Benjamin Franklin on a visit to Birmingham, is published in part in Robert E. Schofield, The Lunar Society of Birmingham: A Social History of Provincial Science and Industry in Eighteenth-Century England (Oxford: Clarendon Press, 1963), 24.
- 23.
Benjamin Franklin, 1706–90, statesman, inventor, natural philosopher, F.R.S. 1756. Franklin was renowned for his electrical researches.
- 24.
Franklin had arrived in England the previous year as representative of the Pennsylvania Assembly. I.B. Cohen, “Franklin, Benjamin,” DSB 5: 129–39.
- 25.
Franklin met Boulton on this visit and performed an electrical experiment with him. Editorial note 7, Benjamin Franklin, The Papers of Benjamin Franklin, ed. L. W. Labaree (through vol. 14), W. R. Wilcox (through vol. 26), C. A. Lopez (vol. 27), and B. B. Oberg (from vol. 28) (New Haven and London: Yale University Press, 1959–) 9: 231.
- 26.
John Baskerville, 1706–75, Birmingham printer, had the year before published an edition of Virgil using a new type for which he would become well known. Listed in this edition as having bought six copies, the fellow printer Franklin met Baskerville on this visit to Birmingham, and they corresponded afterwards. “Baskerville, John,” DNB 1: 1281–88. Editorial note 4, Franklin, Papers 8: 53. Benjamin Franklin to Lord Kames, 27 September 1760, ibid., 9: 231, note 7. F.E. Pardoe, John Baskerville of Birmingham, Letter-Founder and Printer (London: Frederick Muller, 1975), 56–58.
- 27.
Sir John Pringle, 1707–82, physician, fellow 1745 and president 1772–78 of the Royal Society. Samuel X. Radbill, “Pringle, John,” DSB 11: 147–48.
- 28.
On 26 November 1758, a remarkable meteor was observed in various places in England and Scotland. The Royal Society heard a report on it, and subsequently Pringle solicited further information about it from friends. Extracts from letters Pringle received were read at a meeting of the Royal Society on 8 February 1759, and published in the Philosophical Transactions; two of the letters were from Michell. 8 Feb. 1759, Journal Book, Royal Society, 23: 253–554.
- 29.
Extract of a letter by Michell, quoted in Sir John Pringle, “Several Accounts of the Fiery Meteor, Which Appeared on Sunday the 26th of November, 1758, between Eight and Nine at Night,” Philosophical Transactions 51 (1759): 218–59, on 223–25; hereafter cited as PT. Pringle followed the paper with an analysis of the survey, “Some Remarks upon the Several Accounts of the Fiery Meteor (Which Appeared on Sunday 26th of November, 1758), and upon Other Such Bodies,” PT 51 (1759): 259–74. Pringle’s object was to determine the shape, size, height, and velocity of this particular meteor, but he also considered hypotheses about the nature of fiery meteors in general. From the descriptions, Pringle made drawings of the meteor, and in several places in Michell’s letter, he referred to them; his interpolations are given in square brackets, and the drawings are reproduced.
- 30.
Michell refers to figures 1 and 2 from Pringle, “Several Accounts of the Fiery Meteor,” 223.
- 31.
Pringle shared Michell’s doubt about the sound of the meteor: it was a “deception of that kind, which frequently connects sound with motion; and is the case of those who fancy they hear something when they see the shootings of the aurora borealis. “Any actual sound would have been heard minutes after the meteor had passed. The meteor was big, a mile and a half around, it seemed, as bright as the moon or even the sun, and short-lived, crossing the sky with a speed over a hundred times that of a cannon ball before it broke up and exploded. Pringle granted that if he had seen it, he himself might have been deceived. The variety and contradictions of the observations arose from an understandable “deception of the senses.” Pringle, “Some Remarks,” 259, 263, 265.
- 32.
This extract and paraphrase from a second letter by Michell appears in a footnote in Pringle, “Several Accounts,” 223.
- 33.
D/EHY 047.
- 34.
Savile was elected M.P. in a bye-election held in the previous month. From this time to the end of his career, he represented Yorkshire in the House of Commons.
- 35.
Arch bridges were a subject of interest around this time in Britain. Westminster Bridge, built of Portland and Burbeck stone, with thirteen large semi-circular arches and two small arches, was completed in 1750, the first bridge across the river Thames since London Bridge in the twelfth century. A monument to both architecture and engineering, this bridge was the start of England’s reputation for building excellent bridges. In 1759, the year of Mitchell’s letter, the two central arches of London Bridge were replaced by a single large arch.
- 36.
It is to be supposed that this weight is laid on in the same proportions with the parts of the Arch. [Michell]
- 37.
Portland stone, mined in southern Dorset.
- 38.
Limestone quarries in southern Dorset produce the so-called Purbeck marble.
- 39.
“Moor-stone,” the Cornwall name for a freestone found on moors, a granite or gritstone. William Joscelyn Arkell and S.I. Tomkeiff, English Rock Terms Chiefly Used by Miners and Quarrymen (London, New Toronto: Oxford University Press, 1953), 77.
- 40.
Everyone is familiar with granite and marble. Technically, granite is a crystalline igneous rock consisting of quartz and feldspar, and marble is recrystallized limestone or dolomite.
- 41.
Rag or ragstone, a hard, ragged stone.
- 42.
Slate, a rock made from clay, silt, or mud, with a laminate structure.
- 43.
This strength is greater than what is said to be the strength of Oak (if we take the slate & Oak bulk for bulk) in the proportion of about five to four; but if we take them weight for weight it is somewhat less than half the strength of the Oak. [Michell]
- 44.
Michell, as usual, does not explain his method. He evidently equates the bending moment on the beam with the resistance moment, and from the experiment with a load laid on the beam he determines the limiting resistance moment for a fracture, 182 foot-pounds (neglecting the insignificant moment due to the weight of the slender beam, 1 foot in length). To deduce the maximum length of a beam of the same cross-section bearing no applied load, he equates the maximum resistance moment to the bending moment due to the weight of the beam; the length comes out δA (L/2)2/2, where δ is the density of the stone, A is the area of cross section, and L is the length of the beam. From the measures Michell gives, the length of a beam that fractures under its own weight comes out about 11 feet.
- 45.
This form in an arch of so large a span in proportion to it’s height differs hardly sensibly from an arch of a circle, to which the top of the Arch is a Tangent. [Michell]
- 46.
The piece of Portland stone, which I tried, has stood vertically in it’s natural bed, & therefore we might very well expect it should not be of equal strength through out; Stone however ought always to be laid in the [same] situation that it had in it’s original bed, if we would have it preserve it’s greatest strength. [Michell]
- 47.
The arch principle uses wedge-shaped stones positioned radially on the inner face of the arch. In addition to their downward thrust, the wedges thrust outward, requiring a strong buttress to provide counter-thrust at the base of the arch. Michell’s design is a variant of the corbel arch, known as a false arch, since it does not use the arch principle; it does not require a strong buttress. The corbel arch is formed of projecting horizontal stones secured in place by masonry and, in Michell’s design, also by a wedge-like shape given to the end of the stone.
- 48.
Michell’s rectangular stones, his alternative to the wedge-shaped stones for holding the structure together and giving it strength, require a strong mortar to resist shear. In the year of this letter, his friend the civil engineer John Smeaton (see Letter 2) completed the structure that made him famous, the Eddystone Lighthouse. For this purpose Smeaton used an improved mortar. Together with William Cookworthy, a pioneer in the manufacture of English porcelain, he experimented with mixes of limestone and volcanic ash, producing a stone-hard, rapid-setting, water-resistant mortar, essential to the success of the lighthouse, and a forerunner of modern concrete mixes. The timing and the personal connection suggest one possible reason for Michell’s reappraisal of arch-bridge construction.
- 49.
Beginning here and extending to the end of this paragraph, a large, ragged piece is torn from the page.
- 50.
The piece is also torn out of the next page, removing most of the rest of the letter.
- 51.
This is the stone-arch bridge to cross the River Taff at Pontypridd in southern Wales. It was built by William Edwards, a contractor, and it took him three tries. He built his first bridge in 1743, with three arches. When after two years it washed away in a flood, he replaced it with a bridge with a single, slender, semi-circular arch. When the timber parts of this bridge washed away, he built his third bridge, which still stands. This bridge was completed in 1755, only four years before this letter. The bridge spans 140 feet, making it the largest single-span bridge in Britain at the time. With the shape of a circular segment, the bridge was impractical, too steep for horses and carts, but it was and is a beautiful bridge to behold. The problem with the Pontypridd Bridge was common with bridges of that kind, the weight of the buttresses pushing out the keystone, causing the bridge to collapse; Michell refers to this cause in the letter. T.G. Hughes, “William Edwards Bridge, Pontypridd, UK,” Proceedings of the Institution of Civil Engineers: Bridge Engineering 158(2) (June 2005): 71–80.
- 52.
Richard Lumley-Saunderson, 4th Earl of Scarborough, 1725–82, educated at Cambridge University, Whig, Deputy Earl Marshal 1765–77. In 1752 he married Savile’s youngest sister, Barbara or Arabella. Burke’s Peerage and Baronetage, 106th ed., ed. C. Mosley, 2 vols. (Crans, Switzerland: Burke’s Peerage, 1999) 2: 2560.
- 53.
Savile’s brother-in-law, married to his oldest sister.
- 54.
DD/SR, 219/3/5.
- 55.
Professorship of astronomy and geometry in Cambridge.
- 56.
William Talbot, first Earl Talbot, 1710–82, politician. George Edward Cokayne, The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, vol. 5 (Gloucester: Alan Sutton, 1982), 621.
- 57.
Robert Henley, first earl of Northington, 1708–72, jurist and politician. Peter D. G. Thomas, “Henley, Robert, First Earl of Northington,” DNB, new ed. 26: 360–63.
- 58.
Augustus Henry Grafton, Third Duke of Grafton, 1735–1811, politician. J.M. Rigg and Matthew Kilburn, “Grafton, Augustus Henry, Third Duke of Grafton,” DNB new ed. 19: 924–30.
- 59.
William Pitt, 1759–1806, politician. J.P.W. Ehrman and Anthony Smith, “Pitt, William,” DNB, new ed. 44: 470–97.
- 60.
Charles Pratt, first Earl Camden, 1714–94, lawyer and politician. Peter D.G. Thomas, “Pratt, Charles, First Earl Camden,” DNB, new ed. 45: 211–15.
- 61.
Roger Long, master of Pembroke College, appointed first Lowndean Professor in 1750, lived another four years after this letter. “Long, Roger,” DNB 6: 235–36.
- 62.
Richard Sharp, “Drummond, Robert Hay,” DNB, new ed. 16: 978–80.
- 63.
BpC&Pvii/472.
- 64.
Beneath the date in another’s handwriting, “Mr Michell.”
- 65.
John Thomas, 1696–1781, bishop of Winchester 1761; he presented Michell to the livings of Compton and Havant in 1763 and 1765, respectively. W.R. Ward, “Thomas, John,” DNB, new ed. 54: 346.
- 66.
Michell was ordained deacon on this date at York.
- 67.
Michell was ordained priest on this date at Ely.
- 68.
BpC&Pvii/472.
- 69.
DDFJ 11/1/7/249.
- 70.
We do not have the letter of 3 August 1772 or any other letters from Savile to Michell.
- 71.
This was probably Francis Maseres, 1731–1824, lawyer, reformer, writer on politics, economics, and history, from 1773 cursitor baron of the exchequer, and accomplished mathematician, F.R.S. 1771. He entered Cambridge University the same year Michell graduated, and like Michell he placed fourth wrangler in the mathematical tripos examination. Given their common interest in mathematics, Maseres and Michell probably knew one another from Cambridge. Maseres took an interest in Michell’s scientific work: John Hadley asked Thomas Birch to take Maseres as a guest to hear the reading of Michell’s paper on earthquakes at the Royal Society on 13 March 1760. British Library, Add. Mss. 4309, f.3. Like Michell and Savile, Maseres was a staunch Whig, and like Savile he was an advocate of church reform; in 1775, he presented a petition from Quebec Protestants to the Rockingham Whigs, which Savile presented to the House of Commons. At the time of this letter, he had just published a paper advocating life annuities in parishes, arguing that his proposal was needed because the poor failed to make provision during their working lives: “A Proposal for Establishing Life Annuities in Parishes for the Benefit of the Industrious Poor.” This proposal, a likely reason for his visit to Thornhill, was passed by the House of Commons but was rejected by the House of Lords. “Maseres, Francis,” DNB 12: 1292–94. Francis J. Gray, “The Parliamentary Career of Sir George Savile, Bart., 1759–1783” (Ph.D. diss., Fordham University, 1958), 132. Archibald Geikie, Annals of the Royal Society Club: The Record of a London Dining-Club in the Eighteenth and Nineteenth Centuries (London: Macmillan, 1917), 113.
- 72.
Rufford Abbey in Nottinghamshire was the Savile family seat.
- 73.
Sailing was one of Savile’s favorite pastimes.
- 74.
