1 Bradley, J., ‘A Letter to Dr. Edmund Halley, Astrom. Reg & c. giving an account of a new-discovered Motion of the Fixed Stars’, Philosophical Transactions (1729), 35, 637–61.CrossRefGoogle Scholar

2 J. Bradley, The Kew Observation Book K14, Bradley MS 14; and idem, Observations on the Fixed Stars made at Wanstead from 1727 to 1747, Bradley MS 15, Department of Western Manuscripts, Bodleian Library, Oxford.

3 J. Bradley, Drafts of Papers by James Bradley on Aberration, Bradley MS 20*, Department of Western Manuscripts, Bodleian Library, Oxford. First version, fols. 1r–2v and fols. 15r–16v. Second version, fols. 3r–14r and 17r–17v. Third version, fols. 18r–30v. Transcribed and edited by John Fisher. Here see especially third version, fols. 18r–30v. None of these versions have been published except as appendices to my M.Sc. dissertation, ‘James Bradley and the new discovered motion: the origins, development and reification of James Bradley's hypothesis of the new discovered motion of the fixed stars’, Imperial College, London University, 1994. There is another version sent to Edmond Halley for presentation to the Royal Society at meetings on 9 and 16 January 1729. This was published in Philosophical Transactions.

4 Wanstead was the site of the seat of the Child family, major shareholders of the English East India Company. Wanstead House and its extensive grounds had been bought by Sir Josiah Child and the estate was inherited by Sir Richard Child in 1699. In 1720 Sir Richard commissioned Colen Campbell, the author of the ‘British Vitruvius’, to build the vast Palladian mansion, a house that dominated its surrounding environs. James Pound had been given his lucrative living by Sir Richard after his return from the Indies, where he was in the service of the East India Company.

5 Isaac Newton, Philosophiae Naturalis Principia Mathematica, 3rd edn, enlarged and revised, 1726. The observations made by Pound on ‘the proportion of the diameters of Jupiter to each other’ are referred to by Isaac Newton in his preface to the third edition which had been supervised by Henry Pemberton.

6 Isaac Newton, The Principia: Mathematical Principles of Natural Philosophy (a new translation by I. Bernard Cohen and A. Whitman assisted by J. Budenz), London, 1999, 797–8.

7 The problem was discussed by William Molyneux and John Locke. On 7 July 1688 Molyneux sent a letter to Locke in which he proposed a problem that is still discussed by contemporary philosophers. Molyneux asked whether a man born blind who has learnt to distinguish and name a globe and a cube by touch would be able to distinguish and name these objects simply by sight, once he had been enabled to see.

8 For Bossiney from 1715 to 1722, for St Mawes from 1726 to 1727 and for Exeter from 1727 until his early demise on 13 April 1728. From 1727 he also served as an MP for Dublin University in the Irish Parliament.

9 Hadley invented a practical reflector that was used by Pound and Bradley in various trials at Wanstead. In his will Bradley left the instrument to his sister Rebecca. Bradley undertook sea trials in 1732 of a nautical octant constructed by Hadley. It was the forerunner of the modern sextant.

10 Graham married Tompion's niece.

11 This was the first ‘orrery’, the term generally applied to such clockwork planetaria.

12 A diagram of the zenith sector that Graham constructed for Bradley and suspended at Wanstead can be found in Figure 2.

13 On 23 June 1708 Sir Ralph Dutton's son John took out an ‘indenture of assignment’ controlling his expenditure and by 1709 he was forced to take over control of the estate, granting an allowance for his father until he died in 1721.

14 Latitudinarianism was a theological stance which accepted that human reason was a sufficient guide when combined with the Holy Spirit for the determination of truth in doctrinal contests, and therefore that legal and doctrinal rulings that constrain reason and the freedom of the believer were neither necessary nor salutary. At the time, their position was referred to as Low Church.

15 The death of Pound at the age of 55 was very sudden and entirely unexpected. He was very active, wealthy and well connected but died so suddenly that he had not made provision for the possibility of his death. Dying intestate left his nephew James Bradley in a difficult financial position, the estate being divided between his widow Elizabeth Pound and his daughter Sarah from an earlier marriage. That his death was sudden can be judged from his account book, which reveals that he was very active right up to the time of his death. He was in London on business just two days before his demise.

16 It was the parish of Llanddewi Velfrey. Bradley had obtained the living at Bridstow near Ross on Wye after his ordination by the bishop of Hereford, Dr Benjamin Hoadly, who also appointed him his personal chaplain and secretary. Hoadly was a long-standing associate and friend of Pound. Both were FRSs. Bradley relinquished all of his church preferments when he was elected the Savilian Professor of Astronomy at Oxford on 31 October 1721, a condition of the office.

17 The measurement of variations in right ascension was the method chosen by the Italian astronomer Eustachio Manfredi from 1707 to 1728 at Bologna.

18 This was the method devised by Christopher Wren and Robert Hooke sometime during the 1650s.

19 S. P. Rigaud, Memoirs of Bradley, Oxford, 1832, 16.

20 Rigaud, op. cit. (19), 16.

21 Bradley, op. cit. (1), 638.

22 S. Molyneux, ‘A description of an instrument set up at Kew, in Surrey, for investigating the annual parallax of the fixed stars, with an account of the observations made therewith’, in J. Bradley, Miscellaneous Works and Correspondence of James Bradley, Oxford, 1832, 109–10.

