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BJHS 0(0): 1–33, 2017. © British Society for the History of Science 2017. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http:// 1 creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and 2 reproduction in any medium, provided the original work is properly cited. 3 doi:10.1017/S0007087417000802 4 5 6 7 fi 8 Taking Newton on tour: the scienti c travels of 9 Martin Folkes, 1733–1735 10 11 Q1 ANNA MARIE ROOS* 12 13 14 Abstract. Martin Folkes (1690–1754) was Newton’s protégé, an English antiquary, mathem- 15 atician, numismatist and astronomer who would in the latter part of his career become simul- taneously president of the Royal Society and of the Society of Antiquaries. Folkes took a Grand 16 Tour from March 1733 to September 1735, recording the Italian leg of his journey from Padua 17 to Rome in his journal. This paper examines Folkes’s travel diary to analyse his freemasonry, 18 his intellectual development as a Newtonian and his scientific peregrination. It shows how, in 19 this latter area, how he used metrology to understand not only the aesthetics but also the engin- eering principles of antique buildings and artefacts, as well as their context and place in the 20 Italian landscape. Using Folkes’s diary, his account book of his journey in the Norwich 21 archives, and his correspondence with other natural philosophers such as Francesco 22 Algarotti (1712–1764), Anders Celsius (1701–1744) and Abbé Antonio Schinella Conti – ’ 23 (1667 1749), this paper will also demonstrate to what extent Folkes s journey established his reputation as an international broker of Newtonianism, as well as the overall primacy of 24 English scientific instrumentation to Italian virtuosi. 25 26 Introduction 27 ‘ ’ 28 Qui sera sera, Who or What will be, will be is the opening phrase that Martin Folkes – 29 (1690 1754) chose as his personal motto and inscribed in his travel diaries of his Grand 1 30 Tour from 24 March 1733, returning to London on 3 September 1735. Folkes was 31 32 * University of Lincoln, Brayford Pool, Lincoln, Lincolnshire LN6 7TS, UK. Email: [email protected]. 33 Anna Marie Roos is a Reader in the School of History and Heritage at the University of Lincoln and was a Visiting Fellow at All Souls College, Oxford (2017). I would like to thank Jim Bennett, Christopher Foley, 34 Dmitri Levitin, Keith Moore of the Royal Society Library, Sir Noel Malcolm, and the two anonymous 35 reviewers whose encouragement and comments improved and enriched the paper. I would also like to thank 36 the Fellows of All Souls College, Oxford, for granting me a visiting fellowship and for their kindness, 37 generosity and collegiality. 1 Martin Folkes, ‘Journey from Venice to Rome’, MS Eng. misc. c. 444, Bodleian Library; Martin Folkes 38 Esq., ‘Memoranda in case he should go abroad again, respecting his Estates, foreighn money & Places’, 39 NRS 20658, Norwich Record Office, f. 18r. His motto also appears on the mezzotint copy of the 1718 40 portrait of Folkes by Jonathan Richardson. See National Portrait Gallery, NPG D36990. The exact fi 41 translation of this phrase is dif cult, because the exact phrase would not be used with the pronoun qui alone in French, instead beginning with ce qui. The only modern French phrase that gets as close as possible 42 to this fatalistic meaning would be ce qui doit arriver arrivera, which translates ‘what needs to happen will 43 happen’. Used with the verb être/‘to be’ instead of arriver/‘to happen’, an older form of this phrase would 44 be ce qui doit être sera (‘what must be, will be’). This rendition is very close to Folkes’s phrase, where the ce 2 Anna Marie Roos

45 Newton’s protégé, an English antiquary, mathematician, numismatist and astronomer 46 who, in addition to becoming simultaneously president of the Royal Society and of 47 the Society of Antiquaries, was a member of the Spalding Gentlemen’s Society and the 48 Académie royale des sciences (Figure 1). Folkes became a friend of Voltaire, a participant 49 in French salon culture and a correspondent of one of its doyennes, Madame Geoffrin.2 50 Folkes was a governor of Coram’s Foundling Hospital, a patron of Hogarth and the first 51 member of the gentry to marry a London actress, one Lucretia Bradshaw; antiquary 52 William Stukeley related that Folkes’s mother Dorothy Hovell ‘grieved at it so much 53 that she threw her self out of a window and broke her arm’.3 Then again, Lucretia’s 54 debut play in the London Theatre was entitled The Royal Mischief, and Dorothy was 55 perhaps justifiably concerned with the family’s reputation, as her older sister 56 Etheldreda had married William Wake, who later became Archbishop of Canterbury. 57 Folkes was also deputy master of the Premier Grand Masonic Lodge of England and 58 active in the short-lived Egyptian Society. He was possibly the best-connected and 59 most versatile natural philosopher and antiquary of his age, an epitome of 60 Enlightenment sociability, yet he is today a surprisingly neglected figure. His was an 61 intellectually vibrant world in which the long shadow of Newton – Folkes’s patron 62 and hero – has tended to obscure those who followed him. 63 Folkes recorded the Italian leg of his peregrination from Padua to Rome in his 64 journal.4 His travel diary, like Folkes himself, is little known in the historical literature, 65 and, when it is assessed, it is to provide examples of historical topography or more 66 general commentary of the import of the Grand Tour, or analysed with regard to 67 Folkes’s interests in coins and medals.5 68 According to Stukeley, Folkes went on his journey because he was ‘baffled’ by his 69 losing the election for the Royal Society presidency to Sir Hans Sloane. And, indeed, 70 Folkes’s ‘vocal supporter and right-hand man, James Jurin … lost also his hard-won 71 Secretaryship’, handing over the society’s papers to his successor, William Rutty, on 7 72 December 1727.6 Stukeley’s opinion was, however, partisan. He was hostile to 73 74 in ce qui might have been forgotten by the author, in which case it could become Ce qui sera sera (‘whatever will 75 be, will be’). Folkes, however, was a near-native speaker of French. See also Lee Hartman, ‘“Que sera sera”: the 76 English roots of a pseudo-Spanish proverb’, Proverbium (2013) 30, pp. 51–104. My thanks to Charlotte 77 Marique for this explanation. 2 Harcourt Brown, ‘Madam Geoffrin and Martin Folkes: six new letters’, Modern Language Quarterly 78 (1940) 1–2, pp. 215–241. 79 3 The Family Memoirs of the Reverend William Stukeley, M.D., and the Antiquarian and other 80 Correspondence, vol. 1, Publications of the Surtees Society, vol. 73, Durham, London and Edinburgh: The 81 Surtees Society, 1882, p. 99. 4 Martin Folkes, ‘Journey from Venice to Rome’, MS Eng. misc. c. 444, op. cit. (1). His ‘Memoranda in case 82 he should go abroad again’ also indicates each stage of his journey and how many weeks he stayed in each 83 place, along with a list of his expenses. 84 5 John Ingamells, A Dictionary of British and Irish Travellers in Italy, 1701–1800: Compiled from the ‘ 85 Brinsley Ford Archive, New Haven, CT: Yale University Press, 1997, p. 365; William Eisler, The construction of the image of Martin Folkes (1690–1754): art, science and Masonic sociability in the age of 86 the Grand Tour’, The Medal 58 (Spring 2011), pp. 4–29. 87 6 David Haycock, William Stukeley: Science, Religion, and Archaeology in Eighteenth-Century England, 88 Martlesham: Boydell and Brewer, 2002, p. 52; Journal Book Original (1726–1731), JBO/14, f. 147, Royal Taking Newton on tour 3

89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 Fig. 1 - Colour online, B/W in print 118 119 Figure 1. The mezzotint copy by John Smith of Folkes’s portrait by Jonathan Richardson the 120 Elder. Folkes’s personal motto is inscribed on the bottom. British Museum, image: 121 1902,1011.4540AN121298001, Creative Commons BY-NC-SA 4.0 license. 122 123 Folkes’s irreligion, claiming that Folkes was ‘an errant infidel’ who ‘profess[ed] himself a 124 godfather to all monkeys’.7 Folkes certainly entertained materialist philosophies before 125 and after his tour of Italy; the Mancunian poet John Byrom recorded their conversation 126 when at Folkes’s house on Queen’s Square for dinner on 26 February 1725/6, to see his 127 ‘books and rarities’. They talked with the surgeon William Cheseldon and the 128 ‘ … 129 Society Library, London. As Haycock indicates, in spite of the general conviviality of its meetings [the Royal Society] was divided into two factions, broadly defined as the mathematical and the natural historical parties. 130 Their two chief representatives after Newton’s death in 1727 – Folkes and Sloane respectively – would come 131 head to head in a heated contest over who should succeed him as President’. Ibid., p. 52. 132 7 Family Memoirs of the Reverend William Stukeley, op. cit. (3), vol. 1, p. 14. 4 Anna Marie Roos

133 watchmaker George Graham about Mrs Folkes’s very comical pet monkey: they ‘dis- 134 Q2 puted whether he had reason or no’, concluding that ‘he was a man without reason’.8 135 Folkes entertained other puzzles from nature that gnawed at assumptions of God- 136 given human exceptionalism. In later correspondence with microscopist Henry Baker, 137 Folkes’s discussions centred around whether a parasitic twin could be ensouled.9 138 Their discussion was a result of Folkes’s second tour of France in May 1739, where 139 he met Madame Geoffrin, hostess of an illustrious Parisian salon, and where he was 140 exposed to Abraham Trembley’s work on the regeneration of hydra or polyps. As 141 Ratcliff has eruditely shown, work on polyps challenged the Aristotelian Chain of 142 Being, which had dominated understanding of the natural world and raised questions 143 of vitalism, materialism and deism.10 For instance, did the polyp have a soul, and 144 could that soul be split into two? Was the ability of the polyp to regenerate support 145 for preformation, the idea that all living things pre-existed as invisible germs? Folkes 146 and Baker asked similar questions about parasitic twins. 147 Stukeley’s ire was also probably raised because, when younger, he had been exposed 148 to heterodox notions from Folkes, who was then his close friend. Like Folkes, Stukeley 149 was an active Freemason when it was newly fashionable after the appointment of the 150 Duke of Montagu as grand master in 1721. Stukeley became a Mason of the 151 Salutation Tavern that year; by 1729, Stukeley admitted to Samuel Dale that he was 152 ‘in a manner voyd of religion’.11 Stukeley’s redemption and subsequent taking of holy 153 orders as a priest in the Church of England in 1729 may have made him uncomfortable 154 Q3 about his previous indiscretions.12 155 More practically, Folkes’s Grand Tour came five years after his loss of the Royal 156 Society election; in the interim, he had been appointed vice president by Sloane on 8 157 February 1733, so, contrary to Stukeley’s assertion, there must have been another 158 reason for his journey. Charles Weld in his 1848 History of the Royal Society claimed 159 that the journey was so that Folkes could ‘improve himself in classical antiquity’.13 160 Indeed, Charles Lennox, the 2nd Duke of Richmond (1701–1750), provided Folkes 161 with a number of rather blustery letters of introduction, one to Alessandro Albani, the 162 leading collector of antiquities in Rome, whom Lennox described as ‘a very odd Curr, 163 Ignorant enough, & proud as Hell’; Nevertheless, Lennox added he had ‘the finest 164 library, one of them, in Europe, & without exception one of the very best collection 165 of bustos, in the World. You must flatter him upon his learning’.14 Lennox also wrote 166 167 8 John Byrom, The Private Journal and Literary Remains of John Byrom, Manchester: Chetham Society, 168 1854–7, vol. 1, part 1, pp. 209–10. – 169 9 The correspondence of Henry Baker, vol. 1, ff. 218 219, John Rylands Library, University of Manchester. 10 Marc Ratcliff, The Quest for the Invisible: Microscopy in the Enlightenment, Aldershot: Ashgate, 2009. 170 11 Stukeley MS Eng. misc. e. 126 f. 83, Bodleian Library, Oxford. 171 12 George Kolbe, ‘Godfather to all monkeys: Martin Folkes and his 1756 library sale’, Asylum (April–June 172 2014), p. 41. Stukeley also may have been envious of the social position of Folkes, his man and neighbour, who 173 indirectly provided him with a living in London as vicar of St Georges in Queens Square via his uncle William Wake, an antiquarian, a numisticist and, as mentioned, the Archbishop of Canterbury. 174 13 Charles Weld, A History of the Royal Society, with Memoirs of the Presidents, London: J.W. Parker, 175 1848, 1: 480. 176 14 Charles Lennox to Martin Folkes, 31 July 1733, Royal Society MS/865/12. Taking Newton on tour 5

