James Gregory and the Reflecting Telescope

Ariotti P. E. , “Bonaventura Cavalieri, Marin Mersenne, and the reflecting telescope”, Isis, lxvi (1975), 303–21.

For a recent discussion of Short see Clarke T. N. Morrison-Low A. D. and Simpson A. D. C. , Brass & glass (Edinburgh, 1989), 1–6.

This account is drawn principally from Whiteside D. T. , “James Gregory” in Dictionary of scientific biography , ed. by Gillispie C. C. , v (New York, 1972), 524–30, supplemented by James Gregory tercentenary memorial volume, ed. by Turnbull H. W. (London, 1939).

The mathematical papers of Isaac Newton, iii: 1670–73, ed. by Whiteside D. T. (Cambridge, 1969), p. xiii.

Gregory J. , Optica promota, seu abdita radiorum reflexorum & refractorum mysteria, geometrice enucleata; cui subnectitur appendix, subtilissimorum astronomiae problematon resolutionem exhibens (London, 1663).

Turnbull (ed.), op. cit. (ref. 3), 454, translating Gregory , op. cit. (ref. 5), preface A3r.

Whiteside , op. cit. (ref. 3), 525.

Trans. from Gregory , op. cit. (ref. 5), preface A3r.

Whiteside , op. cit. (ref. 3), 525. The Marischal College Library copy of Risner's Opticae thesaurus, Alhezeni Arabis libri septem, nunc editi … item Vitellonis Thuringo-Poloni Libri X … (Basel, 1572) was bequeathed in 1613, and is now in Aberdeen University Library. The latter also has a copy in its Gregory Collection, but whether this copy was in James Gregory's hands at this early period cannot be said. I am grateful to the Librarian, Aberdeen University Library, for providing this information.

Turnbull (ed.), op. cit. (ref. 3), 455, translating Gregory , op. cit. (ref. 5), 13.

Propositions 37–43.

Gregory , op. cit. (ref. 5), 92–93. There is an intriguing possibility that Gregory may have encountered the designs by Mersenne for catoptric telescopes. These were published in a number of Mersenne's works including the Harmonica (Paris, 1635), of which there was a copy in Marischal College Library (but the provenance is unknown), and in the Cogita physico-mathematica (Paris, 1644), a copy of which was in the Gregory family collection (although again its acquisition date is unknown). Both are now in Aberdeen University Library. I am grateful to the Librarian, Aberdeen University Library for these details.

Trans. from Gregory , op. cit. (ref. 5), 93. Although Gregory described the mirrors as being co-focal, he had the secondary placed “in” and not “near” the focus of the primary. Turnbull noted that Gregory corrected this in his annotated copy, now in the Library at the University of St Andrews: Turnbull , op. cit. (ref. 3), 456.

Trans. from Gregory , op. cit. (ref. 5), 95.

Idem.

Idem. The Epilogus then concludes with the words “Hic itur ad astra”. I am indebted to the late Dr Robin Schlapp for checking my translation of this passage.

Whiteside , op. cit. (ref. 3), 524. There appears to be no direct evidence for Gregory's departure in 1662, but the book could not have been printed, so carefully proof-read and bound by mid-February if Gregory had not been in London from at least the end of the year. I am grateful to Professor D. T. Whiteside for his comments on this aspect.

See Martin D. C. , “Sir Robert Moray, F.R.S.”, in The Royal Society: Its origins and founders, ed. by Hartley H. (London, 1960), 239–50.

Oeuvres complètes de Christiaan Huygens, iv: Correspondence 1662–63 (The Hague, 1891), 318, 330.

On the Gordons see particularly Stone J. C. , “Robert Gordon of Straloch: Cartographer or chorographer?”, Northern Scotland, iv (1981), 7–22.

Simpson A. D. C. , “Sir Robert Sibbald”, in Royal College of Physicians of Edinburgh Tercentenary Congress, ed. by Passmore R. (Edinburgh, 1982), 59–91, p. 82.

See Youngson A. J. , “Alexander Bruce, F.R.S., second Earl of Kincardine (1629–1681)”, in Hartley (ed.), op. cit. (ref. 18), 251–8. The date of death of the first Earl is normally given merely as 1662: However, it is clear from his correspondence and from the records of the Privy Council that he only assumed the title between March and July 1663. On masonic links between Bruce and Moray, and on Moray's contacts with the operative masons' craft guild in Maastricht in 1659, see Stevenson David , The origins of Freemasonry: Scotland's century, 1590–1710 (Cambridge, 1988), 171–7.

Ibid., 252.

Record of the Privy Council of Scotland, 3rd ser., i: 1661–64 (Edinburgh, 1905), 8. He was present regularly at meetings, but there was a gap in attendance between August 1662 and June 1663.

Bruce to Huygens , 29 January 1664: Youngson , op. cit. (ref. 22), 253–4.