This was probably Henry Elmsal, 1750–97, Anglican minister, formerly a fellow of Emanuel College, Cambridge when Michell was a fellow of Queens’. In the year of this letter, Elmsal returned to his home county, Yorkshire, as a threefold pluralist: incumbent of East Ardsley, vicar of Batley, and rector of Emley. A prominent family in Thornhill from the sixteenth century, the Elmsals, or Elmsalls, owned property bordering on Michell’s church property. Like Michell, the family had a close connection with the Saviles. Henry Elmsal, father of the above, was rector of Thornhill, 1732–59. This Elmsal presented to the Royal Society the legacy of fifty pounds left to it by his patron Sir George Savile, 7th Bart., F.R.S. 1721, at his death in 1743. “Elmsal, Henry,” father and son, Alumni Cantabrigiensis 1, 2: 99–100. Barbara H. Nuttall, A History of Thornhill; And a Guide to the Church of St. Michael and All Angels (Huddersfield: Kirklees Cultural Services and Thornhill Church Council, 1995), 17, 54. 9 February 1743/44, Journal Book, Royal Society 18: 201.
- 75.
Beginning in 1766, William Gossip began soliciting support and subscriptions from influential persons to build a bridge at Thorp Arch across the River Wharf, north of Leeds. The purpose of the bridge was to free “gentlemen of the chase” from having to cross fords in pursuit of their quarry, for during floods the river was dangerous. Plans for the bridge were drawn by John Gott; see next note. The stone-arch bridge was completed in the year of this letter, 1772. David Cummings, Thorp Arch: The History of a Township (Thorp Arch: Thorp Arch Village Society, 1999), 92, 96.
- 76.
Hebton Bridge.
- 77.
John Gott, 1720–93, of Woodall near Bradford, surveyor of bridges for the West Riding of Yorkshire, resident engineer on the Aire and Calder Navigation canal. Gott was known as a designer and builder of arch bridges. Turner and Skempton, “Smeaton,” 25.
- 78.
In 1741 an iron foundry was started behind the cottage of Samuel Walker, 1715–82, in Grenocide, a village near Sheffield. Relocated in Rotherham in 1746, the foundry was operated by Samuel together with his brothers Jonathan, 1711–78, and Aaron, 1718–77. The Walkers became the most famous ironmasters in northern England. Cannon were their main production, but they also produced “almost all other cast iron articles, bar, sheet, slit, or rod iron, tinplate, steel of every sort and many articles of wrought iron.” Arthur Henry John, Minutes Relating to Messrs. Samuel Walker & Co., Rotherham, Iron Founders and Steel Refiners, 1741–1829, and Messers. Walkers, Parker & Co., Lead Manufacturers, 1788–1893 (London: Council for the Preservation of Business Archives, 1951), i–iii.
- 79.
Axles, or axle-trees, in the eighteenth century were usually made of wood, and the naves, the holes in the wheels into which the axles fit, were also made of wood, but sometimes axles were fitted with iron wearing plates, and the naves had iron bushes, that is, iron linings in the axle holes of the wheels. Michell describes “Iron axle trees,” bolted to wooden axles, made in Rotherham. A. Wolf, A History of Science, Technology, and Philosophy in the 18th Century, 2 vols., 2nd ed., ed. D. McKie (New York: Harper & Bros., 1961) 2: 553.
- 80.
The Bradford-Barnsley Turnpike was not constructed, according to a map of turnpike roads in 1841. R.C.N. Thornes, West Yorkshire: “A Noble Scene of Industry”: The Development of the County 1500 to 1830 (Wakefield: West Yorkshire Archeological Service, 1987), 43.
- 81.
Smallpox had replaced the plague as the main epidemic disease, and between epidemics it continued to take a toll. Inoculations for smallpox began to be performed in England in the 1720s. They were controversial at first, but by the middle of the century they were widely believed to lower mortality rates. Children were particularly vulnerable to the disease, and aristocratic parents such as Lord Scarborough took great interest in the procedure, despite its risks, for the survival of the title depended on the survival of the children. William G. Rothstein, Public Health and the Risk Factor: A History of an Uneven Medical Revolution (Rochester: Rochester University Press, 2003), 15–17.
- 82.
Gilbert Michell, 1726–92.
- 83.
Mary Michell, 1727/28–92.
- 84.
Ann Michell, formerly Brecknock, 1736–1818.
- 85.
William Watson, 1744–1824, Bath physician and naturalist, F.R.S. 1767. Included in his father’s biography: Simon Schaffer, “Watson, Sir William,” DNB, new ed. 57: 677–80, on 679–80.
- 86.
This date is Michell’s. At the top of the letter in someone else’s hand is the date 21 Jan. 1781.
- 87.
Royal Astronomical Society, Herschel MSS, W 1/13, M.99. The beginning of this letter is published in The Scientific Papers of Sir William Herschel … , 2 vols., ed. J.L.E. Dreyer (London: Royal Society and Royal Astronomical Society, 1912) 1:xxxi–xxxii. The middle part of the letter is published in A.J. Turner, Science and Music in Bath: An Exhibition in the Holburne of Menstrie Museum, Bath 22 September 1977–29 December 1977 (Bath: University of Bath, 1977), 96–98.
- 88.
We do not have Watson’s letter to Michell, initiating this exchange.
- 89.
William Herschel, 1738–1822, originally German, a musician by profession and an astronomer by predilection, F.R.S. 1781. M.A. Hoskin, “Herschel, William,” DSB 6: 328–36. Herschel lived in Bath at the time of this letter. Michell, who had not yet been introduced to him, communicated with him indirectly through their common acquaintance in Bath, Dr. William Watson. Watson delivered this and Michell’s next letter to Herschel, who kept them with his own correspondence. Dispensing with the go-between, Michell addressed his third letter directly to Herschel, Letter 14.
- 90.
What Herschel had “done” was build powerful telescopes. What he had “seen” with his telescopes was only then beginning to be known, with Watson’s help. Up to then, Herschel had reported his astronomical observations to the Bath Philosophical Society, to which Watson had introduced him. He had also begun to send papers to the Royal Society of London, the first of which dealt with a periodical star, the second with the height of the mountains of the moon; in both papers, he called attention to the remarkable capabilities of his telescope. In the first paper, he wrote that he magnified the star as much as 449 times, finding it “very full and round in the telescope,” and in the second paper “that for distinctness of vision this instrument [a Newtonian reflector of 6′ 8′′ focal length] is perhaps equal to any ever made.” From this time on, Herschel’s telescopes and the claims he made for their magnification and their distinct images greatly interested British astronomers, Michell among them. William Herschel, “Astronomical Observations on the Periodical Star in Collo Ceti,” PT 70 (1780): 338–44, on 342; “Astronomical Observations Relating to the Mountains of the Moon,” PT 70 (1780): 507–26, on 514. William Watson to William Herschel, 5 June 1780, Royal Astronomical Society, Herschel MSS, W 1/13 W.7 and M.13.
- 91.
A telescope of Newton’s design, from around 1668. Light from a primary spherically concave mirror is reflected by a plane mirror to the side of the telescope tube where it is received by the observer. As Michell explains, to obtain a distinct image at the focus, the primary mirror of a reflecting telescope should have the form of a conic section such as a parabola, and a circle is not a conic section, and so ideally a Newtonian mirror should not be spherical but parabolic, as Herschel’s was.
- 92.
By their method of working, instrument-makers gave their concave mirrors what is now called a “turned-down edge.” Newton, for example, gave one to the spherical mirror of his reflecting telescope. Henry C. King, The History of the Telescope (Cambridge, MA: Sky Publishing Corporation, 1955), 75.
- 93.
James Short, 1710–68, optical instrument-maker, astronomer, F.R.S. 1737. G. L’E. Turner, “Short, James,” DSB 12: 413–14.
- 94.
The plan of this telescope was published by James Gregory in 1663. A parabolic primary mirror reflects light to a focus; beyond the focus, a secondary concave mirror reflects it back through a hole in the first mirror to a secondary focus, and from there to the eyepiece, a plano-convex lens. D.T. Whiteside, “Gregory (more correctly Gregorie), James,” DSB 5: 524–30, on 525.
- 95.
Similar to Gregory’s, this telescope was designed by Laurent Cassegrain, and reported on in 1672. A convex secondary mirror reflects light from the primary mirror before it arrives at the focus, directing it back through a hole in the first mirror to the eyepiece. Spherical aberrations produced by the two mirrors partially cancel one another. Victor E. Thoren, “Cassegrain,” DSB 3: 97–98.
- 96.
Herschel erected his new twenty-foot telescope in the garden at New King Street in Bath that spring. Turner, Science and Music, 96.
- 97.
Herschel said that the Earth’s diurnal rotation was the one motion of the solar system that had not been studied closely. The reason it had not was that it was taken to be the standard against which the uniformity of other motions was compared. To decide if the Earth’s rotation is uniform, he compared it with Mar’s, once using the Earth’s rotation as the standard and then using Mar’s. “Astronomical Observations on the Rotation of the Planets Round Their Axes, Made with a View to Determine Whether the Earth’s (Diurnal) Motion Is Perfectly Equable,” PT 71 (1781): 115–38.
- 98.
Correct, as it turned out. In the first half of the twentieth century, a disparity between observations of the motion of the Moon and lunar theory was determined to be an irregularity in the rotation of the Earth on its axis. This led to the introduction of “ephemeris” time, which is independent of the rotation and is based instead on the motions of the Moon and the Earth. “Celestial Mechanics,” Encyclopaedia Britannica 5: 93–95, on 93.
- 99.
Lunar tables drawn up by the Göttingen astronomer Johann Tobias Mayer, 1723–62. Eric G. Forbes, “Mayer, Johann Tobias,” DSB 9: 232–35.
- 100.
Royal Astronomical Society, Herschel MSS, W 1/13, M.100. The first half of this letter is published in Turner, Science and Music, 98.
- 101.
The dashes standing for a curse word; Michell strongly opposed Britain’s war with the American colonies. See Letter 15.
- 102.
Joseph Priestley, 1733–1804, chemist, natural philosopher, Dissenting minister and theologian, F.R.S. 1776. Robert E. Schofield, “Priestley, Joseph,” DSB 11: 39–47.
- 103.
Herschel MSS, W 1/13, M.101. This letter is published in Turner, Science and Music, 98–102.
- 104.
Herschel’s letters of 3 and 8 March are missing. The first of these evidently was a response to Michell’s indirect letter of 23 February, which introduced the subject of “distinctness” of images, Letter 13.
- 105.
Christiaan Huygens, 1629–95, Dutch physicist, mathematician, and instrument-maker. H.J.M. Bos, “Huygens, Christiaan,” DSB 6: 597–613.
- 106.
Robert Smith, 1689–1768, Plumian Professor of Astronomy and Experimental Philosophy in Cambridge University, F.R.S. 1718, author of A Compleat System of Opticks in Four Books, viz. A Popular, a Mathematical, a Mechanical, and a Philosophical Treatise. To Which Are Added Remarks upon the Whole, 2 vols. (Cambridge, 1738). Edgar W. Morse, “Smith, Robert,” DSB 12: 477–78.
- 107.
For his book The History and Present State of Discoveries Relating to Vision, Light, and Colours, 2 vols. (London, 1772), Priestley asked Michell for an account of the “indistinctness of vision” occasioned by very small pencils of light. On the pages cited in this letter, Priestley describes Michell’s demonstration of indistinctness. With a candle or the Sun as the source of light and a telescope with a small aperture for producing small pencils of rays, Michell viewed the rays through a sheet of cardboard pierced with small circular and triangular holes. When the pencil was 1/1,000th part of an inch, he was unable to “distinguish a small triangular hole from a circular one,” and when it was 1/100th part of an inch, he found the image “pretty indistinct.” He suspected that indistinctness begins with a pencil as large as 1/30th part of an inch. Ibid., 785–86.
- 108.
By Priestley’s account, Michell found that in grinding mirrors and lenses, all concave spherical surfaces tend toward a parabolic or hyperbolic form. Ibid., 799–800.
- 109.
Two years before this letter, the instrument-maker Jesse Ramsden, PT 69 (1779): 419–25, showed that the aberrations of the main and secondary mirrors of a Cassegrain telescope tend to cancel one another, whereas in the Gregorian telescope the two aberrations are additive. King, Telescope, 75.
- 110.
Father Noël, a Bernardin priest, was custodian of Louis XV’s collection of scientific instruments. In 1761 he completed a 22-foot reflecting telescope with a mirror 23½ inches in diameter. It performed poorly, and a few years later he refigured the mirrors, but it apparently still performed poorly. King, Telescope, 91.
- 111.
Watson’s two letters to Michell, no doubt his replies to Michell’s of 22 January and 23 February 1781, are missing.
- 112.
Still called a comet, this was, in fact, the first new planet discovered since antiquity, Uranus. Herschel first observed it two months earlier, on 13 March 1781. Five days later he showed it to William Watson, and soon news of the sighting reached the Greenwich and Oxford Observatories and interested persons such as Michell. In a letter to Watson on 4 April, Maskelyne suggested that the object might be a planet, evidently the first to do so; proof would come later, and from abroad. Derek Howse, Nevil Maskelyne: The Seaman’s Astronomer (Cambridge: Cambridge University Press, 1989), 147.
- 113.
DD/SR 221/93.
- 114.
Charles Watson-Wentworth, Lord Rockingham, 1730–82, Whig leader. “Rockingham, 2d Marquis of,” Webster’s Biographical Dictionary (Springfield: G. & C. Merriam, 1970), 1271. Because of the American War, Lord North’s ministry lost support, and in March 1782 the Rockingham Whigs came to power. Savile belonged to this faction. Rockingham died in July, the occasion of this letter.