177 a letter of introduction for Folkes to Teresa Grillo Pamphili (d. 1763), the Genoese poet 178 who led an important literary salon (the Arcadia) in Rome. He referred to her rather 179 uncharitably as the ‘Ugliest Bitch, in the World, Damn’d proud also, & stark staring 180 mad, butt a Develish deal of Witt, some knowledge, & altogether Une Maitresse 181 ferme, sans un brin de religion [a resolute woman without a touch of religion]’.15 182 In a more serious vein, James Jurin wrote a letter for Folkes to Giovanni Poleni, the 183 Italian natural philosopher and expert in architecture and classical antiquity (who had 184 also been engaged in the vis viva dispute with Samuel Clarke and other Newtonians). 185 Jurin stressed that 186 Folkes was an excellent gentleman of high achievement in every kind of literature, especially 187 physics and mathematics; whom Newton valued so highly that, nor content to consider him 188 worthy of his own close friendship, he voluntarily chose him to carry out the duties of Vice- 189 President at the formal meetings of the Society in his own absence.16 190 Folkes subsequently met Poleni in Venice on 18 July 1733, on which occasion he dis- 191 cussed meteorology and the state of learning in England.17 192 Intellectual and aesthetic development was thus part of the reason for Folkes’s tour, 193 just as before him it had been for natural philosopher George Berkeley, who, in his 194 case, cultivated a taste for Greek Doric architecture. In 1713, Berkeley wrote to Sir 195 John Percival stating that he was interested in the ‘agreeable effects’ of such buildings 196 on his eyes, an interesting remark given that Berkeley had recently published his New 197 Theory of Vision (1709), a subjectivist theory of perception.18 198 Like Berkeley, Folkes melded aesthetic and natural-philosophical concerns, his tour 199 one of scientific peregrination, or ‘science on the move’, that was prevalent from 1650 200 to 1750.19 The origins of the scientific peregrination were in the ‘peregrinatio academia 201 of early modern aspiring scholars’; another predecessor was the peregrinatio medica,as 202 medicine was the subject for which foreign travel was most valuable.20 Medical students 203 brought back new techniques, knowledge and materia medica to their homeland; in the 204 205 15 Charles Lennox to Martin Folkes, 31 July 1733, Royal Society MS/865/12. The letter itself to Pamphili is 206 Royal Society MS/865/13. For the Arcadia and Pamphili’s role as host see Elisabetta Graziosi, ‘Women and 207 academies in eighteenth-century Italy’, in Paula Findlen, Wendy Wassyng Roworth and Catherine M. Siena 208 (eds.), Italy’s Eighteenth Century: Gender and Culture in the Age of the Grand Tour, Stanford: Stanford – 209 University Press, 2009, pp. 103 119. 16 For the letter of introduction see The Correspondence of James Jurin (1684–1750), Physician and 210 Secretary to the Royal Society (ed. Andrea Rusnock), Amsterdam: Rodolpi, 1996, p. 391. The vis viva 211 dispute lasted from 1686 until the 1720s and concerned whether the vis viva or momentum was conserved 212 in the universe. The dispute started between Descartes and Leibniz and resulted over confusion of 2 ‘ ’ 213 momentum (mv) and kinetic energy (1/2mv ). See Carolyn Iltis, Leibniz and the vis viva controversy , Isis (Spring 1671) 62(1), pp. 21–35. 214 17 Folkes, ‘Journey from Venice to Rome’, op. cit. (1), f. 25r. 215 18 Edward Chaney, The Evolution of the Grand Tour: Anglo-Italian Cultural Relations since the 216 Renaissance, London and Portland: Frank Cass, 1998, p. 328. ‘ 217 19 Mark Greengrass, Daisy Hildyard, Christopher D. Preston and Paul J. Smith, Science on the move: Francis Willughby’s expeditions’, in Tim Birkhead (ed.), Virtuoso by Nature: The Scientific World of 218 Francis Willughby FRS (1635–1672), Leiden: Brill, 2016, pp. 142–226, 145. 219 20 Zur Shalev, ‘The travel notebooks of John Greaves’, in Alistair Hamilton, Maurits H. Van Den Boogert 220 and Bart Westerweel (eds.), The Republic of Letters and the Levant, Leiden: Brill, 2005, pp. 77–103, 85. See 6 Anna Marie Roos

221 1670s, Thomas Bartholin, when recalling his own peregrinatio medica, noted, ‘Today 222 there are many travellers; indeed, it seems as if the whole of Europe is on the move’.21 223 Young medical students would travel abroad not only to earn professional credentials, 224 but also to attain accomplishments, becoming gentlemen of quality and adding polish to 225 their English education. But by the time of Folkes’s journey, I would argue, scientific 226 tours apart from the reasons of politesse and medical pedagogy had long developed as 227 a separate enterprise. Previous works such as botanist John Ray’s later published trav- 228 elogue of his journey on the Continent (editions in 1693 and 1738) reinforced the 229 image of ‘diligent natural philosophers, engaged in the pursuit of activities conducive 230 to the public [and scientific] good’.22 In 1698, physician and naturalist Martin Lister 231 (1639–1712) wrote a guidebook of his Journey to Paris, intending it specifically to 232 appeal to fellow natural philosophers.23 Lister directed the reader to his interests in 233 natural history using his mature judgement and own eyes, offering ‘clean Matter of 234 Fact, and some short notes of an unprejudiced Observer’.24 235 Although not a doctor or a naturalist like Lister or Ray, Folkes had similar sentiments 236 reflecting his specialism in mathematics and his interest in architectural measurement; his 237 journey was designed to answer particular questions of natural philosophy. His diary 238 reflected ‘antiquarian science’, a form of peregrination in which he used metrology to 239 understand not only the aesthetics but also the engineering principles of antique buildings 240 and artefacts, as well as their context and place in the Italian landscape. Although Folkes 241 followed in the tradition of past natural philosophers such as John Greaves, the Savilian 242 Professor of Astronomy who desired to standardize and synchronize the weights and 243 measures of all ancient and modern nations, we will see in the first part of the paper 244 that Folkes also wished to verify Greaves’s measurements of the Roman foot as an expres- 245 sion of his status as a Freemason and in response to interests promoted within the Society 246 of Antiquaries.25 Using Folkes’s diary, his account book of his journey in the Norwich 247 archives and accompanying correspondence with other natural philosophers such as 248 Francesco Algarotti (1712–1764), Anders Celsius (1701–1744) and Abbé Antonio 249 Schinella Conti (1667–1749), we will then determine to what extent this journey estab- 250 lished Folkes’s reputation as an international broker of Newtonianism, particularly in 251 optics. We will then analyse Folkes’s subsequent application of his mentor Newton’s 252 natural philosophy to geodesy, the ultimate form of metrology. Finally, we will determine 253 to what extent Folkes was successful in demonstrating the overall primacy of English sci- 254 entific instrumentation to Italian virtuosi. His journey was an expression of the motto 255 scrawled in his diary, symbolic of who and what he would become. 256 257 Ole Peter Grell and Andrew Cunningham (eds.), Centres of Medical Excellence? Medical Travel and Education in Europe, 1500–1789, Aldershot: Ashgate, 2010. 258 21 Thomas Bartholin, On the Burning of His Library and on Medical Travel (tr. C.D. O’Malley), Lawrence: 259 University of Kansas Libaries, 1961, p. 50. 260 22 Greengrass et al., op. cit. (19), p. 152. 261 23 Martin Lister, A Journey to Paris in the Year 1698 (ed. Raymond Phineas Stearns), Urbana, Chicago and London: University of Illinois Press, 1967, p. 2. 262 24 Lister, op. cit. (23), p. 3. 263 25 Zur Shalev, ‘Measurer of all things: John Greaves (1602–1652), the Great Pyramid, and early modern 264 metrology’, Journal of the History of Ideas (October 2001) 63(4), pp. 555–575. Taking Newton on tour 7

265 Folkes, his diary, Freemasonry and metrology 266 In her discussion of early eighteenth-century arguments between materialists and 267 anti-materialists, and of the formal foundation of modern Freemasonry with the estab- 268 lishment of the Grand Lodge in London in 1717, Margaret Jacob has suggested that ‘tol- 269 erant-minded Newtonians … invented a new form of ritual to worship the Grand 270 Architect of the Universe’; Jacobs argued, in short, that Freemasonry was an innovation 271 sprung ‘from Newtonian inspiration’.26 Garry Trompf agreed, writing, ‘The more one 272 ponders Newton’s axial principles … and then one relates this covert, Talmudically- 273 Q4 inspired unorthodoxy to his fascination for the mysterious proportions of the 274 Solomonic temple, the more one can sense the milieu of early Freemasonry.’27 Folkes 275 was not only a ‘prestigious figure in the scientific and antiquarian communities’ in 276 Britain and the Continent, but also a visible ambassador of Freemasonry’s ideals of 277 free thought and sociability, and of Newtonian scientific principles. It was rumoured, 278 after Folkes returned from Italy, that he was the author of the scurrilous Relation 279 Apologique (1738) for Freemasonry which applied Newtonian principles to government 280 and communicated Masonry as a primarily scientific institution.28 281 Folkes was a follower of speculative Freemasonry, a non-sectarian group of freethin- 282 kers to which many fellows of the Society of Antiquaries and the Royal Society belonged; 283 Q5 forty-five percent of the fellows of the Royal Society were Masons in the 1720s.29 284 Between 1719 and 1742, he proposed eleven fellow Masons of the Bedford Head and 285 Maid’s Head Lodge in Norfolk (which he founded) as fellows of the Royal Society.30 286 Folkes’s friend and patron, Charles Lennox, was grand master of the Bedford Head 287 Lodge (installed in 1724/5), and a fellow of the Royal Society. Folkes also provided 288 Lennox with antiquarian documents about Freemasonry; Lennox wrote to Folkes in 289 1725 apologizing for missing the Masonic feast day of St John’s, ‘guilty of such an omis- 290 sion that nobody less than the Deputy Grand Master of Masonry can make up for me’. 291 He then proceeded, ‘I thanke you for the Old Record you sent me, it is really very 292 Q6 curious, & a certain proof at least, or our antiquity, to the unbelievers’.31 293 Although the precise line that divided deism, natural religion and the revealed religion 294 of the orthodox Christian was subtle in this period, Folkes’s travel diary to Italy con- 295 firmed his freethinking beliefs. He noted that he considered Catholicism and 296 297 26 David Boyd Haycock, William Stukeley: Science, Religion and Archaeology in Eighteenth-Century 298 England, The Newton Project, at www.newtonproject.ox.ac.uk/view/texts/normalized/OTHE00017; Betty 299 Jo Teeter Dobbs and Margaret C. Jacob, Newton and the Culture of Newtonianism, Amherst: Humanity 300 Books, 1995, p. 102. ‘ ’ 301 27 Garry W. Trompf, On Newtonian history , in Stephen Gaukroger (ed.), The Uses of Antiquity: The Scientific Revolution and the Classical Tradition, New York: Springer, 2013, pp. 213–249, 234–235. 302 28 William Eisler, ‘The construction of the image of Martin Folkes’, The Medal (2011) 58, pp. 1–29, 5; see 303 also Andreas Önnerfos, ‘The earliest account of Swedish Freemasonry? Relation apologique (1738) revisited’, 304 Ars Quatuor Coronatorum (2014) 127, pp. 1–34. ‘ “ ” 305 29 Paul Elliot and Stephen Daniels, The school of true, useful and universal science ? Free masonry, natural philosophy and scientific culture in eighteenth-century England’, BJHS (June 2006) 39(2), pp. 217– 306 229, 213. 307 30 Ric Berman, The Foundations of Modern Freemasonry, Brighton: Sussex University Press, 2012, p. 108. 308 31 Charles Lennox to Martin Folkes, 27 June 1725, Royal Society MS/865/1. 8 Anna Marie Roos

309 Protestantism ‘as only a tool of the state to keep the vulgar in awe’, noting that Venetian 310 intellectuals were ‘fond of any sort of freethinking book, and with what eagerness they 311 speak on the subject and enquire after the ways of thinking of a nation more used to 312 liberty of thought than themselves’.32 That said, Folkes did go on to find them 313 wanting in the knowledge of religion: 314 The bible is in no ways known and I have met with stupendous instances of mistakes about the 315 things contained in it … and it has been with the greatest surprise several have heard me speak 316 of the measure of learning of all sorts that very antient … book contains.33 317 318 Martin Folkes considered the Bible an authoritative historical source (one of many), and ’ 319 even helped Thomas Pellet edit a manuscript of Newton s Biblical Chronology of ‘ ’ ’ 320 Ancient Kingdoms, a truncated version of Newton s more radical manuscript , as histor- 34 321 ian James Force has called it. Newton used data about the precession of the equinoxes ’ 322 to formulate his new chronology, and Folkes s astronomical expertise was useful in this 323 regard. Folkes, however, unlike Newton, did not identify with the use of astronomical ‘ 324 data to vindicate religious truths, admitting to his friend John Byrom that he was a ’ 35 325 heretic about the book of Daniel . Nor was Folkes a believer in natural theology, ’ – 326 also admitting to Byrom that he thought William Derham s Astro Theology, a corollary 327 to the Boyle Lectures that used natural history and teleology to promote and prove a ‘ ’ 36 328 natural theology, a silly book . It seemed an appropriate comment for someone 329 with such a resolutely non-teleological personal motto. 330 As a Freemason, Folkes was, however, interested in using biblical evidence in other 331 ways. He wished to clarify the scripturally ambiguous dimensions of the sacred cubit ’ 332 of the Hebrews used to build Solomon s Temple and to assess the dimensions of the 37 333 Roman foot. Folkes took as his motto in the album amicorum (friendship book) for ‘ ’ ‘ 334 the Egyptian Society omnia in mensura et numero et pondere diposuisti ,or thou has ’ ’ 335 ordered all things in measure and number and weight (Wisdom, 11:21) . Folkes s inter- fl 336 ests re ected the current intellectual milieu, as masonry emphasized a mathematical deity ’ ‘ 337 Q7 that, in Eliot and Daniels s phrase, accorded well with the Newtonian conception of the ’ 38 338 universe, with a grand mathematician or architect at the centre . Newton had previ- 339 ously written a dissertation upon the sacred cubit which would be republished in 340 ‘ ’ 341 32 Folkes, Journey from Venice to Rome , op. cit. (1), f. 24r. 33 Folkes, ‘Journey from Venice to Rome’, op. cit. (1), f. 24r. 342 34 James E. Force, William Whiston: Honest Newtonian, Cambridge: Cambridge University Press, 2002, 343 p. 136. 344 35 Byrom, op. cit. (8), vol. 2, part 1, p. 27, entry for 30 March 1736. 345 36 Byrom, op. cit. (8), vol. 1, part 1, p. 180, entry for 14 December 1725. 37 The specification of the cubit was ambiguous: ‘in the man’s hand a measuring reed six cubits long, of a 346 cubit and a handbreadth each: so he measured the thickness of the building, one reed; and the height, one reed’ 347 (Ezekiel 40:5). The Hebrew text reads: ‘a measuring reed, six cubits by the cubit and a handbreadth’. ‘It was 348 unclear whether the six cubits marked on the reed were particularly large, each outsizing the regular cubit by a 349 handbreadth; or whether the reed as a whole measured six cubits and one extra handbreadth. This was to become one of the key problems of much Temple scholarship’. See Jetze Touber, ‘Applying the right 350 measure: architecture and philology in biblical scholarship in the Dutch early Enlightenment’, Historical 351 Journal (2015) 58(4), pp. 959–985, 964. 352 38 Elliot and Daniels, op. cit. (29), p. 220. Taking Newton on tour 9