Leopold J. H. , “Clockmaking in Britain and the Netherlands”, Notes and records of the Royal Society of London, xliii (1989), 155–65, p. 159, where the clockmaker is identified as Severijn Oosterwijck of The Hague. The timepieces, which had 7-inch pendulums, are referred to in the correspondence as Bruce's, which implies that he had purchased them: Huygens to his brother, 28 December (N.S.) 1662, and Bruce to Huygens , 2 January 1663: Huygens , op. cit. (ref. 19), 285, 290.

Results of the tests between April and September 1663 on a voyage to Lisbon are printed in ibid., 446–51.

Huygens's correspondence had misled Moray into thinking that he would leave for Paris earlier. When he heard at the end of March that Huygens was still at the Hague he wrote there to say that he had sent a letter to Paris by the hand of a young man who had instructions to leave it with Huygens's father (then resident in Paris) if Huygens had not yet arrived. This young man also had a present to give him of “a book of which he is the author, called Optica promota, which treats Dioptrics and Astronomy, and of which I wish to say nothing so that you may reach a judgement in full”: Trans. from letter of Moray to Huygens , 27 March 1663, ibid. , 330. The letter which Gregory was carrying was written by Moray on 19 February, so we may perhaps assume that the Optica promota was published in February and that Gregory left for Paris towards the end of the month. Huygens arrived in Paris on 24 March.

Huygens's opinion was given in a letter which Moray did not receive. The book was acknowledged in another of 22 May, but his comments were reserved until he met Moray about two weeks later at the start of a stay in London: Huygens , op. cit. (ref. 19), 351, letter of Huygens to Moray, 1 June (N.S.) 1663. By this time Bruce had returned to Scotland — he attended a Privy Council meeting in Edinburgh on 2 June 1663.

Enriques F. , “James Gregory e il suo soggiorno in Italia”, in Turnbull (ed.), op. cit. (ref. 3), 465–8, p. 465; Whiteside , op. cit. (ref. 3), 524.

Whiteside , op. cit. (ref. 3), 526.

Huygens was sent a copy on 28 September 1667: Oeuvres complètes de Christiaan Huygens, vi: Correspondence 1666–69 (The Hague, 1895), 154.

For Collins see Whiteside D. T. , “John Collins”, in Dictionary of scientific biography, ed. by Gillispie C. C. , iii (New York, 1971), 348–9.

For example, in Stewart A. C. , The academic Gregories (Edinburgh, 1901), 28, followed by Turnbull (ed.), op. cit. (ref. 3), 3.

Turnbull (ed.), op. cit. (ref. 3), 47: Draft letter of Collins to Gregory. The inclusion of a passage from Isaac Barrow in the letter suggests it was dated after 6 March 1668, which was the date of Barrow's letter to Collins. The letter, which had an enclosure, gives the impression of being in part a repeat of an opening letter from Collins, and it was this earlier letter that Gregory answered on 16 March 1668 (Turnbull did not change the occasional Gregorian ‘New Style’ dates of manuscripts), shortly before leaving Padua. Sion College was founded in London in 1623 as a college and almshouse, and had a substantial library.

Ibid., 45: Collins to Gregory , undated draft, early 1668.

Ibid., 55: Collins to Gregory , 30 December 1668.

Morrison Paul G. , Index of printers, publishers and booksellers in Donald Wing's Short-title Catalogue … 1641–1700 (Charlottesville, Virginia, 1955), entries G1912 (excudebat J. Hayes pro S. Thomson) and H2612 (by J. H. for Sam Thomson). Hayes H.J. and Hayes John entries cease after the ruin of his business in the fire of 1666. On Hooke's volume see Keynes G. , A bibliography of Robert Hooke (Oxford, 1960), 6–8.

Alumni Oxoniensis … 1500–1714, ed. by Foster J. (Oxford and London, 1892), 1477.

Ibid., 556; Plomer H. R. , A dictionary of the booksellers and printers who were at work in England, Scotland and Ireland from 1641 to 1667 (London, 1907), 81, 179.

Turnbull (ed.), op. cit. (ref. 3), 240: Gregory to Collins , 23 September 1672.

Birch T. , The history of the Royal Society of London (London, 1756–57), i, 20: 10 April 1661.

Simpson A. D. C. , “Robert Hooke and practical optics: Technical support at a scientific frontier”, in Robert Hooke: New studies, ed. by Hunter M. and Schaffer S. (Woodbridge, Suffolk, 1989), 33–61: On John Cock see p. 43.

The correspondence of Henry Oldenburg , ed. by Hall A. R. and Hall M. B. , ii: 1663–65 (Madison, Wisconsin, 1966), 560–641 passim.

A collection of letters illustrative of the progress of science in England, ed. by Halliwell J. O. (London, 1841), 72–74.

This discussion of Reeve is taken from Simpson A. D. C. , “Richard Reeve — the ‘English Campani’ — and the origins of the London telescope-making tradition”, Vistas in astronomy, xxviii (1985), 357–65, and the more extended account in Simpson , op. cit. (ref. 43).

Ibid., 39, n. 20.

Ibid., 45.