- 115.
When Rockingham died, the king appointed William Petty, Lord Shelburne head of the treasury, with Frederick, Lord North still regarded as leader. Charles James Fox, Edmund Burke, and other Rockingham Whigs resigned over their differences with Shelburne on America. At the end of 1782, the king accepted American independence, and early the next year peace was made.
- 116.
Never robust, Savile was seriously ill at the time of this letter. In 1782 he still attended sessions of Parliament, but he rarely spoke. In 1783 he announced his resignation to his constituents, and the next year he died.
- 117.
DD/FJ/11/1/7/112/1.
- 118.
Probably Dr. Robert Amory, 1720–1805, who at the time of this letter had been practicing medicine in Wakefield for over twenty years. He is mentioned in Michell’s brother Gilbert’s will. His father was the religious author Thomas Amory, 1691?–1788, who also lived in Wakefield. Joseph Hirst Lupton, Wakefield Worthies; or, Biographical Sketches of Men of Note Connected … with … Wakefield in Yorkshire … (London, 1864), 165–66.
- 119.
Charles Stanhope, Lord-Viscount Mahon, 3d Earl Stanhope, 1753–1816, politician, inventor, electrician, F.R.S. 1772. “Stanhope, Charles,” DNB 18: 888–92. To prevent the public from being defrauded by false coiners and persons who clipped or otherwise diminished the weight of coins, Mahon had earlier proposed changes in the way gold coins were made and corresponding changes in the law: Considerations on the Means of Preventing Fraudulent Practices on the Gold Coin (London, 1775). These changes concerned milling, not alloying; for example, the date of the coin was to be sunk in, and the letters of the inscription were to be set near the edge of the coin. The new changes proposed by Lord Mahon, which Michell describes in the letter, concerned alloying. Ibid., 7, 9. Ghita Stanhope, The Life of Charles Third Earl Stanhope, rev. G.P. Gooch (London, New York, Bombay: Longmans, Green, 1914), 32.
- 120.
Bryan Higgins, 1737 or 1741–1818, London chemist. Arnold Thackray, “Higgins, Bryan,” DSB 6: 382–84.
- 121.
John Birch was appointed surgeon at St. Thomas’s Hospital in place of the deceased George Martin on 12 May 1784. His competition, Henry Cline, withdrew. F.G. Parsons, The History of St. Thomas’s Hospital, vol. 2: From 1600 to 1800 (London: Methuen, 1934), 244.
- 122.
John Michell’s brother, Gilbert, had been in partnership with Nathaniel Thomas, drysalter by trade, who was alderman for Walbrook, London, from 1773 until his death in 1781. Gilbert Michell’s obituary, Gentleman’s Magazine 62: 2 (1796), 1061. Letter from the City Archivist, 19 August 1999, Corporation of London Records Office.
- 123.
Sir George Armytage, 3d Bt., 1734–83, high sheriff of Yorkshire 1755, M.P. for Yorkshire 1761–68. He was a prominent member of the Thornhill Church, owning sixty-seven sittings, distributed among his tenants. Account of Thornhill sittings, 16 October 1778, Halifax Central Library, KMA 329/1 and 2. Burke’s Peerage and Baronetage, 106th ed., 2 vols., ed. C. Mosley (Crans, Switzerland: Burke’s Peerage, 1999), 1: 108.
- 124.
DD/FJ/11/1/7/112.
- 125.
Cavendish Scientific Manuscripts. This Letter is published in Christa Jungnickel and Russell McCormmach, Cavendish, the Experimental Life (Lewisburg: Bucknell University Press, 1999), 564–65. I thank the Trustees of the Chatsworth Settlement for permission to publish Henry Cavendish’s correspondence with John Michell.
- 126.
Lord Charles Cavendish, 1704–83, M.P. for several constituencies 1725–41, natural philosopher, F.R.S. 1727. Jungnickel and McCormmach, Part 1, “Lord Charles Cavendish,” Cavendish, the Experimental Life, 19–128.
- 127.
Michell had good reason to expect a favorable reading of this, his second and last paper on the stars. The two papers were closely related, and Cavendish was known to have formed a good opinion of the first, published in 1767. Of it, William Watson wrote to Herschel that he was “glad to find that you have lately examined Mr Michel’s paper, wch you may remember I first pointed out to your notice. I know that some of the closest & chastest reasoners I am acquainted with approve of it, such as Mr Henry Cavendish.” William Watson to William Herschel, 16 March 1783, Royal Astronomical Society, Herschel MSS, W 1/13, W.24.
- 128.
Michell’s paper would not be read until 27 November 1783, after the recess of the Royal Society: “On the Means of Discovering the Distance, Magnitude, &c. of the Fixed Stars, in Consequence of the Diminution of the Velocity of Their Light, In Case Such a Diminution Should Be Found to Take Place in Any of Them, and Such Other Data Should Be Procured from Observations, as Would Be Farther Necessary for That Purpose. By the Rev. John Michell, B.D.F.R.S. In a Letter to Henry Cavendish, Esq. F.R.S. and A.S.,” PT 74 (1784): 35–57.
- 129.
Set apart from other telescopes of the time by its size, Michell referred to it as the “great Telescope,” a wording Cavendish followed.
- 130.
Ever since becoming rector of Thornhill in Yorkshire in 1767, Michell made the long journey to London as often as circumstances permitted, which were not as often as he wished. In the year he began corresponding with Cavendish, 1783, Michell was fifty-nine and suffering from an unspecified illness, which he had contracted the previous year, making his travel plans uncertain. He had been to London recently, as he noted in the letter accompanying his paper, Letter 18. The next year, 1784, he visited London for at least a month and a half, as a guest attending every weekly dinner of the Royal Society Club between 6 May and 24 June. Royal Society Club, Minute Book, Royal Society, vol. 7.
- 131.
This letter to Henry Cavendish was printed at the beginning of Michell, “Means of Discovering the Distance,” 35–36; reprinted in Jungnickel and McCormmach, Cavendish, the Experimental Life, 566.
- 132.
The principle of Michell’s paper is Newton’s law of universal gravitation, as it applies to light, as he explains in the fourth paragraph of the paper: “Let us now suppose the particles of light to be attracted in the same manner as all other bodies with which we are acquainted; that is, by forces bearing the same proportion to their vis inertiae, of which there can be no reasonable doubt, gravitation being, as far as we know, or have any reason to believe, an universal law of nature.” It follows from this principle that stars attract the light they emit, and that sufficiently large stars retard the velocity of their light in detectable measure. The “method” of detection follows from Newton’s theory of refraction: the extent to which a ray of light is bent by a refracting body such as a glass prism depends on the velocity of the ray. Michell, “Means of Discovering the Distance,” 37.
- 133.
Michell’s calculation of the proportion that the force with which light is propelled from the Sun bears to the force of gravity is given in Priestley, Vision, Light, and Colours, 786–91. From the disproportion of the two forces, Priestley observes, on 789, “what an extremely little diminution the velocity of light can suffer by the attraction of the sun.”
- 134.
William Herschel, “Catalogue of Double Stars,” PT 72 (1782): 112–62.
- 135.
See previous Letter, note 5.
- 136.
Cavendish Scientific Manuscripts. This letter is published in Jungnickel and McCormmach, Cavendish, the Experimental Life, 567–69.
- 137.
Previous Letter.
- 138.
Sir Joseph Banks, 1743–1820, botanist, fellow in 1766 and president of the Royal Society from 1778 to the end of his life. George A. Foote, “Banks, Joseph,” DSB 1: 433–37.
- 139.
This probable reading of the passage omits a “the” and an “of.” Cavendish wrote, “The surest way of securing the merit of an invention to the author … ” He crossed out “an invention,” replacing it with “discovery,” which he also then crossed out.
- 140.
The Monday Club met on Mondays at the George and Vulture Tavern, located in George Yard, Lombard Street.
- 141.
Michell followed Cavendish’s advice. See Letters 20 and 21.
- 142.
This is the first mention of “weighing the world,” Michell’s experiment to determine the average density of the earth by means of a torsion balance. Michell built an apparatus for it, but he did not live to perform the experiment. After Michell’s death, Cavendish acquired the apparatus, rebuilt it in large part, and performed the experiment. “Experiments to Determine the Density of the Earth,” PT 88 (1798): 469–526, on 469.
- 143.
Here Cavendish tried three phrasings before he settled on a fourth: “I had rather hear,” “I think I had,” and another which is illegible because of the crossings out.
- 144.
John Goodricke, 1764–86, whose unfamiliar name was spelled a number of ways by Cavendish and Michell, was a young, deaf-mute astronomer living in York, who had just communicated his first paper to the Royal Society. Cavendish heard it read at the meeting of the Society on 15 May, less than two weeks before he wrote to Michell. This paper, for which Goodricke received the Copley Medal of the Society, was published later that year: “A Series of Observations on, and a Discovery of, the Period of the Variation of the Light of the Bright Star in the Head of Medusa, Called Algol,” PT 73 (1783): 474–92. Kopal Zdeněk, “Goodricke, John,” DSB 5: 467–69.
- 145.
Cavendish left a space after “was,” probably intending to add a number.
- 146.
Richard Kirwan, 1733?–1812, F.R.S. 1780, is best known for his work in chemistry, but he had broad interests in the physical sciences, which included astronomy. Born in Ireland, he was then living in London. E.L. Scott, “Kirwan, Richard,” DSB 7: 387–90.
- 147.
William Herschel, still a new name to Cavendish.
- 148.
Nevil Maskelyne, 1732–1811, astronomer royal, F.R.S. 1759. His annual Nautical Almanac and Astronomical Ephemeris together with tables and explanations was his “greatest monument” to astronomy. Eric G. Forbes, “Maskelyne, Nevil,” DSB 9: 162–64. Herschel found support for his belief that most stars have a proper motion in this publication: on 2 of the explanations of the tables, Maskelyne “mentions the ‘peculiar but small motions [of the stars], which many, IF NOT ALL OF THEM, have among themselves, which have been called their proper motions, the causes and laws of which are hid for the present in almost equal obscurity.’” Herschel, “On the Proper Motion of the Sun,” 260.
- 149.
Johann Tobias Mayer, 1723–62, German astronomer and cartographer. Eric G. Forbes, “Mayer, Johann Tobias,” DSB 9: 232–35. In his paper on the motion of the Sun, Herschel drew on an extract taken by J. J. L. de Lalande from the Göttingen astronomer Tobias Mayer’s tables of proper motions. Herschel added a postscript to his paper after Alexander Aubert gave him a copy of the “scarce edition” of Mayer’s original work, the posthumous Opera inedita Tobiae Mayeri (Göttingen, 1775), with its “extensive table” of proper motions. Herschel, “On the Proper Motion of the Sun,” 274.
- 150.
Drawing on evidence that certain stars had changed position, and inferring from the principle of attraction that all stars including the Sun must move, and for support citing Michell on the probable motion of the Sun, Herschel concluded that the observed proper motion of stars is in part an apparent motion owing to the motion of the Sun and its planets with respect to the stars. From the tables, he deduced that the Sun is moving in the direction of the constellation Hercules. “On the Proper Motion of the Sun,” 248, 260.
- 151.
Thomas Hutchins, 1730–89, Governor of Albany Fort, Hudson Bay.
- 152.
Thomas Hutchins, “Experiments for Ascertaining the Point of Mercurial Congelation,” PT 73 (1783): *303–*370.
- 153.
Readings with mercury thermometers of temperatures hundreds of degrees below zero had been reported. In the experiments Cavendish designed and Hutchins carried out at Hudson Bay, the bulb of a mercury thermometer was immersed in a mercury bath, and since mercury freezes from the outside in, the still-liquid mercury in the thermometer registered the temperature at which the bath began to harden around the edges: minus thirty-nine degrees Fahrenheit. The reason for the earlier erroneous, extremely low temperature readings was the shrinkage of the mercury in the thermometer at the temperature at which mercury freezes.
- 154.
Henry Cavendish, “Observations on Mr. Hutchins’s Experiments for Determining the Degree of Cold at Which Quicksilver Freezes,” PT 73 (1783): 303–28.
- 155.
Sir Charles Blagden, 1748–1820, physician, natural philosopher, fellow in 1772 and secretary of the Royal Society 1784–97. “Blagden, Sir Charles,” DNB 2: 617–18.
- 156.
Charles Blagden, “History of the Congelation of Quicksilver,” PT 73 (1783): 329–97.
- 157.
Using a freezing mixture, Cavendish froze mercury at his house in Hampstead on 26 February 1783, as Blagden recorded the next day. 27 February 1783, Charles Blagden Diary, Royal Society, 1.
- 158.
Cavendish Scientific Manuscripts. This letter is published in Jungnickel and McCormmach, Cavendish, the Experimental Life, 570–78.
- 159.
This letter is in reply to Cavendish’s draft letter of 27 May, Letter 19. Michell refers to it as the letter of 3 June. Between those two dates, Cavendish made additions to the draft letter, as we learn from Michell’s comments.
- 160.
Algol is, indeed, a double star of the kind Michell proposes: a small bright star orbits and partially eclipses a large faint star.