353 1737, along with the works of John Greaves by antiquary Thomas Birch, who wrote the 354 History of the Royal Society (1757). Moreover, as Haycock noted, in 1723, Bernard 355 Lamy published his Apparatus Biblicus with engravings of the Tabernacle and 356 Temple, and in 1726 William Whiston advertised ‘a small, but curious Course of 357 Lectures’ on astronomical subjects which also included ‘Sacred Architecture past’,as 358 well as ‘Sacred Architecture Future’.39 Freemasonry was taking off in London at this 359 time, with prominent Newtonians playing an active role. 360 Therefore it is not surprising that one Folkes’s first tasks when he arrived in Venice 361 was to measure the height of the Campanile by its shadow, concluding that it was 362 140 feet high. He then measured again to confirm his conclusions; to do this, Folkes 363 figured out the conversion factor between Venetian palms and English feet. He then pro- 364 ceeded to measure the Rialto bridge in Venice to confirm his determination and compari- 365 son of past standards of measurement. Folkes noted on 8 July 1733 that, ‘writers not 366 agreeing perfectly with one another’ about the Rialto’s dimensions, he decided to 367 measure it himself using ‘packthread and a plumb bob’; he made a sketch in his diary 368 of the bridge recording his observations.40 He carefully compared his own measures 369 of the Rialto to those of it taken by Francesco Sansovino, the son of Jacopo 370 Sansovino (1486–1570). Jacopo was the proto or chief architect of Venice who was 371 responsible for the rebuilding of the Fabbriche Nuove di Rialto complex (seat of the 372 magistrates in charge of customs and duty).41 Disturbed that his measurements of the 373 bridge were different from Sansovino’s, he wrote, 374 I would readily think may be partly owing to defect in my own measure, partly perhaps an 375 inaccuracy in the building the bridg[e] itself to the intended model, and perhaps again in the 376 not having to perfect these proportions between the English and Venetian foot.42 377 378 After making some enquiries after the original standard of the Venetian measures, which ‘ ’ 379 he found to be fruitless, he took some measures of St Geminiano s Church in order to ’ 380 have made something out by them . However, upon comparing the measures he had ‘ 381 taken, Folkes found the church was not built by the Venetian foot but by the Roman ’ 43 382 Architectonick palm whose length comes out very exactly by it . 383 It was a perceptive comment. St Geminiano was in the Piazza San Marco, part of the 384 complete remodelling of the piazza and surrounding buildings by Sansovino in 385 Renaissance Venice in the classical style; as historian Fiona Kisby has noted, the ‘ 386 effect was to superimpose an evocation of ancient Rome on the existing Byzantine ele- ’ 44 387 ments . St Geminiano, directly across the piazza from San Marco, was a focal point of 388 389 39 Haycock, op. cit. (26). 40 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 20r. 390 41 Folkes referred to Francesco Sansovino, Venetia, città nobilissima, et singolare: Descritta in XIIII. Libri, 391 Venetia, 1663, p. 365. 392 42 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 20r. ‘ ’ 393 43 Folkes, Journey from Venice to Rome op. cit. (1), f. 26r. Folkes also routinely complained in his journal that finding exact calculations for traditional Venetian measures was difficult. 394 44 Fiona Kisby, Music and Musicians in Renaisance Cities and Towns, Cambridge: Cambridge University 395 Press, 2005, p. 31; See also Deborah Howard, Jacopo Sansovino: Architecture and Patronage in Renaissance 396 Venice, New Haven, CT and London: Yale University Press, 1975. 10 Anna Marie Roos

397 the architectural complex designed by Jacopo Sansovino in Vitruvian proportion to 398 evoke the ancient Roman forum (Figure 2). Hence Folkes suspected and proved that 399 Sansovino used Roman measurements to create his building, particularly as Vitruvius 400 in his third book of De Architectura gave a thorough description of the Roman foot 401 or pes and palms (one-quarter of the foot).45 In this manner, principles of measure 402 and geometry would ensure harmony and aesthetic appeal in the building’s design. In 403 other words, Folkes was investigating architectural metrology to provide what we 404 would term archaeological information about architects and builders of Renaissance 405 Venice, and, as we will see, ancient Rome. 406 Queries about ancient metrology began in 1573 with the publication of De Mensuris 407 et ponderibus Romanis et Graecis by Lucas Paetus. That publication spawned an active 408 debate about the exact length of the pes. Dissatisfied with inconsistencies in textual evi- 409 dence, John Greaves, professor of astronomy at Oxford, visited Rome in 1639, to 410 ‘examine as many ancient measures, and monuments, in Italy, and other parts, as it 411 was possible’, and to compare these ‘with as many Standards, and Originals, as I 412 procure the sight of’.46 He thus measured brass measuring rods in Roman ruins, and 413 the foot measures on the tomb of Titus Statilius Aper and the statue of Cossutius. 414 Greaves then noted with some pleasure that these foot measures exactly corresponded 415 with the distance between the milestones on the Appian Way.47 He then made compar- 416 isons between the Roman foot and the iron standard of the English foot in the London 417 Guildhall and published his findings on Discourse on the Romane foot and denarius in 418 1647, concluding that the Cossutian foot was the ‘true’ Roman pes. Greaves also 419 claimed that he thought he could find a relationship between the pes and the sacred 420 cubit, something which Newton also noted in his own treatise on the cubit. 421 Folkes followed the same methodology as Greaves in his own travels. In 1736, Folkes 422 identified the Root Canonical Greek foot as 1.0057142 times the English measure, and 423 the Roman pes as 0.966 of the English foot, noting them as being engraved on a stan- 424 dards stone tablet at the Roman Capitol that might have been the actual record of the 425 pes monetalis. His paper about the stone was subsequently published in the 426 Philosophical Transactions of the Royal Society; Folkes recorded ‘setting the point of 427 my Compasses’ in the lines in the stone that represented the measures, and also noted 428 his ‘chief Attention was given to the Roman foot, as of greater Consequence than the 429 other measures’.48 430 In making his conclusion, Folkes considered previous measurements made by Fabretti, 431 but recorded in his diary that he also measured the height of the Trajan Pillar ‘using an 432 ‘ 433 45 For when two palms are taken from the cubit, there is left a foot of four palms, and the palm has four fingers. So it comes that the foot has sixteen fingers, and the bronze denarius as many asses.’ (‘E cubito cum 434 dempti sunt palmi dueo, relinquitur pes quattuor palmorum, palmus autem habet quatuor digitos. Ita 435 efficitur uti pes habeat XVI digitos, et totidem asses aereos denarius’). Virtruvius, On Architecture, in two 436 volumes (tr. Frank Granger), London: William Heinemann, Ltd, vol. 1, Book III, c. I, pp. 164–165. 437 46 John Greaves, A Discourse of the Romane Foot, and Denarius: from when, as from two principles, the Measures, and Weights, used by the Ancients, may be deduced, London: M.F, 1647, p. 20. 438 47 Greaves, op. cit. (46), pp. 20, 23. 439 48 Martin Folkes, ‘An account of the standard measures preserved in the Capitol at Rome’, Philosophical 440 Transactions (1735/6) 39, pp. 262–266, 262–263. Taking Newton on tour 11

441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457

458 Fig. 2 - Colour online, B/W in print 459 Figure 2. Piazza San Marco, etching by Canaletto, 1710–1758, Rijksmuseum, Amsterdam, public 460 domain, object number RP-P-OB-35.577. St Geminiano, indicated by the arrow, was the focal 461 point of the piazza which evoked the Roman past. 462 463 exact two-foot rule brought from London’. Folkes was particularly interested in the 464 column because the height of its shaft from the plinth of the base to the abacus of the 465 Q8 column was said to measure exactly one hundred Roman feet, a columna centenaria.49 466 The column was thus ideal to determine the dimensions of the Roman foot.50 Now, of 467 course, studies of metrology and measurement surveys of ancient buildings constitute 468 Q9 some of the most important work in archaeology.51 He found the column, ‘from the 469 Ground to the Top of the Cimatium of the Capitol’,tobe‘115 feet 10 inches 5/8’; 470 this height, divided by 120, gave nearly 966 for the quotient, thus confirming that the 471 Roman foot was 0.966 of an English foot and used frequently in Roman architecture. 472 Ironically, Folkes’s exactitude of measurement has not been borne out in modern 473 studies as there appear to be some slight variations in the Roman pes. Historians 474 Soren and Soren attribute these variations to ‘the Augustan decree to standardise 475 Roman metrology … most easily implemented by the transport of replicas of the pes 476 monetalis at Rome to the colonies’.52 477 During his tour, Folkes also discussed his work on the Trajan Column in more depth 478 with the Venetian Francesco Algarotti. Folkes was interested in measuring the figures on 479 480 49 G. Boni, ‘Trajan’s Column’, Proceedings of the British Academy (1907) 3(1–6), p. 3. 481 50 Folkes, op. cit. (48), p. 266. Raphaelis Fabretti, De Columna Traiani, Rome: Nicolai Angeli Tinassij, 1693. 482 51 David Soren and Noelle Soren, A Roman Villa and a Late Roman Infant Cemetary: Excavation at Poggio 483 Gramignona, Rome: L’ Erma di Bretscheider, 1999, p. 182. 484 52 Soren and Soren, op. cit. (51), p. 189. 12 Anna Marie Roos

485 the column to assess and compare the Roman artist’s use of visual perspective as opposed 486 to the use of perspective in modern artistic practice.53 Their conversation comparing 487 ancient and modern techniques was an extension of the literary quarrel of the ‘ancients 488 and moderns’ that raged amongst French and English intellectuals in the seventeenth and 489 early eighteenth centures. Intellectuals who sided with the ‘ancients’ argued that antique 490 literature offered the sole models for literary excellence; the ‘moderns’, on the other 491 hand, challenged the supposed supremacy of the classical writers. This scholarly 492 debate was extended to assessing technological and aesthetic achievement.54 Folkes 493 was particularly interested in discussing with Algarotti to what extent measurement 494 could answer questions about the relative merits of ancient technology and artistic 495 production. 496 Q10 Algarotti had associated himself with ‘radical conversazioni and early masonic lodges’ 497 at some point during his tours of Padua and the Veneto, and subsequently in Florence 498 Q11 and Rome of the early 1730s, where he met Folkes.55 Algarotti was best known for 499 his popularization of Newton’s precepts in his Il Newtonianismo per le dame, but he 500 also wrote a number of letters and essays on aesthetics, including one in which he ana- 501 lysed the helical frieze on Trajan’s column. In a letter to Jean Paolucci, Algarotti recalled 502 that he speculated with Folkes as to whether the bas relief on the Trajan Column gave 503 them any reason to presume that the ancients did not have any knowledge of the ‘pro- 504 portions of perspective’.56 Folkes noted in an article he later published about the 505 column that 506 it has been said by some, that the bas-reliefs on the shaft of this pillar increase in size upwards, 507 in order to appear of the same size below; but this is not true; and I had an opportunity of sat- 508 isfying myself from the plaister-cast of the whole pillar, kept at the French academy of painting 509 and sculpture in Rome, where … I measured several of the fairest figures.57 510 It appeared from Folkes’s observations of the column that the Roman artists who carved 511 frieze on the column did not use traditional perspectival techniques in their portrayal of 512 the Dacian Wars. 513 Algarotti also recalled discussing with Folkes the arguments of Charles Perrault, who 514 rose in the French Academy to champion modern authors in the quarrel between the 515 ancients and moderns. Folkes and Algarotti noted that Perrault was of the opinion 516 that while the ancients excelled in sculpture (a genre that in Perrault’s eyes demanded 517 518 53 Francesco Algarotti to Jean Paolucci, 20 May 1763, in Oeuvres de comte Algarotti traduit de l’italien, 519 vol. 6, Berlin: G.J. Decker, 1772, pp. 208–214. 520 54 Excellent analyses of the ancients-versus-moderns debate may be found in Joan DeJean, Ancients against 521 Moderns: Culture Wars and the Making of a Fin de Siècle, Chicago, The University of Chicago Press, 1997; Joseph M. Levine, The Battle of the Books: History and Literature in the Augustan Age, Ithaca, NY: 522 Cornell University Press, 1991. 523 55 Massimo Mazzotti, ‘Newton for ladies: gentility, gender and radical culture’, BJHS (June 2004), pp. 119– 524 146, 143. ‘ ’ ’ 525 56 Francesco Algarotti, Dialoghi Sopra l Ottica Neutoniana ,inOpere Varie Del Conte Francesco Algarotti, vol. 1, Venice: Giambiatista Pasquali, 1757, p. 317. 526 57 Martin Folkes, ‘On the Trajan and Antonine Pillars at Rome’, Read 5 Feburary 1735–6, Archaeologia 527 (January 1779) 1–2, pp. 117–121, 120. Contrary to Folkes, the bas relief figures actually do slightly 528 increase from sixty to eighty centimetres in height. Taking Newton on tour 13