The date must refer to Hooke's experiments, rather than to the original work for Gregory. This reference is apparently the cause of the confusion about the date of Gregory's departure for the Continent, which is sometimes claimed to have been in 1664: See, for example The correspondence of Isaac Newton, i: 1661–75, ed. by Turnbull H. W. (Cambridge 1959), 115, n. 4, and King H. C. , The history of the telescope (London, 1955), 71. It may also have led Professor Eva Taylor to claim (incorrectly) that two telescopes were made, in 1663 and 1668: Taylor E. G. R. , The mathematical practitioners of Tudor and Stuart England 1485–1714 (Cambridge, 1954), 246.

Correspondence of Newton, i (ref. 49), 154: Newton to Oldenburg, 4 May 1672.

Hooke's comment that the parabola was more difficult to describe than the hyperbola or ellipse related to geometrical constructions that were potentially useful in the grinding of conic surfaces: For example the property of generating a hyperboloid by a line (i.e. cutting edge) skew to the conoid's axis had been proposed by Wren. Hooke was preoccupied with the need to be able to produce the figure mechanically.

Correspondence of Newton, i (ref. 49), 279: Gregory to Collins , 13 May 1673. From the sense of this and of the letter it answers, the trial is that of Gregory and not Hooke. Gregory understood the “trial” of the instrument as the attempt to put the design into practice and not the subsequent experimentation with the components to test their effect. Newton initially assumed that Hooke had been involved in Gregory's original construction attempt, and therefore assumed that careful efforts to produce non-spherical surfaces would have been made. Gregory, aware that Hooke had not been involved, made comments only on his own work, and began to resent Newton's pedantic interpretation of his earlier published comment which was having the effect of denigrating his instrument. The original mirrors are unlikely to have survived until this time, and had probably been seized with Reeve's goods in late 1664; Reeve's death, four years after this, prevented him contributing to the debate: Simpson , “Reeve” (ref. 46).

Simpson , op. cit. (ref. 43), 44. It seems very likely that the work of John Cock for the Society in 1660–61, referred to above in connection with Moray's committee, was also directed towards aspheric lenses. Cock was also associated with John Beale's attempts to “perfect” lenses in 1659–60: Oldenburg to Hartlib , 23 July 1659, and Oldenburg to Beale , 4 September 1660, The correspondence of Henry Oldenburg , ed. by Hall A. R. and Hall M. B. , i: 1641–62 (Madison, Wisconsin, 1965), 288, 329.

Hooke stated that Reeve's first 60-ft lens was made in 1662: Oldenburg to Auzout, 23 July 1665, Correspondence of Oldenburg, ii (ref. 44), 442.

Gregory , op. cit. (ref. 5), preface A3r; Turnbull (ed.), op. cit. (ref. 3), 454. Subsequent detailed study of Descartes after his arrival in London caused Gregory to revise his Optica promota, but although part of the manuscript for this survives and Gregory at one time intended to publish it, yet it was never printed: Turnbull (ed.), op. cit. (ref. 3), 41–43, 55, 118, 262, 458–9; Whiteside , op. cit. (ref. 3), 526.

Correspondence of Newton, i (ref. 49), 240: Gregory to Collins , 23 September 1672. Newton later came to the conclusion that the trial had been only of spherical mirrors, but Gregory was not prepared to confirm this: ibid., 271: Newton to Collins , 9 April 1673.

The radius of curvature was the same as that of the faces of the 6-ft objective lenses which Reeve was offering commercially at the time: Court T. H. and von Rohr M. , “New knowledge of old telescopes”, Transactions of the Optical Society, xxxii (1930–31), 113–22, p. 121.

Gregory provided the only evidence that Cock was working for Reeve at this period in his letter to Collins of 7 March 1673: Correspondence of Newton, i (ref. 49), 259.

Ibid., 240: Gregory to Collins , 23 September 1672.

Ibid., 259: Gregory to Collins , 7 March 1673. The primary mirror had received only a preliminary polish with “a cloath and puttie”.

Ibid., 240.

Ibid.

Ibid. This has been noted, but without comment, by Desaguliers J. T. , “Appendix … containing, an account of the reflecting telescope; … with original letters which passed between Sir Isaac Newton and Dr. James Gregory …”, in Gregory D. , Elements of catoptrics and dioptrics, translated … by William Browne (2nd edition, London, 1735), 218–88, p. 212.

King , op. cit. (ref. 49), 71.

This is assumed for example by Desaguliers , op. cit. (ref. 63), 212; Pringle J. , A discourse on the invention and improvements of the reflecting telescope (London, 1778), 7; Danjon A. and Couder A. , Lunettes et telescopes (Paris, 1935), 611; Turnbull (ed.), op. cit. (ref. 3), 3; King H. C. , “Early development of the reflecting telescope”, The refractionist, xxviii (1939), 340–55, p. 341; King , op. cit. (ref. 49), 71; Bechler Z. , “‘A less agreeable matter’: The disagreeable case of Newton and achromatic refraction”, The British journal for the history of science, viii (1975), 102–26, p. 104.

Hooke's work is assessed in Simpson , op. cit. (ref. 43).