- 161.
5/8.5 or 0.58823; Michell uses a comma where we use a period.
- 162.
The alternative hypothesis for explaining the periodic variations in the brightness of stars was dark regions on the surface of spinning stars, analogous to sunspots. In his paper on Algol, Goodricke mentions this hypothesis together with that of eclipsing double stars.
- 163.
In that paper, Michell proposes a catalog of stars on a new plan, urging astronomers to “enquire into the exact quantity of light, which each star affords us separately, when compared with the Sun; that, instead of distributing them, as has hitherto been done, into a few ill defined classes, they may be ranked with precision both according to their respective brightness, and the exact degree of it.” “Probable Parallax,” 241.
- 164.
Edward Nairne, 1726–1806, London instrument-maker, F.R.S. 1776. E.G.R. Taylor, The Mathematical Practitioners of Hanoverian England 1714–1840 (Cambridge: Cambridge University Press, 1966), 214.
- 165.
Jean-Sylvain Bailly 1736–93, astronomer, member of the Royal Academy of Sciences, later mayor of Paris. Seymour L. Chapin, “Bailly, Jean-Sylvain,” DSB 1: 400–2.
- 166.
Following a study of the inequalities of the four known satellites of Jupiter, Bailly proposed a technique for measuring their light that involved placing graduated pasteboard diaphragms in front of the object glass of a telescope to intercept their light. Michell recognized that this method was not limited to the observation of Jupiter’s satellites, but was a general method for making precise comparisons of light intensities.
- 167.
Michell did not cite Bailly’s memoir of 1771 on the method of measuring light, published by the Academy of Sciences, but instead his “Letter to the Rev. Nevil Maskelyne, F.R.S. Astronomer Royal … Containing a Proposal of Some New Methods of Improving the Theory of Jupiter’s Satellites,” PT 63 (1773): 185–216.
- 168.
Pierre Bouguer, 1698–1758, member of the Paris Academy of Sciences, published a pioneering work on the comparison of light intensities, Essai d’optique sur la gradation de la lumière in 1729. A much enlarged version of this, his Traité, was published posthumously in 1760: Pierre Bouguer’s Optical Treatise on the Gradation of Light, translated with an introduction by W. E. Knowles Middleton (Toronto: University of Toronto Press, 1961). Bouguer is regarded as the inventor of the photometer, the progenitor of Michell’s astrophotometer. W.E. Knowles Middleton, “Bouguer, Pierre,” DSB 2: 343–44.
- 169.
Beginning in 1779, Herschel looked for double stars as a means of measuring the distance of stars. By assuming that the fainter member of a double star is sufficiently distant to be regarded as a fixed star, he hoped to determine the distance of the brighter, supposedly nearer star from its annual apparent motion with respect to the fixed star. He catalogued 269 double and multiple stars, 227 of which were recorded for the first time. After he had delivered his paper, he found that Mayer had discovered another 31 double stars. Herschel, “Catalogue of Double Stars,” 157–58. Hoskin, “Herschel,” 328–30.
- 170.
Letter 19.
- 171.
In his first paper on the stars, Michell writes that the observed apparent change in the position of stars “may be owing either to the real motion of the stars themselves, or to that of the Sun, or partly to the one, and partly to the other. As far as it is owing to the latter (which it is by no means improbable may in some measure be the case) it may be considered as a kind of secular parallax, which, if the annual parallax of a few of the stars should some time or other be discovered, and the quantity and direction of the Sun’s motion should be discovered likewise, might serve to inform us of the distances of many of them, which it would be utterly impossible to find out by any other means.” “Probable Parallax,” 252–53.
- 172.
William Watson wrote to Herschel, “I was extreamly sorry to hear by means of your Brother, that you have had the misfortune to break your best 12 Inch Speculum by the frost.” In his next letter, Watson added, “after so many hours Labour.” Watson to Herschel, 19 January and 16 March 1783, Herschel MSS, Royal Astronomical Society, W 1/13, W.23 and 24.
- 173.
Charles Blagden, 1748–1820, physician, F.R.S. 1772, secretary of the Royal Society 1784. David Philip Miller, “Blagden, Sir Charles,” DNB new ed. 6: 59–60.
- 174.
Hutchins’s experiments and Cavendish’s analysis of them were published side by side, with Blagden’s paper immediately following. Their three papers are cited above, Letter 19.
- 175.
The draft of this letter, Letter 19, makes no mention of Priestley’s experiments; Cavendish added this information to the final letter. Joseph Priestley, “Experiments Relating to Phlogiston, and the Seeming Conversion of Water into Air,” PT 73 (1783): 398–434.
- 176.
The Royal Society Club was commonly called the “Society.”
- 177.
The Cat and Bagpipes was a popular tavern and chop-house on the corner of Downing Street, next to King’s Street. Geikie, Michell, 58.
- 178.
Cavendish Scientific Manuscripts. This letter is published in Jungnickel and McCormmach, Cavendish, the Experimental Life, 570–78.
- 179.
Letter 20.
- 180.
Letter 22 is two sheets of corrections of Michell’s paper by Maskelyne, which Cavendish incorporates here.
- 181.
Two months later, Charles Blagden wrote to a colleague that astronomers were still unsuccessful in their efforts to detect a difference in the velocity of light coming from different stars, but that they intended to acquire instruments constructed for this purpose. Letter to Claude Louis Berthollet, 24 Oct. 1783, draft, Blagden Letterbook, Yale.
- 182.
Cavendish had a photometer made for him, perhaps on the plan of the one he describes to Michell in this letter. With it, he and Blagden observed Algol; Blagden reported to Banks that “whether it be that he [Goodricke] made the period too long, or that it is not absolutely uniform, cannot be determined. Mr Cavendish’s photometer is not found to answer.” Charles Blagden to Sir Joseph Banks, 16, 23, and 30 October 1783, Fitzwilliam Museum Library, Perceval H 190, H 193, H 195.
- 183.
William Parker, who with his sons John and Samuel operated a glass manufacturing firm in London, provided Priestley with “every instrument I wanted in glass,” including burning lenses. Taylor, Mathematical Practitioners of Hanoverian England, 294. Priestley, Autobiography, 367.
- 184.
Cavendish Scientific Manuscripts. This two-page list of corrections of Michell’s paper by Nevil Maskelyne is published in Jungnickel and McCormmach, Cavendish, the Experimental Life, 582. It is folded into the preceding draft letter from Cavendish to Michell, 12 August 1783. It is not, strictly speaking, a letter, and although it is written for Michell it was delivered to Cavendish. It is included in this collection of Michell’s letters for completeness.
- 185.
At the bottom of the second side, and upside down, is a calculation in Cavendish’s handwriting.
33
35,88
2,88 = 2.528
- 186.
Cavendish noted on this draft letter, “To Michell Nov. 4 1783.” Michell referred to this letter as Cavendish’s letter of 3 November; see Letter 24.
- 187.
Cavendish Scientific Manuscripts. This letter is published in Jungnickel and McCormmach, Cavendish, the Experimental Life, 583.
- 188.
Cavendish Scientific Manuscripts. This letter is published in Jungnickel and McCormmach, Cavendish, the Experimental Life, 584–85.
- 189.
Letter 23.
- 190.
The transcription here of Michell’s notation for seconds and sixtieths of seconds of arc includes a change from the original. Beneath the double and triple strokes, he wrote two dots, as he did after the decimal proportion of a second in 35″,88. These dots are omitted, and a period is added between the seconds and sixtieths of a second, corresponding to the way his numbers are set in his paper in the Philosophical Transactions. Thus, in place of 2″53‴ with two dots under the strokes, it reads 2″.53‴.
- 191.
The letter would have enclosed Maskelyne’s three-page printed directions for observers of meteors, dated 6 November, A Plan for Observing the Meteors Called Fire-Balls.
- 192.
Cavendish Scientific Manuscripts. This letter is published in Jungnickel and McCormmach, Cavendish, the Experimental Life, 587–91.
- 193.
Letter 21.
- 194.
Here Michell acknowledges a commonly held opinion that light and electricity, and usually also magnetism, heat, and phlogiston, are substances distinct from ordinary matter. These substances were often held to be weightless, “imponderable fluids.” Michell does not suggest that light is weightless, but he does allow that it and also the electric fluid might not respond to gravitation in the same measure as ordinary bodies. Cavendish would have regarded Michell’s caution as reasonable. Three years earlier, in October 1780, he performed an experiment to examine the same question about gaseous matter: “It was tried whether the vis inertia of phlogisticated air was the same in proport. to its weight as that of common air.” “Experiments on Air,” Cavendish Scientific Manuscripts, Devonshire Collections, Chatsworth, II, 5: 80–82. Newton experimented with pendulums made of different kinds of substances with the same question in mind. Newton, Michell, and Cavendish knew that there was no theoretical reason for the equality of inertial mass and gravitational mass in all forms of matter; for the time being, the relationship of the two masses was an experimental question.
- 195.
Michell, “Probable Parallax,” 250–54.
- 196.
There was considerable scientific interest in the Indian practice of cooling water by evaporation, an illustration of the newly acquired and imperfectly understood concept of latent heat. Upon witnessing the chemist John Hadley sink the mercury in a thermometer by dipping the bulb into ether and then letting the ether evaporate, Benjamin Franklin observed: “It is but within these few years, that the European philosophers seem to have known this power in nature, of cooling bodies by evaporation. But in the east they have long been acquainted with it.” Letter to John Lining, 17 June 1758, in Franklin, Papers 8: 109. In India it was commonly believed that water must be boiled to make ice, but one observer found that boiling was not done in Benares, where porous pans were used. John Lloyd Williams, “Account of the Method of Making Ice at Benares,” PT 83 (1793): 56–58. In 1776–77 Cavendish carried out experiments on the changes in temperature of boiled and unboiled water held in glazed and porous pans. “Evaporation,” Cavendish Scientific Manuscripts, Devonshire Collections, Chatsworth, III(a), 12.
- 197.
Antoine Baumé, 1728–1804, chemist, member of the Academy of Sciences. E. McDonald, “Baumé, Antoine,” DSB 1: 527.
- 198.
By September of the next year, Michell had made a daylight test, as Herschel learned from his friend William Watson: “Have you heard of the success of Mr Michel’s speculum? My father informed me about a fortnight ago, that Mr Dalrymple has paid him a visit, & saw the Telescope, & that it performs extreamly well upon day objects.” Letter of 8 September 1785, Herschel MSS, Royal Astronomical Society, W 1/13, W.38.
- 199.
Within three weeks, by 6 May, Michell was in London.
- 200.
Blagden Letterbook, 1783–1787, Osborn Shelves fc15.
- 201.
Barking and Dagenham are parts of London, located on the east side of the city, north of the River Thames.
- 202.
Thomas Hyde Page, 1746–1821, military engineer, F.R.S. 1783. “Page, Thomas Hyde,” DNB 15: 43–44.
- 203.
Any metallic-looking sulfides, the commonest of which is pyrite, from which they take their name; pyrite is iron disulfide, a brass-yellow mineral with a metallic luster.
- 204.
A principle or substance thought to exist in all combustible bodies. This letter was written on the eve of the Chemical Revolution, which rejected phlogiston.
- 205.
Any stone relating to or resembling iron.
- 206.
Any rock containing iron. Arkell and Tomkeiff, English Rock Terms, 63.
- 207.
A genus of polyps; sea-fan or sea-plume.
- 208.
William Herschel, “On the Construction of the Heavens,” PT 75 (1785): 213–66.
- 209.
Herschel, “On the Construction of the Heavens,” 255, cites Michell’s paper, “Probable Parallax.”
- 210.
With his new telescope, a Newtonian reflector of 20-foot focal length and 18.7-inch aperture, Herschel added 466 new star clusters and nebulas to his previous 103. “Account of Some Observations Tending to Investigate the Construction of the Heavens,” PT 74 (1784): 437–51.
- 211.
Because the light-gathering power of a telescope is as the square of the aperture, Michell’s telescope with an aperture of 29½ inches was over 2½ times Herschel’s.
- 212.
Joseph Priestley, “Experiments and Observations Relating to Air and Water,” PT 75 (1785): 279–309.
- 213.
William Morgan, 1750–1833, actuary, F.R.S. 1790. “Electrical Experiments Made in Order to Ascertain the Non-Conducting Power of a Perfect Vacuum, &c.,” PT 75 (1785): 272–78. D. L. Thomas, rev. Robin Pearson, “Morgan, William,” DNB, new ed., 39: 156–57.
- 214.
William Roy, 1726–90, military surveyor, founder of the Ordnance Survey, F.R.S. 1767. Elizabeth Baigent, “Roy, William,” DNB, new ed. 48: 50–53.
- 215.
Roy was in charge of the English half of the Anglo-French project to determine the relative locations of the Greenwich and Paris Observatories. The method was to lay triangles from London to Dover, there to connect with triangles laid on the French side. Roy selected Hownslow Heath for laying the 27,404-foot baseline for the triangles.With instruments built for the purpose, he measured the baseline three times, with a discrepancy of under three inches. For the accuracy with which he made this measurement, he received the Copley Medal of the Royal Society in 1785. William Roy, “An Account of the Measurement of a Base on Hounslow-Heath,” PT 75 (1785): 385–480.
- 216.