529 little ‘reflection’ and abstract thought), bas-reliefs and painting required a deeper under- 530 standing of perspective and spatial relations which the ancients did not have. Perrault 531 thought his opinion was supported by the ‘casts of the Trajan Column’ he saw in 532 Paris, which to him were naive in their understanding of perspective space.58 533 However, Folkes and Perrault were sceptical about Perrault’s claim, Algarotti writing 534 that ‘the defects which are believed to been seen in the ancient bas-reliefs, and especially 535 in the Trajan Column, prove nothing against the knowledge of the ancients in regard to 536 perspective’. Rather, Algarotti and Folkes realized the artists who carved the column 537 used fewer emblematic forms to represent the events of the war rather than hundreds 538 of individual participants; perspectival tricks could not assist the artist in highlighting 539 ‘certain figures, groups, or parts of the composition’. Indeed, the composition in the 540 frieze is characterized by diagonals so that the ‘figure of the emperor is emphasized 541 along with the direction of gazes and actions of the figures surrounding him’.59 To 542 make the figures and iconography intelligible to a spectator who was at a great distance, 543 the composition required a multiperspectival approach and simple converging and diver- 544 ging orthogonals were not appropriate. Trajan’s Column was in fact designed so that 545 viewers could comprehend the story of the Dacian Wars from bottom to top standing 546 in one place rather than circling the column twenty-three times as the carved spiral 547 frieze does. A viewer could see key events of the war from two main vantage points.60 548 Folkes and Algarotti thus concluded that far from being naive, the designer of the 549 column’s frieze was more like a great captain employing a stratagem of sophistication. 550 551 Folkes, Venice and Newtonianism 552 553 Folkes’s conversation with Algarotti reflected his pervasive interest in optics, optical illu- 554 sion and perception, topics which came to the fore when he was in Venice. Although the 555 Venetians were aware of the theories of Newtonian optics, in the 1730s there was a 556 degree of scepticism among natural philosophers there about the validity of the refran- 557 gibility of light in the visible spectrum. As a result, when he was in the Veneto, Folkes 558 cultivated fellow mathematicians and astronomers to gain adherents of the Newtonian 559 research programme in the Royal Society. 560 561 562 58 Charles Perrault, Paralelle Des Anciens et Les Modernes En Ce Qui Regarde L’Eloquence, Paris: 563 J. B. Coignard, 1688–1697, vol. 1, pp. 190, 193–194: ‘Il n’y a aucune perspective ny aucune degradation … 564 Les figures sont presque toutes sur a mesme ligne; s’il y en a quelques-unes sur le dierriere, ells sont aussi ’ 565 grandes et marquees que celles qui sont sur le devant; en sorte qu elles semblent este montées sur des Gradins pour se faire voir les unes au dessus des autres’. See also Larry F. Norman, The Shock of the 566 Ancient: Literature and History in Early Modern France, Chicago: The University of Chicago Press, 2011, 567 p. 235 n. 10; and Anne Betty Weinshanker, Falconet, His Writings and His Friend Diderot, Geneva: 568 Librairie Droz, 1966, p. 89. 569 59 Tina Bawden, Dominik Bonatz, Nikolaus Dietrich, Johanna Fabricius, Karin Gludovatz, Susanne Muth, Thomas Poiss and Daniel A. Werning, ‘Early visual cultures and Panofsky’s perspektive als “symoblische 570 Form”’, eTopoi: Journal for Ancient Studies (2016) 6, pp. 525–570, 551. 571 60 ‘Reading Trajan’s Column’, National Geographic,atwww.nationalgeographic.com/trajan-column, 572 accessed 20 May 2017. 14 Anna Marie Roos

573 Before he left for his journey and during his time on the Council of the Royal Society, 574 Folkes was exposed to a constant stream of accounts ‘of the present state of Learning 575 and Experimental Philosophy in Italy’, from the English Jacobite Thomas Dereham, 576 the Royal Society’s contact in Florence. Dereham was the translator into Italian of 577 Astro-Theology,afive-volume set of the Philosophical Transactions of the Royal 578 Society (published by Felice Mosca between 1729 and 1734), as well as a work by 579 Newtonian physician George Cheyne.61 Dereham relied on luminaries such as 580 Eustachio Manfredi, the chair of mathematics in Bologna, discoverer of a comet and 581 asteroid, and observer of the transit of Mercury, for natural-philosophical news to 582 pass on to the Royal Society; Manfredi was a correspondent of Algarotti and also 583 passed along news of Venetian natural philosophy.62 584 Venice, in particular, was also a favourite haunt of Newtonian mathematicians and 585 their intellectual circles, and Folkes went there to convince their virtuosi of the truth 586 of Newton’s work in optics. Twenty years previously Newtonians had fought a cam- 587 paign against Italian supporters of Leibniz in the calculus dispute. In Padua and 588 Venice, after 1710, Jakob Hermann and Nicolas Bernoulli were ‘promoters of a fierce 589 campaign against Newton’s methods of fluxions in the calculus’.63 Hermann had 590 taught differential and integral calculus using Leibniz’s method at Padua from 1707 591 to 1713. However, Newton had friends as well, and hoped to diminish the prestige of 592 Leibniz through the offices of Abbé Antonio Schinella Conti, who was born and edu- 593 cated in the Veneto but spent several years abroad before returning to Venice in 1726. 594 Conti was in London between 1715 and 1718 to become part of Newton’s intellectual 595 circle, where he met Folkes. In his travel diary of 1733 Folkes noted, ‘I had known the 596 Abbé very well in England above 16 years ago, I had a very agreeable conversation with 597 him as he is a Gentleman of great knowledg and politeness, and indeed the most knowing 598 man of all the Italians of his side the country’.64 Conti would also serve as a go-between 599 for Leibniz and Newton in the calculus affair, and, through Conti’soffices, Newton 600 thought he could lessen Leibniz’s prestige in Italy, which had grown during the calculus 601 dispute.65 602 Folkes had also been tutored by Abraham De Moivre (1667–1754), his correspond- 603 ence showing that he and Edward Montagu dined with their former teacher on de 604 Moivre’s eightieth birthday in 1747.66 De Moivre would subsequently be an intermedi- 605 ary in a mathematical dispute between Newton and Bernoulli, so Folkes was intimately 606 au fait with the history of the Newton Wars. 607 608 61 Journal Book Original 14 (1726–1731), JBO 14, 19 January 1726, p. 37, Royal Society Library, London; ’ 609 Harold Samuel Stone, Vico s Cultural History: The Production and Transmission of Ideas in Naples, Leiden: Brill, 1997, pp. 278–280. 610 62 Journal Book Original 14 (1726–1731), JBO 14, 21 March 1727, p. 199, Royal Society Library, London. 611 63 Paolo Casini, ‘The reception of Newton’s Opticks in Italy’, in J.V. Field and Frank A.J.L. James (eds.), 612 Renaissance and Revolution: Humanists, Scholars, Craftsmen and Natural Philosophers in Early Modern – 613 Europe, Cambridge: Cambridge University Press, 1997, pp. 215 229, 217. 64 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 37r. 614 65 Casini, op. cit. (63), p. 217. 615 66 ‘Folkes to Stirling, 10 June 1747’, in C. Tweedie, James Stirling: A Sketch of This Life and Works along 616 with This Scientific Correspondence, Oxford: Oxford University Press, 1922, p. 192. Taking Newton on tour 15

617 Before his journey, Folkes had attended a series of Royal Society meetings in which the 618 society responded to the refutation of Newton’s optical work by Giovanni Rizzetti 619 (1675–1751), a Paduan nobleman who belonged to the circle of the mathematician 620 Jacopo Riccati (1676–1754) of Castlefranco Veneto. The Royal Society journal book 621 for 27 June 1728 reported that the society received Rizzetti’s De Luminis 622 Affectionibus Specimen Physico Mathematicum; the tract was referred ‘to Dr 623 Desaguliers which he promised to make an extract of’.67 In De Luminis, Rizzetti dis- 624 cussed refrangibility, the degree to which light refracts passing from one medium into 625 another, or, as Newton wrote, a ‘predisposition, which every particular Ray hath to 626 suffer a particular degree of Refraction’.68 In particular, Rizzetti claimed he could not 627 replicate the experiments in Book 1 of the Opticks, in which Newton used a candle to 628 illuminate a two-coloured card with black silk threads wrapped around it, thus sup- 629 posedly demonstrating the principle of chromatic aberration.69 630 Newton had placed a glass lens at a distance of six feet from the card, and used it to 631 project the light coming from the illuminated card onto a piece of white paper which was 632 at the same distance from the lens on the other side. He moved the piece of white paper 633 back and forth, taking note where and when the red and blue parts of the image were 634 most distinct. The black threads indicated distinctness of the image (when the lines 635 created by the thread were sharpest). Newton found it ‘impossible to focus the image 636 of black silk-thread lines upon a blue background at the same distance as when the 637 same lines are placed against a red background; the distance between the two positions 638 of sharp focus was as much as one and half inches’.70 In other words, to get a distinct red 639 image, the paper had to be held 1.5 inches further away than it was to obtain a distinct 640 blue image. Newton thus concluded that the blue light was refracted more by the lens 641 than the red, and was more refrangible.71 642 Red and blue light were not strictly homogeneous, and so not all the blue light was 643 more refrangible than all the red light, something Newton admitted. However, he indi- 644 cated that this experiment demonstrated a general effect: ‘But these Rays, in proportion 645 to the whole Light, are but few, and serve to diminish the Event of the Experiment, but 646 are not able to destroy it’.72 Newton thus described an ideal experiment. 647 The inability to create these ideal conditions was the point upon which Rizzetti had 648 seized. The popular lecturer John Theophilus Desaguliers (1683–1744) refuted 649 Rizzetti’s claims in a series of optical experiments performed at the Royal Society in 650 1728 in response to Rizzetti’s De Luminis Affectionibus. In his article published in 651 Philosophical Transactions, Desaguliers noted that ‘we hear indeed in a letter from Sir 652 – 653 67 Journal Book Original 14 (1726 1731), JBO/14, 21 March 1727, 10 April 1728, 27 June 1728, and 31 October 1728, pp. 191, 235, 249–250, Royal Society Library, London. 654 68 Sir Isaac Newton, The Correspondence of Isaac Newton, 7 vols., (ed. H.W. Turnbull, J.F. Scott, A.R. 655 Hall and L. Tilling), Cambridge: Cambridge Unviersity Press, 1959–1977, vol. 1, p. 96. 656 69 Aberration occurs because lenses have a different refractive index for each different wavelength of light. ’ 657 70 A. Rupert Hall, All Was Light: An Introduction to Newton s Opticks, Oxford: Clarendon Press, 1993, p. 96. 658 71 Hall, op. cit. (70), pp. 96–97. See also Kirsten Walsh, ‘Newton’s epistemic triad’, PhD dissertation, 659 University of Otago, 2014, p. 104. 660 72 Sir Isaac Newton, Opticks, New York: Dover, 1952, p. 26; Hall, op. cit. (70), p. 97. 16 Anna Marie Roos