The Philosophical Transactions was Blagden’s responsibility as one of the secretaries of the Royal Society.
- 217.
Henry Cavendish, “Experiments on Air,” PT 75 (1785): 372–84.
- 218.
Nitrogen.
- 219.
Dephlogisticated air or oxygen.
- 220.
Correspondence column, Monthly Review 72 (1785): 478–80.
- 221.
We insert this letter, to oblige the Writer, though the Review hath little concern in the subject of it. [Monthly Reviewers.]
- 222.
In 1751, the “New Style” calendar was introduced; thereafter, the new year began on 1 January instead of on 25 March.
- 223.
John Canton, 1718–72, schoolmaster, natural philosopher, F.R.S. 1749. John L. Heilbron, “Canton, John,” DSB 3: 51–52.
- 224.
Andrew Kippis, “Canton (John),” Biographia Britannica … , 2d ed., ed. A. Kippis, vol. 3 (London, 1784), 215–22. Kippis obtained the material for the biography from Canton’s oldest son, William. Prefaced by a description of John Canton as a natural philosopher of “penetrating genius,” a shortened version of this biography, omitting a footnote about artificial magnets, was published in the Monthly Review 71 (November 1784): 321–28, on 321.
- 225.
Michell’s book was favorably reviewed and copiously quoted in Monthly Review, 2d ed., 2 (March 1750): 411–17. The anonymous reviewer was the apothecary William Bewley, who later helped Priestly with his electrical researches, and who at some point became friends with Michell.
- 226.
The biography states that Canton’s paper on magnets was read to the Royal Society at its meeting on 17 January 1750. Kippis, “Canton,” 216. That dating is correct according to the Old Style calendar, by which January 1750 comes late in the year; by the New Style, which was introduced in 1751, the date was 17 January 1751. In 1750, earlier than Canton’s reading on 17 January 1750/51, Michell published A Treatise of Artifcial Magnets; In Which Is Shewn an Easy and Expeditious Method of Making Them, Superior to the Best Natural Ones … (Cambridge, 1750).
- 227.
The certificate recommending Canton’s membership was read at the meeting of the Royal Society on 21 December 1749; Certificate Book, Royal Society.
- 228.
At the meeting, Martin Folkes, president of the Royal Society, read a paper about Canton’s experiments “impregnating steel bars with magnetism,” which he had witnessed at Canton’s home. Canton then demonstrated the principal experiment reported in Folkes’s paper, after which his own paper containing his method was read. Journal Book, Royal Society, 20: 420–24. John Canton, “A Method of Making Artificial Magnets Without the Use of Natural Ones,” PT 47 (1751): 31–38. For this work, Canton received the Copley Medal of the Royal Society in 1751.
- 229.
Gowin Knight began reporting his experiments with artificial magnets to the Royal Society in 1744, and in 1747 he was awarded the Copley Medal for his magnetic experiments. Like Canton, because he was unsure he could demonstrate his experiments before the Society with precision, he asked Folkes to observe them at Knight’s lodgings and then to tell the members what he had observed there. 15 November 1744, Journal Book, Royal Society, 18: 304–8. Gowin Knight, “An Account of Some Magnetical Experiments, Shewed before the Royal Society … on Thursday the 15th of November, 1744,” PT 43 (1744): 161–66.
- 230.
Unlike Knight and Canton, Michell did not show his magnets to Folkes or bring them to the Royal Society or communicate a paper on them, but we learn here that in late 1749 or early 1750, he gave Folkes a copy of his “pamphlet,” his Treatise of Artificial Magnets.
- 231.
John Ellicott, 1706–72, instrument-maker, F.R.S. 1738. Taylor, Mathematical Practitioners of Hanoverian England, 156–57.
- 232.
The following testimonial by John Smeaton was published together with Michell’s letter to the editor. “Mr. Smeaton distinctly remembers, that the journey above referred to, was subsequent to the publication of Mr. Michell’s treatise on Artificial Magnets; and that very soon after Mr. Canton’s return from Cambridge, Mr. S. was one of a party at Mr. Canton’s house; of which party was the late Mr. Ellicott and Dr. Knight, since also deceased; when Mr. Canton exhibited the process of Mr. Michell as described in his late treatise: with the ready success of which, the Doctor not only seemed surprised, but declared that he could not have believed, any method could have been found, to have procured so strong a degree of magnetism so expeditiously; with other expressions tending to shew, that Mr. Michell’s process had not been known to the Doctor before: and Mr. S. also remembers, that it was not till some months after this exhibition, that Mr. C. exhibited his experiments to the Royal Society, at which Mr. S. was present; with which Dr. K. was offended irreconcilably; alleging, it was critically timed, as he was then about concluding a treaty with the Navy Board, that his bars might be used in the royal navy: whereas the Doctor remained in friendship with Mr. M. ever after. J. S.”
- 233.
Henri-Louis Duhamel du Monceau, 1700–81, agronomist, chemist, botanist, naval technologist, member of the Academy of Sciences. John Eklund, “Duhamel du Monceau, Henri-Louis,” DSB 4: 223–25. “Façon singulière d’aimanter un barreau d’acier,” Mémoires de mathématique et de physique de l’Académie royale des sciences (Paris, 1745), 181–93.
- 234.
William Ludlam, 1717–88, astronomer, mathematician, writer on theology, fellow of St. John’s College, Cambridge. From 1768, he lived in Leicester. Charles Platts, “Ludlam, William,” DNB, new ed. 34: 712–13.
- 235.
Misc. MS. Collection.
- 236.
Letter 26.
- 237.
Herschel, “On the Construction of the Heavens.”
- 238.
For his “construction of the heavens” in 1785, Herschel assumed that his telescope reached to the edge of the Milky Way. When in 1790 he brought more faint stars into view using a larger telescope, he realized the error of his former assumption.
- 239.
Michell’s paper in 1767, “Probable Parallax.”
- 240.
Herschel regarded the Milky Way as one among numerous nebulas: “As we are used to call the appearance of the heavens, where it is surrounded with a bright zone, the Milky-Way, it may not be amiss to point out some other very remarkable Nebulae which cannot be less, but are probably much larger than our own system.” In the twentieth century, with the identification of extra-galactic, or extra-Milky Way, nebulas, Herschel was proven right. Michell evidently agreed with Herschel on this subject. Herschel, “On the Construction of the Heavens,” 254.
- 241.
J. B. L. Romé de l’Isle, 1736–90, crystallographer, mineralogist. R. Hooykaas, “Romé de L’Isle (or Delisle), Jean-Baptiste Louis,” DSB 11: 520–24. Cristallographie, ou description des formes propres à tous les corps du règne minéral, dans l’état de combinaision saline, pierreuse ou métallique, 4 vols. (Paris, 1783). This is the enlarged, second edition of his Essai de cristallographie in 1772.
- 242.
This was the widely accepted biblical age of the Earth.
- 243.
Around the turn of the seventeenth century, it was generally believed that the original formations of the Earth had been destroyed either by the Flood or by earthquakes and volcanoes, according to a divine plan. In 1740, the Italian geologist Antonio Lazzaro Moro introduced the important distinction between “primitive” and “secondary” rocks. The distinction was further developed by his countryman Giovanni Arduino in 1759, by the German geologists Johann Gottlob Lehmann in 1756, Peter S. Pallas in 1777, and Abraham G. Werner in 1786, by the French geologists Guillaume-François Rouelle and Nicolas Desmarest, and by the Swiss geologist Horace-Bénédict de Saussure in 1779. They regarded primitive rocks as belonging to the original outer layer of the Earth, having precipitated from a chaotic fluid, and secondary rocks as being more recent, formed from deposits on the ocean bed. Primitive mountains were made from granite, basalt, and other primitive rocks, which unlike secondary rocks did not contain organic fossils. Primitive rocks correspond to our igneous and metamorphic rocks, secondary rocks to our sedimentary rocks. Gordon L. Davies, The Earth in Decay: A History of British Geomorphology, 1578–1878 (New York: American Elsevier, 1969), 103–6. Frank Dawson Adams, The Birth and Development of the Geological Sciences (Baltimore, MD: Williams & Wilkins, 1938), 372–93. Jean Jones, Hugh S. Torrens, and Eric Robinson, “The Correspondence between James Hutton (1726–1797) and James Watt (1736–1819) with Two Letters from Hutton to George Clerk-Maxwell (1715–1784): Part I,” Annals of Science 51 (1994): 637–53, on 643–44.
- 244.
Granite is a hard, crystalline, igneous rock composed mainly of quartz, orthoclase-feldspar, and mica.
- 245.
Gypsum, a mineral consisting of hydrous calcium sulfate, in crystalline or foliated form, from which plaster of Paris is made.
- 246.
Finely divided earthy matter composed mainly of hydrous aluminum silicates.
- 247.
Carl Linnaeus, 1707–78, Swedish botanist, zoologist, geologist, professor of medicine at the University of Uppsala. He believed that the formation of sedimentary strata requires a great length of time, but “mindful of ecclesiastical orthodoxy, he was wary of expressing his heretical views on the age of the world and the length of the geographical epochs.” Sten Lindroth, “Linnaeus (or Von Linné), Carl,” DSB 8: 374–81, on 379.
- 248.
Chalk, a soft, amorphous, white limestone, formed from the calcite plates of single-cell algae.
- 249.
Matter containing or resembling the common mineral calcite, or calcium carbonate, which includes limestone, chalk, and marble.
- 250.
It is now estimated that the original 3,000 feet of chalk came largely from the deposit of unicellular organisms on the sea floor, accumulated over 30 million years. If we accept these numbers, Michell’s 400 feet of chalk would have required about five million years, or ten times Michell’s estimate based on animal and vegetable matter per acre in Europe. Shepherd, Flint, 51.
- 251.
John Michell, “Conjectures Concerning the Cause, and Observations upon the Phaenomena of Earthquakes; Particularly of That Great Earthquake of the First of November, 1755, Which Proved So Fatal to the City of Lisbon, and Whose Effects Were Felt as Far as Africa, and More or Less throughout Almost All Europe,” PT 51 (1760): 566–634.
- 252.
James Stuart, 1713–88, painter, architect, and scholar of Greek antiquities, known in his day as “Athenian Stuart.” David Watkin, “Stuart, James,” DNB, new ed. 53: 161–65.
- 253.
Strata of dark, usually black, rock derived from plants.
- 254.
Limestone, a rock constituted mainly of calcium carbonate, derived from organic remains, so named because when it is burnt it produces lime.
- 255.
Henry Cavendish, “Experiments on Air,” PT 75 (1785): 372–84.
- 256.
William Morgan was not then a fellow of the Royal Society, but five years later he would become one, and he would twice be elected to serve on its council. As chief actuary of the Equitable Assurance Society, he was a pioneer of scientific life insurance, and with Priestley’s encouragement he carried out experiments on electricity and combustion. Thomas, “Morgan.”
- 257.
Cavendish and Blagden did not act on Michell’s invitation in 1785, but they did the following year.
- 258.
This gathering probably took place in June 1772, when Pringle and Franklin visited Priestley in Leeds to observe his important experiments on gases (kinds of “air”). Joseph Priestley to Benjamin Franklin, 13 June 1772, in Priestley, Autobiography, 102–3; Schofield, Enlightenment, 163. There is a reference to the visit in Joseph Priestley, “Observations on Different Kinds of Air,” PT 62 (1772): 147–252, on 195–96. I thank Dr. Josephine Lloyd for pointing out the reference in Priestley’s paper.
- 259.
Sir Joseph Banks.
- 260.
Michell had acted on this suggestion twenty-five years earlier. In his paper on earthquakes, he cited a large number of papers from the Philosophical Transactions, giving both the issue of the regular journal and the corresponding abridgment, and he further identified the abridgment with the editor’s name; over the span he covered, the abridgment had four editors.
- 261.
The nature of his illness is unknown.
- 262.
The source of this confusion is clarified in Letter 29.
- 263.
Blagden Letterbook, 1783–87, Osborn Shelves fc15.
- 264.
Paul Henry Maty, 1745–87, under-librarian of the British Museum, F.R.S. 1771, secretary of the Royal Society 1778–84. “Maty, Paul Henry,” DNB 13: 78–79.
- 265.
Hutchins, “Experiments for Ascertaining the Point of Mercurial Congelation.”
- 266.
Cavendish, “Observations on Mr. Hutchins’s Experiments for Determining the Degree of Cold at Which Quicksilver Freezes.”
- 267.
The likely reason for the confusion in the printing of this volume of the Philosophical Transactions was a dispute within the Royal Society in the winter of 1783–84 over the conduct of its president, Sir Joseph Banks. When Banks’s party prevailed, Banks’s opponent Maty resigned as secretary of the Royal Society in charge of its journal. He was replaced by Banks’s ally Blagden, who at the time of this letter to Michell was still picking up the pieces. Jungnickel and McCormmach, Cavendish, the Experimental Life, 335–54.
- 268.
An earth containing or related to the common mineral silica, or silicon dioxide, which occurs in crystal form as quartz. Eighteenth-century mineralogists recognized several kinds of earth, which together with the metals, salts, and substances containing sulfur comprised the Earth’s crust. Rachel Laudan, From Mineralogy to Geology: The Foundations of a Science, 1650–1830 (Chicago and London: University of Chicago Press, 1987), 21–28.
- 269.
An earth containing aluminum or alum.
- 270.
A hydrated double salt of potassium sulfate and aluminum sulfate.
- 271.
A soft mineral with a greasy feel, consisting of a hydrated silicate of magnesium.
- 272.
Another name for the mineral feldspar, consisting of aluminum silicates combined with potassium, sodium, calcium, or barium, a constituent of nearly all crystalline rocks.
- 273.
A white, alkaline earth, or magnesium oxide.
- 274.
Presumably the “heavy earth” in Torbern Olof Bergman’s mineral classification, as given in his Outlines of Mineralogy, trans. W. Withering (Birmingham, 1783).
- 275.
Johann Christian Wiegleb, 1732–1800, German apothecary and chemist. Gunther Kerstein, “Wiegleb, Johann Christian,” DSB 14: 332–33.
- 276.
Freestone, a fine-grained sandstone or limestone, permitting of easy sawing.
- 277.
Stony, reef-building corrals.
- 278.
In these animals, the corral-like skeleton is covered with tiny pores.
- 279.
The Willey coke furnace that Blagden visited at Coalbrook Dale was built by the New Willey Company, which in 1757 had taken over the original Darby coke furnace at Willey; it discontinued operating the furnace in 1774. Both furnace complexes were controlled by John Wilkinson. J. R. Harris, “Wilkinson, John,” DNB, new ed. 58: 1010–13, on 1010.
- 280.
Rudolf Erich Raspe, 1737–94, German geologist who settled in England, where he engaged in mining, F.R.S. 1769. Albert V. Carozzi, “Raspe, Rudolf Erich,” DSB 11: 302–5.
- 281.
Decomposed rock in the outcrop of a metallic vein, reddish in color due to oxydized iron pyrites.
- 282.
Natural magnets.
- 283.
Crumbly residue of metals and minerals after combustion or other means of oxidation.
- 284.
Carl Wilhelm Scheele, 1742–86, chemist, pharmacist, Swedish Academy of Sciences. Uno Boklund, “Scheele, Carl Wilhelm,” DSB 12: 143–50.
- 285.
“Cold-short,” quality of brittleness when cold, applied to iron. Scheele in 1785 showed that the cause of cold-shortness in iron is iron phosphide. J.R. Partington, A History of Chemistry, vol. 3 (London: Macmillan, 1962), 194.
- 286.
Johann Carl Friedrich Meyer, 1733–1811, German chemist, apothecary. Partington, History of Chemistry 3: 580.
- 287.
Tobern Olof Bergman, 1735–84, Swedish chemist, mineralologist, Swedish Academy of Sciences. W.A. Smeaton, “Bergman, Tobern Olof,” DSB 2: 4–8.
- 288.
In 1781–82, Meyer attributed cold-shortness of iron to a new metal “hydrosiderum,” but later he found it to be iron phosphide. In 1781, Bergman tried to prove that cold-shortness is caused by a white earth (basic ferrous phosphate?). Partington, History of Chemistry 3: 194.
- 289.
Prussian blue, a deep blue pigment, derived from iron, consisting mainly of hydrated ferric ferrocyanide.
- 290.
Joseph Louis Proust, 1754–1826, French chemist, who spent most of his career teaching chemistry in Spain. Seymour Mauskopf, “Proust, Joseph Louis,” DSB 11: 166–72.
- 291.
Bergman’s name for the acid that Proust reported. It was contained in sal perlatum, a salt which F. G. Haupt recognized in the heated residue of evaporated urine in 1740. It was identified as a phosphate of soda by H. M. Rouelle in 1776, a finding confirmed by Scheele and Klaproth in 1785 and S. F. Hermstädt in 1786. Partington, History of Chemistry 3: 67, 642.
- 292.
Ignaz von Born, 1742–91, author of Ueber das Anquicken der gold- und silberhältigen Erze, Rohsteine, Schwarzkupfer und Hüttenspeise (Vienna, 1786).
- 293.
Comte de La Garaye, a philanthropist, converted his castle in Brittany into a hospital, and made medicines including a mercurial tincture by a chemical process taking several months. He offered to reveal the secret of his remedies for a price, the money to go to financing his hospital. Ordered by a court to look into it, the chemist P. J. Macquer found the tincture to be nothing but a solution of corrosive sublimate (mercuric chloride) in spirit of wine (alcohol), but the king of France paid a high price for the secret anyway. Partington, History of Chemistry 3: 88–89.
- 294.
Blagden and Cavendish visited Michell next summer. See Letter 32.
- 295.
In the month of this letter, the king granted Herschel £2,000 for materials and assistance in constructing his great telescope. There was a cost overrun, and two years later the king granted him a second £2,000 and £200 a year for maintenance and assistance in operating the telescope. Sidgwick, Herschel, 128–29.
- 296.
The casting was done in London, but otherwise the giant telescope was built at Slough, where Herschel lived.
- 297.
Smeaton Machine Letters 4: 150. Smeaton’s machine letters are copies of outgoing letters, bound in letter books.
- 298.
Smeaton Machine Letters 4: 160.
- 299.
We do not have Michell’s letters to Smeaton of 6 and 7 November, but Smeaton’s reply tells us that they discuss Michell’s help with Smeaton’s book-in-progress on the Eddystone Lighthouse, Michell’s objections to the recent biography of John Canton, Michell’s ongoing work on his great telescope, and Michell’s dispute with Herschel over the cause of indistinct vision.
- 300.
The corrections were to the manuscript of Smeaton’s book on the construction of the Eddystone lighthouse, completed in 1759. Located on a dangerous reef off Plymouth, built entirely of stone, Smeaton’s lighthouse would stand for over a hundred years. He was awarded the Copley Medal of the Royal Society for this early work, which established him as an engineer of the first rank. In the preface to his book many years later, he acknowledged his “friends in the country,” Michell and another colleague, “for purusing and abundantly correcting” his manuscript. We see from this letter that in addition to “Masterly corrections,” Michell supplied Smeaton with matters of technical and historical substance. John Smeaton, A Narrative of the Building and a Description of the Construction of the Edystone Lighthouse with Stone … , 2d ed. (London, 1793).
- 301.
John Rudyerd, fl.1703–09, came from Cornwall, and was in the service of a gentleman. He designed and built the second Eddystone lighthouse–the first was destroyed by a gale in 1703 after only five years–made of wood lined with stone, and completed in 1706. When in 1755 it was destroyed by fire, the president of the Royal Society recommended Smeaton as the engineer to design and build the third lighthouse. Smeaton had great respect for his predecessor’s work on the lighthouse. “Smeaton,” DNB 18: 393. James Hodge, “Rudyerd, John,” DNB, new ed. 48: 93.
- 302.
Henry Eastburn, 1753–1821, civil engineer, Smeaton’s nephew and his apprentice in 1768 and assistant in 1775–88. “Eastburn, Henry,” in A. W. Skempton, A Biographical Dictionary of Civil Engineers in Great Britain and Ireland (London: Thomas Telford, 2002).
- 303.
therse.
- 304.
Smeaton begins his book on the Eddystone lighthouse with a description of the most celebrated lighthouse of antiquity, the Pharos of Alexandria.
- 305.
A recent biography of Canton probably accounts for Michell’s “Cantonian anecdotes” in his letter or letters to Smeaton in 1785. See Letter 27 and note 11 below for the background of Michell’s unhappiness with Canton.
- 306.
Michell’s avoidance of “expressions of Dissenting Interest” may mean that his anecdotes dealt with matters of fact and not with Michell’s opinion of Canton’s integrity, or it may refer to ministers and other Dissenters who were Canton’s good friends.
- 307.
Canton carried out important experiments on electrical induction and other electrical phenomena in the 1750s, and he was the first in England to confirm Franklin’s hypothesis that lightning is electrical. He provided Priestley with copious “advice, instruction, and correction” during his writing of The History and Present State of Electricity, with Original Experiments (London, 1767). Schofield, Enlightenment, 142. What Smeaton refers to as Canton’s “gross duplicity” in regard to electricity is unexplained.
- 308.
An abbreviated version of the biography of Canton appearing in the Biographica Britannica in 1784 was published in the Monthly Review 71 (1784): 321–28.
- 309.
William Canton, the source of information for the biography of his father, John.
- 310.
Gowin Knight, magnetic experimenter and maker of artificial magnets.
- 311.
Michell made the case on his own behalf in his letter to the editors of the Monthly Review, supported by a testimonial by Smeaton. The wording of the present letter suggests that Smeaton had not yet written his testimonial. Michell’s letter to the editors was dated in May of this year, but the issue of the journal may not have come out until after this letter by Smeaton. See Letter 27.
- 312.
John Smeaton, “Observations on the Graduation of Astronomical Instruments; with an Explanation of the Method Invented by the Late Mr Hindley, of York, Clockmaker, to Divide Circles into Any Given Number of Parts,” PT 76 (1786): 1–47.
- 313.
Jesse Ramsden, 1735–1800, London instrument-maker, F.R.S. 1786. Roderick S. Webster, “Ramsden, Jesse,” DSB 11: 284–85.
- 314.
It would be well over a year before Herschel made his first viewing with this telescope, on 19 February 1785. William Herschel, “Description of a Forty-feet Reflecting Telescope,” PT 85 (1795): 347–409, on 349–50.
- 315.
Caroline Herschel, William’s sister, wrote in her autobiography, “At one time no less than 24 men (12 and 12 relieving one another) kept polishing, day and night, and my Brother of course never leaving them all the while.” Quoted in Sidgwick, Herschel, 134.
- 316.
On the king’s purse, see Letter 29.
- 317.
Or worst.
- 318.
The structure of the human eye enters the dispute between Michell and Herschel on the subject of indistinct vision; Blagden and Cavendish were drawn into this dispute. See Letter 37.
- 319.
The other half of the quotation marks is missing.
- 320.
Smeaton’s term for the craft of his fraternity, “engineery,” enters as “The science of engineering. SMEATON” in the Oxford Universal Dictionary, 3rd ed. (Oxford: Clarendon Press, 1955), 611.
- 321.
Samuel Johnson, 1709–84, critic, literary biographer, poet, and in 1755 author of the celebrated English dictionary known by his name. “Johnson, Samuel,” Webster’s Biographical Dictionary (Springfield: G. & C. Merriam, 1970), 789.
- 322.
Smeaton planned to devote the remaining years of his life to the project he describes in this letter, but his book on the Eddystone lighthouse was the only account he lived to complete. “Smeaton,”DNB 18: 395.
- 323.
Blagden Letters, 7.21
- 324.
On their journey to northern England to study its geology and industry that summer, Cavendish and Blagden stayed with Michell twice, the second time for six days. Entry for 2 September 1786, Charles Blagden Diary, Yale. Charles Blagden to John Blagden Hale, 14 September 1786, draft, Blagden Letters, Royal Society Library, 7: 33.
- 325.
Caroline Lucretia Herschel, 1750–1848, astronomer, singer. She assisted her brother William in making astronomical observations, and on her own she discovered eight comets, the first of which she announced in 1786: Caroline Herschel, “An Account of a New Comet,” PT 77 (1787), 1–3. Michael A. Hoskin, “Herschel, Caroline Lucretia,” DSB 6: 322–23.
- 326.
The president of the Royal Society together with appropriate members were charged with making regular inspections of the Royal Observatory at Greenwich, called “visitations.”
- 327.
This speed equals that of the best known clocked trial of a “sailing chariot”–Lawrence Sterne refers to it in Tristram Shandy, for instance–that of Prince Maurice and twenty-seven other passengers in a two-masted wagon on a beach in Holland in 1602. Designed by the Prince’s engineer Simon Stevin, the chariot covered forty-two miles in two hours. The Rijksmuseum in Amsterdam has a print of this event.
- 328.
Blagden Letters, 7.37.
- 329.
Cavendish and Blagden.
- 330.
William Beatson, 1757–1825, together with his cousin Robert Beatson, 1750–90, operated a glassworks in Rotherham, near Sheffield. Founded in 1751, since 1783 it was known as W. Beatson & Co. The Glass Works. Rotherham, 1751–1951 (Rotherham: Beatson, Clark, 1952), 5–10.
- 331.
Shortly before the glassworks, an iron foundry was started in Rotherham by Samuel Walker. Glass Works, 5. See Letter 11, note 10.
- 332.
Cavendish’s townhouse in London.
- 333.
Called “kish” by the workmen, and “black lead” by Michell, plumbago is a black, shiny, imperfect form of graphite that separates from certain iron in smelting. Cavendish and Blagden had gone to Rotherham to enquire after the “remarkable circumstance” they had learned from Beatson that in the extraction of iron from its ore at Walkers’ furnaces large quantities of plumbago were produced. At the furnaces, they were disappointed, however, since they “could not see any of the plumbago or Kish except for a few particles adhering to the cast pigs.” Told that they might see some plumbago at Smith’s furnace in Chesterfield, they went there next, but again they were unable to get a sizeable sample. Cavendish Scientific Manuscripts, Devonshire Collections, Chatsworth, X(a), 3: 9. Charles Blagden to Sir Joseph Banks, 17 September 1786, BL Add Mss 33272, 9–10. Beatson provided the plumbago requested in this letter. In his analysis of it, Cavendish compared it with a sample of “kish iron” brought back from Chesterfield: “Kish or Plumbago from Beatson,” in “White Book,” Cavendish Scientific Manuscripts, ibid., 57–58.