661 Thomas Dereham to Sir Hans Sloane, President of the Royal Society, that now Signior 662 Rizzetti alledges, that he was deceived in his experiments by reason of the badness of his 663 prisms which he had from Venice’.73 In other words, Rizzetti claimed he did not have 664 ideal experimental conditions due to the quality of his prisms. 665 As Simon Schaffer has shown in his essay ‘Glass works’, the quality of the prisms was 666 important; Francesco Algarotti’s attempts in Bologna in 1726 to replicate the experimen- 667 tum crucis were described by Rizzetti as failures since he could not isolate a single red ray 668 of light; Algarotti eventually realized that his prisms were defective, and he had success at 669 replicating the experimentum crucis when he tried again with some top-quality English 670 prisms.74 Schaffer shows us how and why acceptance or denial of the specific experimen- 671 tal apparatus became a flashpoint in disputes over knowledge and method; we see the 672 beginnings of the establishment of standards for professional instrumentation, or what 673 has been termed the sociology of calibration. 674 Schaffer did not analyse as much the debate over Newton’s Opticks in Italy, which 675 continued long after Desaguliers’s 1728 demonstrations in the Royal Society.75 Long 676 after Isaac Newton’s fame was recognized, Venetian natural philosophers had an atti- 677 tude of ‘critical acceptance, if not open aversion’, towards Newtonianism.76 Part of 678 the reason for Folkes’s travels in Venice was so that he could serve in Desaguliers’s 679 stead as a Newtonian demonstrator, and the quality of Folkes’s prisms was still the 680 focus of inquiry for Venetian intellectuals. It seemed particularly important that 681 Folkes prove the truth of Newtonian optics in the city whose glass had been the ‘standard 682 against which other glass was to be compared’.77 Folkes’s status as a protégé of Newton 683 and a vice president of the Royal Society (his office conferred by Sloane six weeks before 684 his travels), and his fluency in Italian and French, were also helpful assets. 685 On 9 July 1733, Folkes received a letter from Abbé Conti, who began, ‘I beg you to 686 bring these Italian manners to an end and to treat me as a friend, that is the first 687 favour I am asking you’.78 Conti related that his colleague, Giovan Bernardo Pisenti 688 (d. 1742), having heard of the success of past demonstrations of Newtonian optics, 689 requested ‘to see demonstrated geometrically the order of the colours of the image’.79 690 Pisenti was a Somasco cleric educated by the Jesuits who also studied with Eustachio 691 692 73 J.T. Desaguliers, ‘Optical Experiments made in the beginning of August 1728, before the President and 693 Several Members of the Royal Society, and Other Gentlemen of Several Nations, upon Occasion of Signior Rizzetti’s Opticks …’, Philosophical Transactions (1727–1728) 35, pp. 596–629, 598–599. 694 74 Simon Schaffer, ‘Glass works: Newton’s prisms and the uses of experiment’, in David Gooding, Trevor 695 Pinch and Simon Schaffer (eds.), The Uses of Experiment: Studies in the Natural Sciences, Cambridge: 696 Cambridge University Press, 1989, pp. 67–104, passim; Casini, op. cit. (63), p. 222. ’ 697 75 To be fair, Schaffer does acknowledge the controversy over the nature of Newton s genius and his posthumous legacy in his ‘Fontanelle’s Newton and the uses of genius’, L’Esprit Createur (Summer 2015) 698 55(2), pp. 48–61. 699 76 Vincenzo Ferrone, Intellectual Roots of the Italian Enlightenment, Atlantic Highlands, NJ: Humanities 700 Press, 1995, p. 95. 701 77 Schaffer, op. cit. (75), pp. 72, 99. 78 Letter from Antonio Conti to Martin Folkes, 9 July 1733, MS 790/28, correspondence of Martin Folkes, 702 Royal Society Library, London. 703 79 T.E. Jessop, A Bibliography of George Berkeley, 2nd edn, New York, Springer, 1973, p. 9. Pisenti’s was 704 the first translation of Berkeley’s work on vision into any language: George Berkeley, Saggio d’una nuova teoria Taking Newton on tour 17

705 Manfredi in Bologna, and he himself served as a personal tutor to Girolamo Ascanio 706 Giustiniani; Folkes’s diary shows that he spent much of his time in Venice at the 707 Guistiniani Palace with Girolamo’s family, so it is likely that he met Pisenti there.80 708 Pisenti was also the translator of George Berkeley’s An Essay towards a New Theory 709 of Vision (1709) into Italian, and dedicated his translation to Berkeley’s friend Sir 710 John Percival, with whom he was also acquainted.81 In scholar Antonella Barzazi’s 711 opinion, the initiative to publish Berkeley’s work was probably born in the wake of 712 the Newtonian optics controversy aroused in the Venetian world by the attacks of 713 Rizzetti; Berkeley refuted an account of distance vision of Malebranche and Descartes 714 which required tacit geometrical calculations, that we perceive space by lines and angles. 715 Malebranche and Descartes argued that distance was judged by the geometry of angles 716 between the eyes and the perceived object, or via the angles of light rays that fall upon the 717 eye.82 One thus judges distances by the optic axes of the eyes which form an angle at the 718 object; whether than angle is great or small, we judge if the object is far or near. Berkeley 719 rejected those accounts and was quite negative about using Euclidean geometry of the 720 visual world as the sole basis for visual perception. Berkeley argued against the classical 721 scholars of optics by claiming that space is perceived by experience. As Berkeley later 722 stated in his Philosophical Commentaries, ‘The common Errour of the Opticians, that 723 we judge of Distance by Angles strengthens men in their prejudice that they see things 724 Q12 without and distant from their mind’.83 In Berkeley’s view, the visual perception of dis- 725 tance was explained by the association of ideas of both sight and touch, and this asso- 726 ciative approach challenged appeals to geometric calculation that profess to explain 727 completely monocular vision and the moon illusion, ‘anomalies that had plagued the 728 geometric account’.84 729 Visual perception of distance was also of great interest to Folkes. We recall his conver- 730 sations with Algarotti about the friezes on Trajan’s Column. Folkes also gave advice to 731 Robert Smith FRS, Plumian Professor of Astronomy at Cambridge University, in his A 732 Compleat System of Opticks in Four Books (1738). Cantor has judged that the work 733 was the most ‘famous book dealing with the subject’ after Newton’sownOpticks 734 735 sopra la visione … ed un discorso preliminare al Trattato della cognizione (tr. Giovanni Pisenti), Venice: 736 Francesco Storti, 1732. Pisenti also translated Berkeley’s work on cognition. 737 80 Don Gasparo Leonarducci, La Provvidenza, cantica seconda, Venice: dalla tipograia di alvisopoli, 1828, p. 5. This is a history of the Somasco congregation. 738 81 Giovanni Antonio Moschini, Della letteratura veneziana del secolo XVIII fino a’ nostri giorni, vol. 1, 739 Venice: Dalla Stamperia Palese, 1806, p. 169. 740 82 Daniel E. Flage, ‘George Berkeley (1685–1753)’, Internet Encyclopedia of Philosophy,atwww.iep.utm. 741 edu/berkeley, accessed 3 December 2016. This is a peer-reviewed and scholarly encyclopedia. 83 Casini, op. cit. (63), p. 217; Antonella Barzazi, Gli Affanni dell’erudizione: studi e organizzazione 742 culturale degli ordini religiosi a Venezia tra Sei e Settecento, Venice: Istituto Veneto di scienze, lettere ed 743 arti, 2004, p. 181. Margaret Atherton, Berkeley’s Revolution in Vision, Ithaca, NY, Cornell University 744 Press, 1990, p. 3, and Chapters 2 and 2 passim. Atherton argues that Berkeley primarily had in mind the 745 work of Descartes and Malebranche in his refutation of the geometric theory of vision; George Berkeley, ‘Philosophical commentaries’,inThe Works of George Berkeley, Bishop of Cloyne (ed. T.E. Jessop and A. 746 A. Luce), London, Nelson, 1948–1964, vol. 1, p. 603. 747 84 Flage, op. cit. (82). The moon illusion is that the moon when just above the horizon appears much larger 748 than when it is overhead. 18 Anna Marie Roos

749 (1704).85 Smith acknowledged Folkes for his ‘curious remarks’ on fallacies in vision, 750 applying optics to explain phenomena such as ‘the sun’s apparent distance, on the appar- 751 ent figure of the sky, on the apparent curvity of the sides of long walks and ploughed 752 lands, and the changes of curvity by the observer’s motion’.86 753 Folkes had also spoken to Algarotti about Molyneux’s problem in some depth.87 The 754 Irish natural philosopher William Molyneux (1656–1698) had asked John Locke 755 whether, if a blind person could suddenly see, he or she would be able to recognize by 756 sight an object’s shape they previously only knew by touch. Presented with a globe 757 and a cube, could such a person determine which was which just by looking? An affirma- 758 tive answer meant that one believed in a rationalist and innate conception of space 759 common to touch and sight. A negative answer indicated an empiricist view, that this 760 was a relationship that we learn only through experience. Locke responded in his 761 Essay Concerning Human Understanding that the formerly blind person would not be 762 able to say with certainty ‘which was the globe, which the cube … though he could 763 unerringly name them by his touch’; the connection between the senses was learned.88 764 Berkeley also offered a negative response, that a perception of distance was an ‘act of 765 Q13 judgment grounded on experience’.89 766 However, well before Diderot’s famous essay Letter on the Blind (1749), Folkes spoke 767 to Algarotti about Molyneux’s problem in reference to the case of Nicholas Saunderson 768 (1682–1739), the blind Lucasian Professor at Cambridge and fervent Newtonian who 769 lost his sight at twelve months from smallpox and who could purportedly judge the 770 size of a room and his distance from the wall by sound. Saunderson made Newton’s 771 Opticks the basis of several lectures that he made at Cambridge, including some on 772 the theory of vision.90 Folkes was a close colleague of Saunderson and commissioned 773 a painting of him. Saunderson affirmed he could have distinguished the objects with 774 his sight restored, namely because he innately understood the mathematical definition 775 of a sphere and cube and could identify them from the number of vertices they would 776 present to him, as well as the shape of their cast shadows. This was an argument 777 drawn out of Saunderson’s Treatise of Algebra, in which he proved that the cube 778 could be divided into six equal pyramids having their vertices at the centre of the cube 779 and the six faces as their bases; ‘this is used for an elegant proof that a pyramid is 780 781 782 783 85 Geoffrey Cantor, Optics after Newton: Theories of Light in Britain and Ireland, 1704–1840, 784 Manchester: Manchester University Press, 1983, p. 19. 785 86 John Nichols, Literary Anecdotes of the Eighteenth Century, London: Nichols, Son and Bentley, 1812, p. 538. 786 87 Mazzotti, op. cit. (55), p. 143. 787 88 Dialoghi Sopra l’Ottica Neutoniana in Opere Varie Del Conte Francesco Algarotti, Venice: Giambiatista 788 Pasquali, 1757, vol. 1, p. 317. 789 89 George Berkeley, Essay towards a New Theory of Vision, in the Works of George Berkeley, op. cit. (83), p. 186; John W. Davis, ‘The Molyneux Problem’, Journal of the History of Ideas 21, 3 (July-September 1960), 790 pp. 392–408, on p. 396. 791 90 Nicholas Saunderson, The Elements of Algebra, in Ten Books, vol. 1, Cambridge: Cambridge University 792 Press, 1741, p. vi. Taking Newton on tour 19

793 one-third of a prism having the same base and height’.91 Folkes, as a Newtonian math- 794 ematician, believed there was an innate geometrical quality to vision and was a very sup- 795 portive subscriber to Saunderson’s Treatise of Algebra, putting money in for eight books, 796 Q14 ‘4 Royal and 4 common paper’.92 797 In order to create a demonstration to counter directly Rizzetti’s disavowal of 798 Newtonian optics and tacitly Berkeley’s caution about using optics as the sole means 799 of explaining vision, Conti wrote to Folkes for advice. Conti indicated to Folkes that 800 he made a figure ‘to show visibly the different relative refrangibility’, showing ‘the differ- 801 ent perpendiculars with which are made the angles of the refraction of the exiting rays; 802 these angles are as small as the others that are made with the internal perpendicular are 803 large’.93 He then indicated to Folkes, 804 You would do me a favour if you told me whether you imagine that [refrangibility] in the same 805 way. The obscurity of Mr Newton’s book consists in failing to give the Theory of the refractions 806 of the rays exiting a prism, that is what he had to start with in order to remove any doubt.94 807 808 Conti was right. Newton had only conjectured in the Opticks about these issues rather 809 sparsely; for instance, although Newton analogized about the behaviour of light and 810 matter, he really did not even assert the materiality of light. As Geoffrey Cantor has 811 shown, later popularizers of Newton, such as Desaguliers, Smith and later Willem ’ – ’ ’ 812 Jacob s Gravesande (1688 1742) interpreted Newton s Opticks as, if in Cantor s ‘ ’ ‘ 813 Q15 phrase, it were an appendix to the Principia , in which forces were employed to 814 explain all those phenomena in which light deviated from its natural rectilinear ’ 95 815 path . In this form of projectile optics, light was postulated to travel in a straight fi fl 816 line with nite velocity, and refraction was explained by the in uence of attractive 817 forces. One could say, for instance, that refractive dispersion was due to a particulate 818 model of light, the rays or bodies being of different sizes, the violet-making rays the smal- 96 819 lest and the red-making ones the largest and heaviest. 820 Conti then went on to mention the work of Paris lawyer and Anglophile Nicolas 821 Gauger, who in 1727 produced a long account defending Newtonian optics. In July 822 1727, Gauger had written Conti a twenty-page letter which was publicly printed, addres- ’ 823 sing the danger of Rizzetti s attacks on the Newtonian system, with particular mention of 97 fi 824 the two-colour-card experiment. But ve years later, Conti lamented to Folkes that ‘ … ’ 825 although Mr Gauger has given it quite amply I don t know if his book is still ’ ‘ 826 being printed . He went on, It is certain that if the ray was not divided into several 827 threads, so they made different angles, you would see the image differently from how 828 829 91 Denis Diderot, ‘Letter on the blind’, in M.J. Morgan, Molyneux’s Question, Cambridge: Cambridge 830 University Press, 1977, p. 33. 831 92 Saunderson, ‘Index of subscribers’, op. cit. (86). 832 93 Conti, op. cit. (78), MS 790/28. 833 94 Conti, op. cit. (78), MS 790/28. 95 Cantor, op. cit. (85), p. 26. 834 96 Cantor, op. cit. (85), p. 31. 835 97 Nicolas Gauger, ‘Lettre à M. l’abbé Conti, juillet 1727’, Continuation des Mémoires de Littérature et 836 d’Histoire (March 1728) 5(1), pp. 10–51. 20 Anna Marie Roos