- 334.
William Matthewman, manufacturer of spotted knives; Wadsley is in the neighborhood of Sheffield. A Directory of Sheffield, compiled by J. Gales and D. Martin (London, 1787), 41.
- 335.
William Marshall, cutlery (couteaux) manufacturer; Bents Green is in the neighborhood of Sheffield. Ibid., 20.
- 336.
The Gregory lead mine in Overton, Derbyshire belonged to the Banks family, passing to Sir Joseph Banks, president of the Royal Society, in 1792. This mine was once the richest in the country, but in the 1780s the returns dropped off sharply. Hugh Torrens, “Patronage and Problems: Banks and the Earth Sciences,” in Sir Joseph Banks, A Global Perspective, ed. R.E.R. Banks, B. Elliot, J.G. Hawkes, D. King-Hele, G.Ll. Lucas (Kew: Royal Botanic Gardens, 1994), 49–75, on 53.
- 337.
Gritstone is a coarse form of sandstone, used for grindstones and millstones. Arkell and Tomkieff, English Rock Terms, 52–53.
- 338.
“Toadstone” is a term used by Derbyshire lead-miners, derived from the German Todstein, or dead stone, so named because this stone contains no lead ore, unlike the limestone in which it is embedded. H.S. Torrens, “Erasmus Darwin’s Contributions to the Geological Sciences,” in The Genius of Erasmus Darwin, ed. C.U.M. Smith and R. Arnott (Ashgate, 2005), 259–72, on 265. In the previous decade, the French geologist Nicolas Desmarest had correctly identified toadstone as basalt.
- 339.
Rock formed of clay, silt, or mud, with a laminate structure.
- 340.
Finely divided earthy matter consisting mainly of aluminum silicate, derived from decomposed felspar and other minerals.
- 341.
John Whitehurst, 1713–88, geologist and clockmaker, described and discussed the origin of Derbyshire toadstone in his main publication, An Inquiry into the Original State and Formation of the Earth … (London, 1778). In the year of this letter, a second, enlarged edition of the book came out. John Challinor, “Whitehurst, John,” DSB 14: 311–12.
- 342.
In their letters, Michell, Blagden, and Cavendish recognize Michell’s yellow limestone and Blagden’s yellow limestone as distinct strata. In his table of strata of southern England, Michell calls his yellow limestone, which lies over the coal, “Roch Abbey and Brotherton limes”; Blagden’s yellow limestone, which lies over the blue lias, is higher in the sequence. Without the aid of fossils, the two yellow limestones cannot be distinguished lithographically. Communication from Hugh Torrens.
- 343.
Southeast of Leicester.
- 344.
Southeast of Market Harborough, near Milton Keynes.
- 345.
Alexander Aubert, 1730–1805, astronomer, governor of the London Assurance Company, F.R.S. 1772. “Aubert, Alexander,” DNB 1: 715.
- 346.
Jean-François de la Pérouse, French explorer. On a voyage of discovery in the Pacific, having last been seen at Botany Bay in Australia in March 1788, his two vessels were wrecked in the New Hebrides with the loss of all hands. Robert Hughes, The Fatal Shore (New York: Vintage Books, 1988), 86–88.
- 347.
This was an early self-propelled steam engine, but not the first. The first model steam carriage was built in 1763 by a French engineer. Regarded as sufficiently promising for the French government to invest in a full-size version, the carriage traveled at 2¼ miles an hour, but because it proved unstable it was regarded as a public danger, and it was withdrawn from use. In Britain, in 1759 John Robison urged James Watt to power a carriage by a steam engine, and in 1784 Watt included a locomotive in his patent for a steam engine, but he did not pursue it; when one of his employees built a model locomotive, he considered it a diversion and discouraged the builder. In 1765 Erasmus Darwin urged Watt’s partner Matthew Boulton in the same direction, also without success. In 1797, Richard Trevithick made a model locomotive, and in the early years of the nineteenth century he built and tried several full-size locomotives, including the first to run on rails instead of a road, but he received little encouragement and turned to other projects. Before long, locomotives were built for hauling coal over rail lines. In 1825 George Stevenson completed the first public railway using steam-powered locomotion, transporting passengers as well as freight between Stockton and Darlington. Wolf, History of Science, Technology, and Philosophy in the 18th Century 2: 554–55. “Railway,” Encyclopaedia Britannica 18: 927–50, on 927–28.
- 348.
Formerly Ann Brecknock, 1736–1818; Michell’s second wife.
- 349.
Gilbert Michell, 1726–92; John’s brother.
- 350.
Blagden Letters, 7.49.
- 351.
William Herschel, “Investigation of the Cause of That Indistinctness of Vision Which Has Been Ascribed to the Smallness of the Optic Pencil,” PT 76 (1786): 500–7.
- 352.
That year Herschel and his sister, Caroline, moved to Slough and into the Observatory House, as it was later known.
- 353.
The diameter of the tube was four feet ten inches.
- 354.
Charles Francis Greville, 1749–1809, mineralogist and horticulturist, F.R.S. 1772. Beginning in 1773, Greville built a large mineral collection, including rare specimens. Passing to the British Museum after his death, this collection together with Charles Hatchett’s raised the Museum’s collection to the first rank. Michael P. Cooper, “Greville, Charles Francis,” DNB, new ed. 23: 782–83. Edward Miller, That Noble Cabinet: A History of the British Museum (Athens: Ohio University Press, 1974), 113.
- 355.
Cavendish Scientific Manuscripts. This letter is published in Jungnickel and McCormmach, Cavendish, the Experimental Life, 631–33.
- 356.
We do not have Cavendish’s letter to Michell of 6 November 1786, but we can be certain that it continued their discussions of that summer.
- 357.
Cavendish hired scientific assistants. Two years earlier, Charles Cullen, son of the Scottish physician and chemist William Cullen, worked for Cavendish. For his great telescope and other scientific projects, Michell, too, had an assistant, whom he referred to as his “operator.” Charles Cullen to Charles Blagden, 7 November 1784 and “Monday” [1784], Blagden Letters, Royal Society, C.62 and 63. John Michell to Charles Blagden, 10 March 1788, Letter 41.
- 358.
Letters of 19 September and 31 October 1786: Letters 33 and 34.
- 359.
Named after a Neapolitan banker, tontine was a financial scheme whereby subscribers to a loan or fund were paid annuities, which increased in value as their numbers died off, in the end leaving the last survivor in possession of the entire fortune.
- 360.
Herschel, “Investigation of the Cause of That Indistinctness of Vision Which Has Been Ascribed to the Smallness of the Optic Pencil.” At Herschel’s request, Cavendish had given him his criticisms of this paper. Henry Cavendish to William Herschel, 1 June 1786, Herschel MSS, Royal Astronomical Society, W 1/13, C.17.
- 361.
None of Michell’s letters to Smeaton is known to have survived.
- 362.
Banks Correspondence, l.256.
- 363.
William Pashley, 1738–93, educated at Cambridge University, rector of Grove, Nottinghamshire, 1749–93, and rector of Barlborough, Derbyshire, 1764–93. Alumni Cantabrigienses 1: 316.
- 364.
On his and Cavendish’s visit to Thornhill that fall, Blagden wrote to Banks about a remarkable ash tree he observed in the churchyard there. Charles Blagden to Sir Joseph Banks, 4 September 1786, Banks Correspondence, British Library Add. MS. 33272, 7–8.
- 365.
Richard Anthony Salisbury, of Chapel Allerton, Yorkshire. On 14 October 1786, Michell recommended Salisbury for membership in the Royal Society, citing his knowledge of natural history; he was elected on 15 March 1787. Certificate Book, Royal Society Library.
- 366.
Carl Linnaeus, Dissertation on the Sexes of Plants. Translated from the Latin of Linnaeus, trans. J.E. Smith (London, 1786).
- 367.
Letter 37.
- 368.
Misc. MS. Collection.
- 369.
Letters 33 and 34.
- 370.
Herschel, “Investigation of the Cause of that Indistinctness of Vision Which Has Been Ascribed to the Smallness of the Optic Pencil.”
- 371.
Blagden showed Michell’s letter to Cavendish, who wrote out two sheets of comments, which are kept with this letter. At this place in the letter, Cavendish comments, “According to M[ichell]s theory I think H[erschel] cannot be said to object even rather improperly to what has been said.”
- 372.
Here Cavendish comments, “The pencils are really very small but not brought to a very small focus.”
- 373.
Letter to Cavendish on 8 November 1786.
- 374.
Disagreeing with Michell’s explanation, Cavendish states his own: “I should not attribute the effect to any thing in the form of the eye or its thready nature but to the nature of the retina or optic nerve namely that when one fibre of it was affected very differently either in point of light or colour from another contiguous fibre it sufferd an irregular irritation which in some cases it communicated to fibres at a great distance from it.”
- 375.
Robert Smith translates Huygens’s passage: “For by looking through an hole, in a thin plate, narrower than 1/5 or 1/6 of a line, the edges of objects begin to appear confused and so much the more as the hole is made narrower.” A line is 1/8th of an inch. Smith, Opticks, 245.
- 376.
We do not have Michell’s letters to Smeaton, but we do have a letter from Smeaton, written a year and a half earlier, asking Michell to clarify his ideas on the structure of the eye, by which Michell explains the indistinctness of images formed by small pencils of light. Smeaton to Michell, 23 November 1785, Letter 31.
- 377.
Cavendish proposes an experiment: “The small hole seems to present a way of putting the theory to the proof If the object is indistinct when placed in the focus of the eye & not when removed from it [it] will be a strong proof of the truth of it If it does not I do not know how to reconcile it with it.”
- 378.
A piece is torn from the letter affecting several lines.
- 379.
In translation: “Another is the reason that when the hole has been made excessively narrow, the clear outline of the images vanishes; of course, it comes about that to the degree to which the aperture is narrowed, by so much narrower a pencil do the rays which proceed from any given point of the object reach the eye.”
- 380.
Gilbert Michell, who was then living at Thornhill.
- 381.
Blagden Letterbook, 1783–87, Osborn Shelves fc15.
- 382.
William Herschel, “Account of Three Volcanos in the Moon,” PT 77 (1787): 229–31. The moon once had active volcanoes, but not in Herschel’s time.
- 383.
Misc. MS. Collection.
- 384.
Letter 38.
- 385.
Whitby, a port on the coast of North Riding of Yorkshire.
- 386.
Jet rock is a hard, dense, black form of lignite coal.
- 387.
A hard, usually grey stone with white incrustations, occurring in nodules; a variety of chert found in chalk beds; see next note.
- 388.
A hard, stratified rock composed mainly of silica derived from the shells of single-cell animals, occurring in nodules.
- 389.
Lias is a blue limestone rock found in southwest England, usually banded with clay and shale.
- 390.
Anthracite, a hard coal.
- 391.
William Hamilton, 1730–1803, Scottish diplomat, art collector, and student of volcanoes, F.R.S. 1766. Albert V. Carozzi, “Hamilton, William,” DSB, 6: 83–85.
- 392.
Promontory of basaltic rock columns off the northern coast of County Antrim, Northern Ireland. The columns are a foot or two across and rise to a height of twenty feet or so, forming a causeway up to forty feet in width. Folklore attributes it to a race of giants, who built it to connect with Staffa, where there are similar, much taller columns; see next note. The columns are prismatic, occasioned by the rapid cooling of lava flowing into the sea. “Giant’s Causeway,” Encyclopaedia Britannica, 1962, 10: 337. William Hamilton, Letters Concerning the Northern Coast of the County of Antrim (Dublin, 1786).
- 393.
Staffa, a small island off the west coast of Scotland. On an expedition to Iceland in 1772, Banks stopped at the island, where near Fingal’s Cave he observed basaltic pillars fifty or more feet high, “past all description,” noting their similarity to the Giant’s Causeway. His description, sketches, and measurements brought Staffa to the attention of the scientific world; they were published in Thomas Pennant, A Tour in Scotland and Voyage to the Hebrides in 1772, 2 vols. (London, 1774) 1: 265. J. Challinor, “The Early Progress of British Geology.– II. From Strachey to Michell, 1719–1788,” Annals of Science 10 (1954): 1–19, on 10–12. Torrens, “Patronage and Problems: Banks and the Earth Sciences,” 52.
- 394.
That is, the Giant’s Causeway.
- 395.
Basalt, a dark, fine-grained igneous rock, usually originating with a lava flow, often forming columnar strata.
- 396.
On the northern coast of Northern Ireland.
- 397.
Rathlin Island, off the coast of Northern Ireland.
- 398.
Thomas Pennant, 1726–98, naturalist, traveler, writer, F.R.S. 1767. Charles W. Withers, “Pennant, Thomas,” DNB, new ed. 43: 568–71.
- 399.
The Hebrides, islands off the west coast of Scotland. See note 1 l.
- 400.
Large island off the west coast of Scotland.
- 401.
Islands off the north coast of Scotland.
- 402.
The estuary Firth of Lorne, on the west coast of Scotland.
- 403.
Jura and Islay are adjacent, large islands off the west coast of Scotland.
- 404.
Oransay and Colonsay are neighboring islands off the west coast of Scotland.
- 405.