837 we see it … I am waiting for your decisions on this’.98 But such pedagogically clear, if 838 sometimes superficial, explanations by Newtonian pedagogues had not reached or con- 839 vinced all Venetian ears; hence Conti’s plea to Folkes for a proper diagram and clarifi- 840 cation of refrangibility. 841 Shortly after this exchange, on 5 August 1733, Folkes met Rizzetti himself, recording 842 that Father Giovanni Crivelli ‘calld on me with Sigr. Rizzetti author of a book which he 843 gave me of the nature of light and colours against Sir Isaac Newton’.99 Crivelli had 844 written Elementi de fisica in 1731, a textbook which was a reinterpretation of recent dis- 845 coveries in natural philosophy within an Aristotelian framework. Historian Vincenzo 846 Ferrone considered Crivelli’s work as reflecting the attitude of a large segment of 847 Venetian society towards Newton’s works.100 While the first volume offered the most 848 complete, if dispassionate, explanation of Newtonian gravity that has appeared in 849 Italy (for example, he rejects Newton’s concept of a vacuum in space), the explanation 850 of the Opticks is equally neutral. Crivelli presented both Newtonian optics and the 851 objections of Rizzetti in a manner that subtlely neutralized them, doing the same thing 852 in his coverage of astronomy, noncommittally describing Copernican, Tychonic and 853 Ptolemaic hypotheses with little comment.101 Although one receives the impression 854 from reading his manual that there was wide-ranging knowledge of Newtonian theory 855 in the Veneto, one also receives the impression that there was a rejection of any sort 856 of Newtonian orthodoxy.102 In this light, Crivelli’s visit with the antagonistic Rizzetti 857 in tow may be interpreted as a challenge to the Newtonian Folkes. 858 After Rizzetti’s visit and a short period of illness (Folkes and his wife contracted a kind 859 of heat rash termed scotture), Folkes met Conti on 23 July. The latter had just come to 860 town and upon hearing about Rizzetti’s visit to Folkes proposed that he and Folkes act 861 and publicly ‘make some of Sir I[saac] Newton’s experiments on fryday next’. 862 Folkes subsequently indicated in his travel diary on Friday 27 August 1733: ‘I was of the Palace 863 Justinian in the morning, to have made some of Sir Isaac Newtons optical experiments but the 864 Sun not stirring I could no more than get things in order for another day. The apparatus 865 belonged to Abbe Conti who was home and he had brought some very good prisms from 103 866 England. 867 Clearly on the hunt for apparatus, Folkes had three days earlier indicated, ‘I was also at 868 another person who is a practical Mathematician to see some instruments but nothing 869 was particular what he had best were some English things’.104 870 Q16 On 28 August 1733, Folkes recorded triumphantly, ‘I was again at the Guistiniani 871 Palace and made most of the experiments of the first book of opticks with very good 872 success and to the satisfaction of all that were here which were … men of the first 873 874 875 98 Conti, op. cit. (78), MS 790/28. 876 99 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 30r. – 877 100 Ferrone, op. cit. (76), pp. 98 99. 101 Ferrone, op. cit. (76), p. 99. 878 102 Ferrone, op. cit. (76), p. 99. 879 103 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 39r. 880 104 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 39r. Taking Newton on tour 21

881 people of Venice’.105 Folkes was rewarded by Guistiniani with a present of ‘spanish 882 Chocolate’.106 On 2 and 7 September, Folkes then indicated, 883 I was again to prepare some of the Experiments of the Opticks at Sr. Guistinianis, our 884 Experiments there have made a good deal of noise and many of the chief Nobility are very desir- 885 ous to see some of them which I have promised to repeat on Saturd tuesday next though it is but 886 in a gross manner I can make them want of a convenient apparatus. They are very satisfactory … 887 and carry demonstration to all that are capable of comprehending them I made the Experiment I had intended at the Justinian Palace. I have now shewn all that are considerable 888 in the Book of Opticks in the first book, and though my apparatus was none of the best I was 889 sufficiently satisfyd with them and am told it is what was never done with any success here 890 before, there were several of the Chief nobility and some others here present. and every one 891 that has any sense seems thoroughly satisfyd as far as he understands. tho I was a little surprised at some mistakes Crivelli fell into and [he] was pretty obstinate … a great while which showed 892 me he is not so perfect master of the philosophy as I thought before.107 893 894 Considering Crivelli’s neutral stance in presenting Newton’s optics in his Elementi, his 895 obstinate behaviour during the demonstration was not surprising. Rizzetti also contin- 896 ued his anti-Newtonian campaign until the 1740s, with diminishing success. 897 Nonetheless, Folkes’s performance had the required effect. When he left Venice, 898 Folkes noted that his experimental success showed that he had ‘conversd with many 899 of them [the Venetians] in a manner no English man almost has done before me’.108 900 In a letter from the physician Pietro Michelotti to John Machin, secretary of the Royal 901 Society, Michelotti indeed indicated that Folkes had spent several days staying with 902 him in Venice, indicating close familiarity.109 Several of the Newtonian adherents in 903 Venice that Folkes indicated in his diary that he met in Venice, including Ludovico 904 Riva (1698–1746), professor of astronomy at Padua, were subsequently put forward 905 Q17 for election in the Royal Society and became fellows.110 Although Folkes worried 906 about his apparatus, his use of Conti’s ‘very good’ English prisms and his expertise in 907 his demonstrations vindicated, or so he was told, Newtonian optics in the Veneto. 908 909 105 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 39r. 910 106 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 39r. 911 107 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), ff. 39r–40r, italics added. 912 108 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 44r. 913 109 Pietro Antonio Michelotti to John Machin, 6 October 1733, EL/M3/32, Royal Society Library. Michelotti noted, ‘I have often understood from that most noble and intelligent gentleman Mr. Martin 914 Folkes, a man furnished with every kind of virtue, who is still staying with me, that you have the most 915 clear-sighted opinions in respect of the disciplines of mathematics and physics (in which I too take 916 enormous delight)’. Folkes appended a letter of introduction for Michelotti to Machin to this piece of 917 correspondence. 110 Folkes nominated Riva by letter on 1 October 1733 as a Fellow of the Royal Society, as a ‘Person of 918 great Modesty and knowledge in his way and Author of Several Works, which he hath given me to be 919 presented to the Society, one of which is a dissertation on certain fiery Meteors, that have lately appeared 920 and done a pretty deal of Mischief. He is likewise strongly recommended by the Marquis Poleni and Dr ’ 921 Michaelotty . Riva was elected on 24 January 1733/4. See EC/1733/07, the Royal Society, London. The dissertation that was mentioned was ‘an account of some surprizing Meteors appearing from time to time in 922 the Province or Trevegiana (in the dominions of Venice) described and explained by Signor Ludovico Riva 923 in his Miscellanies in Latin’, read to the Royal Society on 5 December 1734; see Register Book Original, 924 RBO/19/5, the Royal Society, London. 22 Anna Marie Roos

925 Folkes continued his Newtonian campaign when he travelled to Florence, but he still 926 worried about the quality of his equipment. In a letter of c.1734 to Sir Philip Stanhope 927 (who was on his own Grand Tour at the time) Folkes wrote, 928 The morning promising very finely Dr Cocchi has just sent to me to desire if I could to try to 929 make some to Sr Isaacs Prismatic Experiments at his house; at which both he and my self 930 should esteem your Lordships company a great honour … I can make them but in a bungling 931 sort of a manner by reason the tackle is very indifferent …111 932 Folkes’s son, also named Martin, was sent to take Earl Stanhope to the house of Antonio 933 Cocchi, a well-known physician and defender of Newton whom Folkes met in 1723, 934 where the experiments were performed.112 It does not seem that Folkes’s comments 935 about his equipment were the result of a false modesty, as the presentation of the 936 optical experiments was important due to the importance of the participants in the audi- 937 ence. Folkes invited ‘Mr Rhodes’, secretary to Charles Fane, the British minister in 938 Tuscany, and ‘Mr Mann’ or Sir Horace Mann, 1st Baronet (1706–1786), the long-stand- 939 ing British resident in Florence. (Folkes and Mann had been at Clare College, 940 Cambridge, together, where they initially met).113 941 The presentation was much less public, probably because outside the safety of the 942 Venetian Republic, the Inquisition was active and dangerous; it placed Locke’s Essay 943 on Human Understanding on the Index in 1734. Algarotti’s Il Newtonianismo per le 944 dame had also been condemned as Masonic, and the Inquisition denounced 945 Newtonian Antonio Conti, whom Folkes had met in Venice. Open acceptance of 946 Newtonian gravitation was impeded because the Catholic Church still banned belief 947 in the Earth’s motion, and the refutation of Newtonian colour theory in itself was an 948 implicit opposition to a moving Earth.114 Although we do not know the specific 949 outcome, we do know that upon Folkes’s return, when he informed Cocchi of his 950 intention to visit Italy again, Cocchi replied that he was ‘overjoy’d’ at Folkes’s decisions. 951 Conti offered to make domestic arrangements for Folkes during his planned visit, 952 and reminded him to bring a telescope and microscope from England. Conti added, 953 Q18 ‘I should very proud if you would habilitate my Terrace with Some of your 954 Astronomical Observations … and other physical experiments which would be very 955 much admired here’.115 Folkes in his correspondence in subsequent years also success- 956 fully cultivated Stanhope as a fellow mathematician working on problems of series 957 958 111 U1590_C21_6a, Stanhope Papers, Kent County Archives. 959 112 For a comprehensive biography of Cocchi see Luigi Guerrini, Antonio Cocchi naturalista e filosofo, 960 Florence: Polistampa, 2002; Cocchi and Folkes also were both Freemasons, and Cocchi later became master ‘ ’ 961 of the Florentine Lodge. See Nicholas Hans, The masonic lodge in Florence in the eighteenth century , Ars Quatuor Coronatorum (1958) 61, pp. 109–112. Folkes’s son also would attend several meetings at the 962 Royal Society when he returned from England, as a means of furthering his education. 963 113 In a letter to Walpole, Mann recalled speaking with Folkes, and the editor speculated that Mann and 964 Folkes may have met in Italy. Indeed they did. Horace Mann to Horace Walpole, Horace Walpole’s – 965 Correspondence, New Haven, CT: Yale University Press, online edn, 19 April 1777, vol. 24, pp. 289 290 n. 3, http://images.library.yale.edu/hwcorrespondence/default.asp, accessed 2 November 2016. 966 114 Casini, op. cit. (63), p. 220. See also Paolo Cassini, Hypotheses Non Fingo: Tra Newton E Kant, Rome: 967 Edizioni di storia e letteratura, 2006, p. 108. 968 115 Cocchi to Folkes, 3 March 1736, MS/790/26, Royal Society Library. Taking Newton on tour 23

969 and probability, so his demonstration was probably convincing.116 When Folkes was in 970 Venice, he was questioned by several virtuosi, such as Cristino Martinelli, about the 971 probability problems and the odds of winning the Pope’s Lottery, so he was known 972 Q19 for his expertise in this area.117 In Venice and Florence, Folkes thus successfully demon- 973 strated Newtonian optics, cultivated fellow natural philosophers, and fashioned himself 974 as a ambassador of Newtonianism. 975 976 Folkes, Venice and Celsius 977 978 Not only did Folkes demonstrate the primacy of Newtonian optics as well as awareness 979 of standards of professional equipment during his journey, but he also had another 980 encounter that would contribute to the primacy of Newtonianism and English instru- 981 ments. On 18 September 1734, while he was in Venice, Folkes recorded in his diary a 982 meeting with 983 2 Swedish Gentlemen. Mr Schelsius Prof. of Astronomy at Upsal, and a young Gentleman who 984 travels at the Kings expense to study Architecture. they [Celsius and his companion] are very 985 well bred understanding men and make a handsome figure. Mr Schelsius presented me with 986 a book he has published on the Aurora borealis.118 987 ‘Schelsius’ was, of course, Anders Celsius, his work on the aurora borealis the Nova 988 Methodus distantiam solis a terra determinandi (New Method for Determining the 989 Distance from the Earth to the Sun), which was first read to the Royal Society on 8 990 April 1736, and printed in Philosophical Transactions. Celsius was also one of the 991 first to suggest a connection between aurorae and changes in the Earth’s magnetic 992 fields, and he would also make observations of sightings in England.119 Folkes would 993 have been very interested to talk to Celsius as Folkes himself made some of the earliest 994 sightings of aurorae from King’s Lynn, Norfolk, not too far from his country seat, 995 Hillington Hall. The early part of the century saw the end of the Maunder minimum, 996 and London, Plymouth and King’s Lynn were ideally situated to observe aurorae 997 (Figure 3).120 998 Folkes then noted the next day, 999 1000 1001 116 Folkes had a pervasive interest in games of chance and was presented with a probability calculations about the game of whist from George Lewis Scott, 25 April 1744, MS 250/26, Royal Society Library. 1002 117 Folkes, ‘Journey from Venice to Rome’, op. cit. (1), f. 39r. Martinelli owned a Hauksbee-type air pump 1003 which was bought by the Republic of Venice in 1738–1739 for the new chair of experimental philosophy at the 1004 university; the pump was used by Giovanni Poleni for his lectures on experimental philosophy. See Terje ‘ ’ 1005 Brundtland, Francis Hauksbee and his air pump , Notes and Records of the Royal Society (2012), pp. 1–20, 15. The pump is still extant at the Museo di Storia della Fisica in Padua. For Stanhope and Folkes 1006 see David Bellhouse, ‘Lord Stanhope’s papers on the doctrine of chances’, History of Mathematics (2007) 1007 34, pp. 173–186. 1008 118 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 42r. ’ 1009 119 Record of the reading of Celsius s book is in the Register Book Original, RBO/16/57, Royal Society Library; see also Anders Celsius, ‘Observations of the Aurora Borealis Made in England by Andr. Celsius, 1010 F. R. S. and Secr. R. S. of Upsal in Sweden’, Philosophical Transactions (1735) 39(441), pp. 241–244. 1011 120 Mike Lockwood and Luke Barnard, ‘An arch in the UK: aurora catalogue’, A & G: News and Reviews 1012 in Astronomy and Geophysics (August 2015) 56, pp. 4.25–4.30, 4.26. 1056 1055 1054 1053 1052 1051 1050 1049 1048 1047 1046 1045 1044 1043 1042 1041 1040 1039 1038 1037 1036 1035 1034 1033 1032 1031 1030 1029 1028 1027 1026 1025 1024 1023 1022 1021 1020 1019 1018 1017 1016 1015 1014 1013