James Dorret, land surveyor. His first map of Scotland appeared in 1750, his second in 1751, and his third in 1761. The latter appeared the same year as this letter in The Large English Atlas, eds. A. Armstrong, E. Bowen, and T. Kitchen, 1787 edition. Committee of the Royal Scottish Geographical Society, The Early Maps of Scotland to 1850, 3rd ed., rev. D. G. Moir (Edinburgh: Royal Scottish Geographical Society, 1973), 191.
- 406.
Canna Island off the west coast of Scotland.
- 407.
Town near Thornhill.
- 408.
Michell’s first grandchild, Mary Turton, born 1 June 1787. Nine months earlier, on 2 September 1786, Michell’s daughter of the same name, Mary, married Thomas Turton, by which marriage Michell acquired seven grandchildren, six girls and one boy. “Turton, Sir Thomas,” in R.G. Thorne, The History of Parliament: The House of Commons, 1790–1820, vol. 5: Members Q-Y (London: History of Parliament Trust, 1986), 420–22.
- 409.
Blagden Letters, 7.341.
- 410.
Probably William Winlaw, engine-maker and inventor, who lived at 72 Margaret Street, Cavendish Square in London. Will of 1 December 1795, TNA PRO PROB 11/1282.
- 411.
This letter is missing.
- 412.
Blagden Letters, 7.354.
- 413.
Blagden and Cavendish had recently returned from their journey into southwestern England, where they observed the geology, the clay pits, the copper and tin mining and smelting, and the steam engines used to raise ore and to pump water from mines; they also measured elevations barometrically and set up a meteorological station on Dartmoor. Journal, 15 July–10 August, Cavendish Scientific Manuscripts, Devonshire Collections, Chatsworth, X(a), 6, 7.
- 414.
James Watt, 1736–1819, engineer, inventor, F.R.S. 1785. A large number of Watt’s improved steam pumping engines were installed in Cornish mines. “Watt, James,” DNB 20: 962–73.
- 415.
Killas, Cornish name for a schistose stone. On their tour, Blagden and Cavendish frequently observed this stone, which comprises a major part of the rocky mass surrounding the tin and copper. “Cornwall consists chiefly of Killas,” Cavendish wrote in his journal of the tour. Cavendish Scientific Manuscripts, X(a), 6, 7.
- 416.
“Elvan,” Cornish word for a hard, intrusive, igneous rock such as quartz-porphyry. Blagden and Cavendish were informed that metallic ore is sometimes richer in elvan than in killas. Ibid.
- 417.
Near the end of the peninsula in Cornwall.
- 418.
St. Austell is just up the peninsula from Redruth. Polgooth Mine is a tin mine a mile and a half from St. Austell. At the mine, Blagden and Cavendish descended by ladder 100 fathoms into the load, which runs nearly vertically. Cavendish Scientific Manuscripts, Devonshire Collections, Chatsworth, X(a), 6.
- 419.
In Dorsetshire, on the English Channel.
- 420.
In Devonshire, west of Bridport.
- 421.
Hill between Exeter and Teignmouth. Spelled by Blagden and Cavendish “Hall down” and “Halldown,” Sir Archibald Geikie spells it “Halldon.” Memoir of John Michell … (Cambridge: Cambridge University Press, 1918), 62.
- 422.
A large moor in Devonshire, between St. Austell and Exeter.
- 423.
Horace Bénédict de Saussure, 1740–99, Swiss geologist, meteorologist, and botanist, F.R.S. 1788. The reference is to his Voyages dans les Alpes … , vol. 2 (Neuchâtel-Geneva, 1786). Albert V. Carozzi, “Saussure, Horace Bénédict de,” DSB 12: 119–23. One of the objects of Cavendish and Blagden’s journeys was to measure the height of mountains using a barometer, a subject of considerable interest at the time. Cavendish, as always, was as interested in the instrument as in the observations made with it; the experiment on Dartmoor is an example. Chatsworth has a portable barometer belonging to Henry Cavendish, probably one he took along on their journeys.
- 424.
William Roy, 1726–90, military engineer and surveyor, was appointed by the government to lay triangles between London and Dover, there to connect with triangles laid from Paris, with the object of determining the relative positions of the royal observatories at Greenwich and Paris. “Roy, William,” DNB 17: 371–73.
- 425.
Jesse Ramsden, 1735–1800, instrument-maker, F.R.S. 1786. For the Paris-Greenwich triangulation, General Roy commissioned Ramsden to make a theodolite of high precision; Ramsden spent three years making it. Roderick S. Webster, “Ramsden, Jesse,” DSB 11: 284–85.
- 426.
Jean-Dominique Cassini, 1748–1845, director of the Paris Observatory, member of the Institut National. René Taton, “Casini, Jean-Dominique,” DSB 3: 106–7.
- 427.
Misc. MS. Collection
- 428.
Letters 40 and 41.
- 429.
Siliceous earth, matter consisting mostly of the mineral silica, or silicon dioxide, which in the form of quartz enters into the composition of many types of rocks. It was one of several kinds of earth, which at the time could not be further reduced, but which with the advent of electrochemistry in the early nineteenth century were found not to be elementary. Today we consider siliceous earth to be deposits formed mainly from the silica contained in the skeletons of radiolarian protozoa and the cell walls of diatoms. John Challinor, A Dictionary of Geology, 5th ed. (Cardiff: University of Wales Press, 1978), 279.
- 430.
Calcareous earth, matter consisting mainly of organic remains such as shells and corals, which in turn consist mainly of calcium carbonate.
- 431.
The French mineralogist Jean-André Mongez, 1751–88, translated and annotated Bergman’s manual on mineralogy, which classified minerals into classes, genera, and species with the help of chemical analysis: Manuel du Minérologiste ou Sciagraphie du Regne Minéral distribuée d’après l’Analyse Chimique (Paris, 1784). “Mongez, Jean-André,” in J. C. Poggendorff, Biographisch-Literarisches Handwörterbuch zur Geschichte der exacten Wissenschaften, 2 vols. (Leipzig, 1763) 2:col. 186–87.
- 432.
Bergman regarded metals as made of phlogiston and a calx, an oxide. Partington, History of Chemistry 3: 194.
- 433.
Antoine-Laurent Lavoisier, 1743–94, French chemist, Royal Academy of Sciences, author of the new antiphlogistic chemistry. Henry Guerlac, “Lavoisier, Antoine-Laurent,” DSB 8: 66–91.
- 434.
Clay and shale.
- 435.
Michell here refers to the standard broad classes of minerals in the eighteenth century: metals, sulfur, salts, and earths and stones. Laudan, From Mineralogy to Geology, 21.
- 436.
Peter Woulfe, 1727 [?]–1803, Irish [?] chemist, F.R.S. 1767. E.L. Scott, “Woulfe, Peter,” DSB 14: 508–9.
- 437.
Antoine-Grimoald Monnet, 1734–1817, French chemist, mineralogist, and inspector of mines. Rhoda Rappaport, “Monnet, Antoine-Grimoald,” DSB 9: 478–79.
- 438.
John Woodward, 1665–1728, English geologist, mineralogist, botanist, professor of physic at Gresham College, London, F.R.S. 1693. V.A. Eyles, “Woodward, John,” DSB 14: 500–3. John Woodward, A Catalogue of the Additional Native English Fossils in the Collection of John Woodward M.D. (London, 1728). David Price, “John Woodward and a Surviving British Geological Collection from the Early Eighteenth Century,” Journal of the History of Collections 1 (1989): 79–95, on 94,
- 439.
Harz Mountains, in central Germany.
- 440.
Town in Derbyshire.
- 441.
Rock crystal is a siliceous earth, made of quartz or silica. Diamond at the time was thought to be the purest form of rock crystal. Laudan, From Mineralogy to Geology, 60. We now know diamond to be crystalline carbon.
- 442.
Blagden with Cavendish visited Michell at Thornhill in the summer of 1786.
- 443.
Richard Kirwan, Elements of Mineralogy (London, 1784).
- 444.
Shells of sea-urchins, spheroidal, made of polygonal plates with spines.
- 445.
Aculei are the variously shaped spines of the echinus.
- 446.
A kind of talc, with a soapy feel; soapstone.
- 447.
Probably Thomas Tofield, of Wilsick, who succeeded his father, Thomas, before or in 1750. Conveyance of land from Elizabeth and Thomas Tofield, widow and son of Thomas Tofield deceased, 5–6 April 1750, Sheffield Archives, Melton Hall Deeds, MHD/4.
- 448.
In West Riding of Yorkshire.
- 449.
Near Sheffield.
- 450.
In Derbyshire.
- 451.
Robert Shirley, sixth Earl Ferrers, 1723–87. Burke’s Peerage 1: 1051.
- 452.
In the eighteenth century, land enclosures, commutation of tithes, and construction of turnpikes and canals resulted in better and more detailed maps. Peter Perez Burdett’s map of Derbyshire, with mines marked out, is a good example; published in 1767, it was revised in 1791.
- 453.
Daines Barrington, 1727–1800, judge, antiquary, natural historian, F.R.S. 1767. David Philip Miller, “Barrington, Daines,” DNB, new ed. 4: 63–65. Daines Barrington, “A Letter to Dr. William Watson, F.R.S. … on the Trees Which Are Supposed to Be Indigenous in Great Britain,” PT 59 (1769): 23–38.
- 454.
Siliceous matter
- 455.
Cavendish Scientific Manuscripts, X(b), 15. This letter is published in Geikie, Michell, 47–58, and in Jungnickel and McCormmach, Cavendish, the Experimental Life, 652–55.
- 456.
Greetham Common is near Oakham on the Great North Road, on which Michell would have traveled on his journeys to London.
- 457.
Yellow limestone, apparently the name given to the limestone belonging to the lower oolite group. Geikie, Michell, 48. Geikie annotates his published version of this letter, using modern names for the formations Michell describes. His annotations are transferred to the letter republished here.
- 458.
Geikie writes that this doubtless is the chalky boulder-clay lying unconformably on Jurassic rock. Michell, 48.
- 459.
George Finch, 8th earl of Winchelsea and 4th earl of Nottingham, 1752–1826; his time was “in great measure devoted to agricultural pursuits.” Obituary in Gentleman’s Magazine 96 (1826): 270.
- 460.
This expensive search for coal was ill–advised, for the clay was confused with other clays found in the neighborhood of extractable coal. Torrens, “Darwin’s Contributions,” 260.
- 461.
Town in Lincolnshire.
- 462.
Probably a clay belonging to the upper lias. Geikie, Michell, 53.
- 463.
The rock to the west of Grantham is the upper, middle, and lower lias. Geikie, Michell, 54–55.
- 464.
Foston is on the Great North Road just northwest of Grantham.
- 465.
Great Gonerby, pronounced Gunerby, is also on the Great North Road.
- 466.
This is the magnesian limestone of the permian system, a 150-mile band between Nottingham and the mouth of the Tyne. Geikie, Michell, 56.
- 467.
The tavern where the Royal Society Club dined on Thursdays.
- 468.
Cavendish Scientific Manuscripts. This letter in response to Letter 43 is published in part in Geikie, Michell, 59–63, and in entirety in Jungnickel and McCormmach, Cavendish, the Experimental Life, 656–58.
- 469.
This and the following two paragraphs contain geological observations from Cavendish and Blagden’s journey in the southwest of England from mid-July to mid-August 1787. Cavendish Scientific Manuscripts, Devonshire Collections, Chatsworth, X(a), 6 and 7. Bridport is on Lyme Bay, which is off Cornwall and Devonshire on the English Channel.
- 470.
The geological observations in this letter are from Cavendish and Blagden’s journey into southwest England the year before, in August 1787.
- 471.
Town on Lyme Bay.
- 472.
A “soft sandstone of the colour of red ochre.” Page 11 of a paper without a cataloging number, Cavendish Scientific Manuscripts, Devonshire Collections, Chatsworth, Journals, X(a).
- 473.
Town on Lyme Bay southwest of Sidmouth.
- 474.
There is no punctuation here, and the next words are “& Besides Hall down the top of which …” This is confusing; a period is inserted, and “&” is removed.
- 475.
Neighboring towns on Bristol Channel.
- 476.
Town northwest of London.
- 477.
Cavendish calls Michell’s yellow limestone the “ancient yellow limestone” in his order of strata.
- 478.
The Trent is a tributary of the Humber on the east coast of England, and Scarborough lies on the coast to the north of the Humber estuary.
- 479.
Geikie comments that Cavendish’s letter “contains several interesting original observations,” of which the “most remarkable is that which recognised the important overlap of the Cretaceous series of Yorkshire whereby the whole of the underlying Jurassic formations are concealed for a space of some twenty miles.” Michell, 63–64.
- 480.
On trips to France in 1787, 1788, and 1789, Blagden made geological and mineralogical observations, which he sent to Cavendish; he also brought back specimens of stones, which he gave to Cavendish to subject to chemical examination. Cavendish Scientific Manuscripts, Devonshire Collections, Chatsworth, X(a), 1, 8.
- 481.
A hard, siliceous rock lying directly below the coal-measures.
- 482.
A crumbly earth such as clay, sand, and silt containing substantial amounts of calcium carbonate.
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McCormmach, R. (2012). Letters. In: Weighing the World. Archimedes, vol 28. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-2022-0_7
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