Fig. 3 - Colour online, B/W in print etrfo atikt oks 0Mrh12/,EL/R1/61, 1726/7, March 20 Folkes, to Rastrick from Letter 3. Figure 24 naMreRoos Marie Anna uoabrai bevdb ila atik n fFolkes of one Rastrick, William by observed borealis Aurora © h oa Society. Royal the ’ egbusi Norfolk. in neighbours s Taking Newton on tour 25

1057 I had invited the 2 Swedish Gentlemen, and I passd the day with them, they gave me several 1058 curious accounts both of their own country and their observations in Germany, they also gave me the measure and weights of their own country in which they have been both been 1059 very curious, and I am so well satisfied of their acquaintance that tis a satisfaction they are 1060 going the same way and will be of service to me observing the same things as my self. 1061 fi 1062 More importantly, Folkes indeed would be involved with the scienti c work of Celsius, 1063 assisting him with his geodesic expedition with Maupertuis to measure the shape of the ’ 1064 Earth. The argument over the Earth s shape involved predictive calculations by Newton, 1065 and thus its outcome was crucial to the primacy of Newtonianism. When Celsius came to fi 1066 London to procure scienti c instrumention for the expedition, was he introduced by 1067 Folkes not only to key members of the Royal Society, but also to fellows of the 1068 Society of Antiquaries, as Folkes promoted close ties between the two organizations, 1069 which had common interests in metrology. 1070 When he met Folkes, Celsius had just been to Paris on a grand tour of European obser- 121 1071 vatories and had met Algarotti in Italy. And when they arrived in Paris together at the 1072 end of the summer of 1734, Algarotti introduced Celsius to Maupertuis and his collea- 1073 gues. Here the idea for the Lapland expedition to measure the true shape of the Earth was fi fi 1074 born and given a royal warrant ve months later to nd and provision a ship to take the 122 1075 travellers to Stockholm. The expedition would help settle a dispute that Maupertuis 1076 had with French cartographer Jacques Cassini over whether the Earth was prolate 1077 (longer along its axis from north to south), or oblate (broader along its diameter at 1078 the equator). Cassini believed that the Earth was prolate. Maupertuis in his expedition, 1079 and Newton with predictive calculation, proved it was oblate. The expedition to 1080 Lapland, lasting from July 1736 to March 1737, measured an arc of the meridian fi 1081 from Tornea to Kittis. The scienti c party consisted of Maupertuis, Clairaut, Camus, 1082 Le Monnier, the Abbé Outhier and of course Celsius, who would measure the meridian 1083 arc near the North Pole. Another expedition organized by the French to South America – 1084 (1735 43) near the equator to measure the meridian arc would eventually demonstrate ’ 1085 that Newton was correct about the Earth s shape. fi 1086 The travellers would use a xed-length pendulum clock, a theodolite and a zenith 1087 sector that could the measure the shape of the Earth in tropical, temperate and Arctic fi 1088 latitudes. The rst method depended on the comparison of the periods of pendulum 1089 clocks at different latitudes, eliminating the temperature-dependent variable (clocks 1090 went a second a day slower for every two divisions of temperature rise on the thermom- 123 1091 eter). Newton in his Principia noted that astronomers found that pendulum clocks 1092 moved slower near the equator, thus supporting his prediction that their increase in 1093 1094 121 See also N.V.E. Nordenmark, Anders Celsius: Professor I Uppsala 1701–44, Uppsala: Almqvist och 1095 Wiksells boytryck, 1926. 1096 122 Mary Terrall, The Man Who Flattened the Earth: Maupertuis and the Sciences in the Enlightenment, ‘ 1097 Chicago: The University of Chicago Press, 2002, p. 102. See also Rob Iliffe, Aplatisseur du monde et de Cassini: Maupertuis, precision measurement, and the shape of the Earth in the 1730s’, History of Science 1098 (1993) 31, pp. 335–375. 1099 123 This explanation is adapted from Richard Sorrenson, ‘George Graham, visible technician’, BJHS (1999) 1100 32, pp. 203–221, 210–211. 26 Anna Marie Roos

1101 weight from the equator to the poles was as the square of the sine of the latitude.124 1102 Other than comparing the period of pendulum clocks, one could use a theodolite and 1103 surveyors’ rods to measure out a large distance (sixty to seventy miles) and, using a 1104 zenith sector, measure the degree of arc that distance covered, a more direct means of 1105 measuring the Earth’s surface. 1106 As Celsius was on his way to London, Maupertuis asked him to obtain several instru- 1107 ments made by George Graham.125 Maupertuis desired a model of Graham’s portable 1108 zenith sector, for observing the transits of fixed stars that allowed for the calculations 1109 of latitude; it was this sector with which in 1728 James Bradley had also discovered 1110 the aberration of starlight measuring Gamma Draconis. Gamma Draconis has a high 1111 northerly position of 51.5 degrees north of the celestial equator, which takes it 1112 through the zenith, as seen from London. The atmosphere of the Earth causes refraction 1113 of light, which makes stars appear higher than they really are, but using a star that passes 1114 directly overhead like Draconis solves such problems. Draconis was thus used to 1115 measure stellar parallax. However, in his work with Samuel Molyneux, Bradley detected 1116 a small apparent motion of Draconis not due to parallax (the annual timetable for 1117 Draco’s parallax was different), but instead due to what is termed stellar aberration 1118 resulting from the finite speed of light and the orbital motion of the Earth.126 1119 Maupertuis and Folkes had become friends in 1728 during the Frenchman’sown 1120 Grand Tour. Folkes was a chief patron of Graham, having nominated him to the fellow- 1121 ship of the Royal Society, on 8 December 1720.127 Folkes also appended to his ‘memo- 1122 randa’ a list of prices for Graham’s watches, often securing them as gifts for his scientific 1123 correspondents. Folkes and Graham were close friends, recorded in John Byrom’s diary 1124 as often socializing in various coffeehouses or taverns such as the Sun after Royal Society 1125 meetings (Figure 4).128 When Celsius was in London in 1735, he observed a lunar eclipse 1126 from Graham’s house using some of Bradley’s new telescopes. 1127 Celsius was also invited to attend meetings at both the Royal Society (where he dis- 1128 cussed aurora borealis he had seen in Sweden), and to meetings of the Society of 1129 Antiquaries, showing his deep connections between the two organizations. For instance, 1130 on 13 November 1735 Celsius presented at Antiquaries ‘a draught of two kinds of Runic 1131 Characters, namely the Vulgar and Helsingic together with some remarks on them’, 1132 1133 1134 1135 124 Sorrenson, op. cit. (123), p. 211. 1136 125 Terrall, op. cit. (122), p. 137. In his letter to Celsius, Maupertuis indicated that he wished for a model of ’ fi ’ 1137 James Bradley s instrument for observing the transits of xed stars as well as Graham s astronomical pendulum clock. See extract of a letter from Pierre Maupertuis, dated Paris, 22 November 1735, to Andreas Celsius, EL/ 1138 M3/24, Royal Society Library, London. 1139 126 James Bradley, ‘A Letter from the Reverent Mr. James Bradley Savilian Professor of Astronomy at 1140 Oxford, and F.R.S. to Dr Edmond Halley Astonom. Reg. &c. giving an Account of a new discovered ’ ’ – – 1141 Motion of the Fix d Stars , Philosophical Transactions (1727 1728) 35, pp. 637 661. 127 Journal Book Original 13 (1720-26), 8 December 1720, JB0/13/18, Royal Society Library, London. 1142 128 Byrom, op. cit. (8), vol. 1, p. 109: 1725. ‘Tuesday, 6th April … to Paul’s Church Yard, where Mr. 1143 Leycester and I went, Mr. Graham, Foulkes, Sloan, Glover, Montagu … There was a Lodge of Freemasons 1144 in the room over us, where Mr. Foulkes, who is Deputy Grand Master, was till he came to us’. Taking Newton on tour 27

1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 Fig. 4 - Colour online, B/W in print 1162 1163 Figure 4. William Hogarth’s sketch of Folkes examining a watch, c.1720s, Button’s Coffeehouse, 1164 British Museum, image 1861.0413.508, Creative Commons BY-NC-SA 4.0 license. 1165 129 1166 found on the Malsta stone in Rogsta, Hälsingland, Sweden (Figure 5). This paper on 1167 runes was published by the Philosophical Transactions of the Royal Society in 1737 with 1168 an attempt to date the stone by examining the genealogy of the family it described and 1169 applying the rationale used to date events in Newton’s biblical Chronology of Ancient 130 1170 Kingdoms. In Folkes’s presence, Celsius attended the Society of Antiquaries again 1171 on 9 March 1735/6 and on 18 March 1735/6, where Celsius ‘delivered an account of 1172 an ancient Alabaster vase found in Sweden … at the Antiquarian College of 1173 Stockholm … which was read’; Celsius also presented the Society of Antiquaries ‘with 131 1174 a wooden print of the said vase’. As Celsius received his instruments, Folkes’s 1175 friends received an antiquarian gift, part of a time-honoured exchange characteristic 1176 of the Republic of Letters. The ties between the Royal Society, the Antiquaries and 1177 Newtonianism were strengthened. 1178 Folkes also gave advice to Celsius while he was on expedition. In December 1736, 1179 Celsius wrote to Folkes stating that he was ‘one thousand times grateful for the 1180 ‘“ ” 1181 129 Anders Celsius, Lapis Maltadensis : transcription and translation of a runic inscription on the Malsta stone in Rogsta, Hälsingland, Sweden by Prof. Anders Celsius, Hon. FSA’, Society of Antiquaries of London 1182 Minute Book (SAL), SAL/MS/264 B, vol. 2, p. 309, Society of Antiquaries Library, London. See also 1183 S. Jansson, The Runes of Sweden, London: Phoneix House, 1962, pp. 79–80. 1184 130 Anders Celsius, ‘An Explanation of the Runic Characters of Helsingland’, Philosophical Transactions – – ‘ 1185 (1737/8) 40(7 13), pp. 7 13, 13. Celsius wrote, if we suppose Frumunt (the creator of the monument) to have been thirty years of Age when he erected this Monument for his Father, and, with Sir Isaac Newton, allow thirty 1186 Years for each Generation, we shall find three hundred and thirty Years from the Death of Fifiulsi to the Birth of 1187 Fidrasiv, who is the Stock of these Generations’. 1188 131 SAL Minute Book, SAL/MS/264 B, vol. 2, pp. 164–165, Society of Antiquaries Library, London. 28 Anna Marie Roos

1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215

1216 Fig. 5 - Colour online, B/W in print 1217 Figure 5. Sketch of Celsius’s discovery of runes on the Malsta stone in Rogsta, Hälsingland, 1218 Sweden, which was engraved and published in the Philosophical Transactions, CLP/16/51, © 1219 The Royal Society 1220 1221 courtesies you did for me during my stay in London’. He continued, ‘We have observed 1222 the difference of latitude between Torne and Pello with Mr Graham’s instrument. The 1223 observations were made in September in Pello, having not found any suitable star 1224 other than the Dragon. We then observed it in October here in Torne’.132 1225 In other words, Graham’s sector measured the angle at which a particular star, in this 1226 case Draco or the Dragon, near the zenith passed the meridian (the star’s altitude). The 1227 expedition moved then to another mountaintop at Pello and repeated the same measure- 1228 ment. The difference between the star’s altitudes was due to the party’s having travelled 1229 south. As Sorrenson stated, they then had to ‘establish the distance between the two 1230 1231 1232 132 MS 790/21, letter from Celsius to Folkes, 3 December 1736, Royal Society Library, London. Taking Newton on tour 29

1233 mountains by surveying a series of triangles and measuring several of the baselines with 1234 wooden poles’.133 Once they had the distance between the two points and the difference 1235 in angles, they ‘calculated that the length of one degree of arc near the polar circle was 1236 longer than at Paris’, and concluded that the Earth was oblate, vindicating Newton. 1237 However, there was one problem. As Celsius continued, 1238 since this star [Draco] is close to the ecliptic pole, the declination changed in the meantime.[134] 1239 That is why I beg you, Sir, to send me the rule according to which one calculates the change of 1240 declination from one month to the next. We don’t have here in memory what Mr Bradley gave 1241 about this in the Philosophical Transactions. And I would like to know as well if Mr Bradley … 1242 has established anything yet about the irregularities that he found in the stars located around the equinoxes, since our star of the Dragon is very close to that location.135 1243 1244 As mentioned, Bradley’s observations of the motion of Draco led to his discovery of 1245 stellar aberration. As Celsius was using Draco as a reference point for his triangulation 1246 measurement, he was concerned that this aberration would affect his measurements. 1247 Folkes’s reply to Celsius’s query is not extant, but we know that Bradley’s calculations 1248 regarding stellar aberration were communicated. Maupertuis, in his publications about 1249 the exhibition, incorporated Bradley’s data about declination, and used Bradley’s preci- 1250 sion in measuring stellar positions as an example of new standards of astronomical prac- 1251 tice only possible with the best instruments. Maupertuis stated, ‘Mr Bradley very kindly 1252 shared with me his latest discoveries on the motions of the stars, and communicated to 1253 me the necessary correction to the arcs we observed’. As Terrall has shown, this precision 1254 of English instruments was used as a weapon against Cassini’s claims for a prolate Earth. 1255 When Maupertuis’s book finally did appear about the shape of the Earth (Le figure de 1256 terre) in 1738, he wrote to Folkes, 1257 [136] 1258 It is my turn now to thank you after the obliging letter that you did me the honour of writing me. The most flattering reward I could get from a work[137] that has faced many diffi- 1259 culties and risks[138] is to see it has the approval of an excellent judge such as you. Such 1260 approval makes me well strong against the injustice of those who were not pleased by our mea- 1261 sures, and their conspiracy. It is true that it is something singular and that it will be difficult to [139] 1262 understand that the Astronomer [Cassini] who has the highest reputation in France was mistaken 5 different times in the measures he undertook and that he has always found that 1263 the Earth is elongated in 1701, 1713, 1714, 1733, and 1734. It seems that if there had been 1264 chance only, it should have led him better. But I am nevertheless convinced that the Earth is 1265 flattened.140 1266 1267 133 Sorrenson, op. cit. (123), p. 214. 1268 134 A star’s declination changes gradually due to precession of the equinoxes and annual parallax. Bradley’s 1269 stellar aberration was due to another phenomenon, that of nutation. 135 MS 790/21, letter from Celsius to Folkes, 3 December 1736, Royal Society Library, London. 1270 136 Obligeante lettre; that is to say, a letter that was helpful and pleasant to the reader, Maupertuis. 1271 137 The French word ouvrage is generally a ‘work’ but it could be also a book, a work of art or architecture, 1272 or any sort of work that was undertaken. ‘ ’ 1273 138 This is et de périls in the letter, where périls would rather mean risks instead of the general translation into ‘peril’ because Maupertuis in his letter is generally referring to difficulties and trouble regarding his 1274 discoveries. 1275 139 ‘Astronomer’ is written with a capital A in French in the original letter. 1276 140 Letter from Pierre Maupertuis to Martin Folkes, 26 July 1738, MS 790/42, Royal Society Library. 30 Anna Marie Roos

1277 He then continued, ‘It has been very sweet to me, Sir, to find myself still in the honour of 1278 your memory after such a long time … I [send you my book] to you as one of the first 1279 scholars in Europe’.141 1280 Folkes’s interest in stellar parallax, aberration and the modification of the constella- 1281 tions over time were demonstrated by a model he had made of the globe which he 1282 demonstrated to the Society of Antiquaries on 7 July 1736 when he returned to 1283 England. It was a plaster of Paris copy of the Farnese Globe, the oldest surviving depic- 1284 tion of this set of Western constellations; Folkes recorded in his travel diary, ‘Diam of the 1285 Farnesian Globe. 2f. 5 inch. 1/10 English Measure’, likely indicating that he saw and 1286 measured in it Rome.142 The globe puts the celestial figures against a grid of circles com- 1287 prising the celestial equator, the colures, the ecliptic, the tropics and the Arctic and 1288 Antarctic Circles. This allows for the constellations to be positioned accurately. It was 1289 noted at the Antiquaries meeting that ‘the colure of this globe passes by those parts of 1290 the asterism by which it is said to have past in the days of Hipparchus but the intersection 1291 of the Equator and Eccliptic is not at the Colure’. This was a reference to the 26,000-year 1292 precession or axial wobble on the Earth which Newton discovered shifts the positions of 1293 the celestial circles over time, so that the observed positions on the Farnese Atlas can be 1294 traced to a particular date in celestial time. ‘The declination of the Arctic and Antarctic 1295 Circles will correspond to a particular latitude for the observer whose observations were 1296 adopted by the sculptor … a detailed analysis of the globe will reveal the latitude and 1297 epoch for the observations incorporated in the globe’.143 The Society of Antiquaries’ 1298 entry in their Minute Book about Folkes’s presentation about the globe noted that its 1299 age could be determined to be during the time of the Antonine emperors. 1300 Geodesy also continued to be a preoccupation of Folkes when he eventually realized 1301 his goal of being appointed president of the Royal Society, and then the Society of 1302 Antiquaries, nearly a decade after his initial Italian visit. Folkes became one of the stron- 1303 gest supporters in the Royal Society of John Harrison and his longitude clock, convinced 1304 of Harrison’s ‘strong impulses of a natural and uncommon genius’.144 And in 1745 1305 Folkes intervened when Antonio de Ulloa, who went on the Peruvian expedition to 1306 measure the meridian arc near the equator, was captured by the English as he sailed 1307 home when the expedition was completed. Spain and Britain were at the time at war. 1308 Ulloa’s calculations were confiscated and he languished in prison in Portsmouth, until 1309 he was granted leave to travel to London at the request of the Royal Society. Folkes 1310 mediated, and on 8 May 1746 he used his knowledge of Spanish to summarize the 1311 details of Ulloa’s expedition in thirty-three pages of manuscript which he presented to 1312 1313 141 Maupertuis to Folkes, op. cit. (140). 142 Folkes, ‘Journey from Venice to Rome’ op. cit. (1), f. 98v. This was noted by Kristen Lippincott, ‘A 1314 chapter in the Nachleben of the Farnese Atlas: Martin Folkes’s globe’, Journal of the Warburg and 1315 Courtauld Institutes (2011) 74, pp. 281–299, 287; Society of Antiquaries Minute Book, vol. 2, pp. 201–202. 1316 143 B.E. Schaefer, ‘The epoch of the constellations on the Farnese atlas and their origin in Hipparchus’ lost ’ – 1317 catalogue , Journal for the History of Astronomy (2005) 36, pp. 167 196, 196. 144 Royal Society Journal Book, copy, xx, p. 184. This comment about genius was from the address Folkes 1318 gave when presenting the Copley Medal to Harrison. See Jim Bennett, ‘James Short and John Harrison: 1319 personal genius and public knowledge’, Science Museum Journal (Autumn 2014) 2, at http://dx.doi.org/10. 1320 15180/140209. 1364 1363 1362 1361 1360 1359 1358 1357 1356 1355 1354 1353 1352 1351 1350 1349 1348 1347 1346 1345 1344 1343 1342 1341 1340 1339 1338 1337 1336 1335 1334 1333 1332 1331 1330 1329 1328 1327 1326 1325 1324 1323 1322 1321

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1365 the society later that month.145 Folkes reproduced Ulloa’s triangulation and its results, 1366 which confirmed Newton’s predictions of the shape of the Earth. Folkes noted that 1367 the ‘proportion resulting of the Axis of the Earth’ from the Maupertuis expedition ‘to 1368 its Equatorial Diameter’ of Ulloa’s measurements ‘will be nearly 223 to 222 surprizingly 1369 near to that given from calculation only, by the great Sir Isaac Newton, of 229 to 230, in 1370 the last edition of his Principia’.146 Rather ironically, Folkes noted that ‘Dr Bradley’s 1371 aberration of the fixed stars from the successive propagation of light is not brought 1372 into the account’. 1373 Folkes also recorded their barometric observations made in the Andes, as well as the 1374 heights of the mountains, and included Ulloa’s ethnographic information about the 1375 Peruvians and descriptions of the flora and fauna, including the deadly coral snake. 1376 Folkes noted that he did not want the material to be made public, as Ulloa intended 1377 to publish a book about his exploits when he returned to Spain (accomplished in 1378 1748 with twelve subsequent editions in French, English, Dutch and German); Folkes 1379 noted that he was unwilling to publicize Ulloa’s findings because of the pleasure the 1380 public would ‘without doubt receive’ from Ulloa’s book.147 Apart from the evident 1381 esteem Ulloa and Folkes developed for each other, vindication of Newtonianism was 1382 all the more powerful from an outside entity. Ulloa was made an FRS, his papers 1383 were returned to him by order of the Lords Commissioners of the Admiralty, and it 1384 was arranged that he would get passage to Portugal, which was a neutral in the war, 1385 so he could get back to Spain. 1386 1387 Conclusion 1388 1389 Whether speaking in defence of Newtonian optics, or in support of Maupertuis’s flat- 1390 tened Earth, Folkes’s travel diary reveals that he made a case for the primacy and preci- 1391 sion of English instruments and measurement in natural philosophy. This precision of 1392 measurement would also extend to antiquarian questions in which conversion factors 1393 were sought between the English and Roman feet to comprehend Roman architectural 1394 engineering. The diary also represented the manifestation of Folkes as an international 1395 broker of Newtonianism, something reflected in the portraiture he commissioned of 1396 himself before and after his tour. The portrait by Jonathan Richardson painted in 1397 1718 has no indication of Folkes’s association with Newton, or even of his interests in 1398 astronomy, lacking the typical props of books or scientific instruments. Richardson 1399 instead painted this portrait to commemorate his and Folkes’s friendship, not as an 1400 – 1401 145 Martin Folkes, letters and papers, Decade 1, vol. 10A, 5 December 1745 to 1 May 1746, MS no 479, Royal Society Library, pp. 1–33. For an approachable treatment of Ulloa’s voyage see Larrie D. Ferreiro, 1402 Measure of the Earth: The Enlightenment Expedition That Reshaped Our World, New York: Basic Books, 1403 2013; see also Francisco de Solano, Don Antonio de Ulloa: Paradigma del Marino Cientifico de la 1404 Ilustacion Española, Coimbra: Universidade de Coimbra, 1990, which has a nice description of Ulloa’s 1405 mineralogical work and discovery of platinum. 146 Folkes, letters and papers, op. cit. (145), pp. 30–31. 1406 147 Folkes, letters and papers, op. cit. (145), p. 1. Ulloa published his account in his Relación histórica del 1407 viaje a la América Meridional, 4 vols., Madrid, 1748. See de Solano, op. cit. (145), pp. 335–336, for a 1408 discussion of Ulloa’s editions. Taking Newton on tour 33

1409 official image. However, the 1739 portrait of Folkes commissioned from John 1410 Vanderbank very much shows him in the image of Newton, strikingly similar in iconog- 1411 raphy to Vanderbank portraits of the latter (Figure 6).148 Here we see Folkes’s self-fash- 1412 ioning as the heir apparent to the Royal Society presidency, something he achieved in 1413 1741 after Sloane’s death. Folkes’s journey to Italy was an expression of the motto 1414 scrawled on his travel diary, symbolic of who and what he would become, a natural phil- 1415 osopher who would manifest several elements of the Newtonian programme during his 1416 tenure as president of the Royal Society. 1417 Folkes’s diary thus demonstrates, importantly, that the impression among some his- 1418 torians that the eighteenth-century Royal Society was moribund has been mistaken. 1419 Sorrenson has noted that this unedifying impression stemmed from the belief that the 1420 Royal Society failed to match the standard that Newton had set in the Principia;it 1421 also stemmed from negative opinions voiced by the society’s critics, such as John Hill 1422 and from the popularity of Babbage’s Reflection on the Decline of Science in England 1423 (1830).149 It seems, however, that the Royal Society in the eighteenth century manifested 1424 considerable strengths in technological innovation, setting new standards in experimen- 1425 tal precision. 1426 And as Folkes’s journal shows, during his journey to Italy, and shortly after he 1427 returned, he was in the very centre of an intellectual network, brokering and furthering 1428 these aims. His diary also represented, as Feingold reminds us, the ‘confabulatory life’ of 1429 the scholar, the diffusion of scientific knowledge through informal discussion with col- 1430 leagues.150 Henry Guerlac has commented that ‘as historians of ideas we are happiest 1431 when we can navigate from the firm ground of one document to the next, and we are 1432 Q20 prone to forget how great a part travel, gossip and word-of-mouth have played in the 1433 diffusion of scientific knowledge, indeed of knowledge of all sorts’.151 In this manner, 1434 the journal of Folkes’s scientific peregrination demonstrates to us the parameters of 1435 Georgian antiquarian science and Newtonianism. 1436 1437 1438 1439 1440 1441 1442 1443 1444 148 The portrait’s provenance is by descent from the sitter with the family of the ffolkes Baronets at 1445 Hillington Hall in Norfolk, and was acquired by Christopher Foley FSA for his private collection. See Edmund Farrer (ed.), Portraits in Norfolk Houses, Norwich: Jarrold and Sons, 1929, vol. 1, pp. 245 et seq., 1446 sub Hillington Hall; John Kerslake, Early Georgian Portraits in the National Portrait Gallery, London: 1447 HMSO, 1977, p. 77 and 77 n., sub ‘Iconography’ of Martin Folkes. 1448 149 Sorrenson, op. cit. (123); see also George Rousseau, The Notorious John Hill: A Man Destroyed by 1449 Ambition in the Age of Celebrity, Bethlehem, PA: Lehigh University Press, 2012. 150 Mordechai Feingold, ‘Confabulatory life’, in P.D. Omodeo and K. Freidrich (eds.), Duncan Liddel 1450 (1561–1613): Networks of Polymathy and the Northern European Renaissance, Leiden, Brill, 2016, 1451 pp. 22–34. 1452 151 Henry Guerlac, Newton on the Continent, Ithaca, NY: Cornell University Press, 1981, p. 46.