23 Molyneux. op. cit. (22), 109.

24 There can be little doubt that Halley's observational practice was in no way comparable to the remarkable skills evidenced by Bradley in all of his mature work. There is a very revealing passage which was included in the Miscellaneous Works and Correspondence of James Bradley and remarked upon by Rigaud. In the ‘Observations of the fixed stars made at Wansted in Essex by J. Bradley’ (Bradley, op. cit. (22), 208), Bradley writes, ‘Dr. Halley observed Capella; The star fluttered much, and he said as it went out it appeared to be more southerly in reality than the thread; he therefore fancied from this observation that the direction of the thread was not right; but as all the other stars going out appear on the other side of the wire, this appearance must be owing to his not being able to bisect the star at the cross, because of its fluttering.’ With reference to this passage Rigaud commented, ‘Though Halley's was certainly a very powerful mind, it was not always free from error; for he not only had too much contempt for what appeared to him to be trifles, but he was often too rapid in drawing his conclusions.’

25 In his account Bradley states he made his observation on 20 December but in the Kew Observation Book it is recorded as being on 21 December. Civil dates are reckoned from midnight but astronomical dates from noon. γ Draconis having passed conjunction it now passed through the meridian after noon on 20 December according to the civil date and on 21 December according to the astronomical calendar.

26 The monument commemorating Bradley's ‘discovery’ of the aberration of light is located within the grounds of the Royal Botanical Gardens in Kew.

27 Bradley, op. cit. (3), fol. 18r.

28 R. Burnham Jnr., Burnham's Celestial Handbook: An Observer's Guide to the Universe beyond the Solar System, New York, 1978, 865, states that the object star γ Draconis has a magnitude of 2.22.

29 An astronomical unit (AU) is the mean distance from the centre of the Sun to the centre of the Earth in its orbit around the Sun. It is the fundamental baseline for all parallactic calculations.

30 Newton, op. cit. (6), Book 3, Proposition 42, 935.

31 Halley, E., ‘Considerations on the Change of the Latitudes of some of the principal fixt Stars’, Philosophical Transactions (1719), 30, 736–8.CrossRefGoogle Scholar

32 In 1712 Halley had edited the Greek text of Ptolemy's star catalogue. See E. Halley, Geographiae Veteris Scriptores Graeci Minores, vol. 3, Oxford, 1712.

33 On 6 and 9 July, 6 August and 21 October 1669.

34 Newton personally presented a special Moroccan bound copy of the third edition of the Principia to Bradley in gratitude for his work and support in its preparation.

35 He was a lecturer and later a reader in experimental philosophy from 1729 until 1760. He presented three sets of lectures each year. They are an exposition of Newtonian natural philosophy.

36 Bradley, op. cit. (3), fol. 18r.

37 Newton, op. cit. (6), 819.

38 Allan Chapman records this abandonment. He writes, ‘Then suddenly, Pound seemed to lose interest, and, in spite of constant solicitations from Hodgson and Crosthwait he produced no more sheets. It was suspected that Newton and Halley had been “tampering with him in order to retard the work”.’ A. Chapman, The Preface to John Flamsteed's ‘Historia Coelestis Britannica’, National Maritime Museum, Maritime Monographs and Reports, No. 52, 1982, 12.

39 Inexplicable because the star appeared to change its declination three months out of phase of the prediction of parallactic theory; counterintuitive because the star moved in the same direction as the Earth and not in the opposite direction as predicted by the theory of annual parallax.

40 The shift away from an explanation based on a combination of observational and instrumental errors was probably a gradual process, never entirely abandoned until Bradley was able to make multiple confirmations of the phenomenon over a wide range of ecliptical longitudes and latitudes. By March 1726 Molyneux, Graham and Bradley recognized that they were almost certainly observing a new natural phenomenon.

41 Bradley, op. cit. (3), fol. 19v.

42 Bradley, op. cit. (3), fols. 19v–20r.

43 Bradley was very cautious in all of his work and this caution extended to the possibility that there may have remained some instrumental, observational or systemic error somehow still overlooked.

44 Bradley, op. cit. (3), fol. 20r.

45 Although there had been a major technical revolution in instrumental accuracy and precision between 1686 and 1725 the expected motion of such an annual nutation was expected to be at the very limits of instrumental resolution, far less than the observed motions of the inexplicable phenomenon the partners were presently observing.

46 With annual variations of about forty seconds of arc per year.

47 W. Tirion et al., Uranometria 2000.0: Volume 1 – The Northern Hemisphere to – 6°, Richmond, VA, 1987. I have observed the star easily at night but it is very difficult to locate it as it passes near the zenith during the day. Bradley was able to observe this star quite close to midnight during the early months of 1726. The star is located in Flamsteed's British Catalogue.

48 Bradley, op. cit. (3), fol. 20r.

49 S. Molyneux, ‘Observations at Kew’, in Bradley, op. cit. (22), 141–8.

50 Conduitt was married to Newton's niece, Mary Barton.

51 Bradley and Graham remained close friends and commonly partners for many years. Bradley often referred his work to Graham up to the 1740s.

52 I say ‘eagerly’ because it was both premature and controversial.

53 J. Conduitt, ‘Memorabilia’, King's College Library, Cambridge, Keynes MS 130.5; added emphasis.

54 Molyneux collapsed during a debate in the House of Commons a few days before his death.

55 Stephen Peter Rigaud was Bradley's first biographer. A permanent debt is owed to his diligence and care when he gathered and published most of Bradley's major work and correspondence for much had already gone astray. He was able to save many documents which were carelessly scattered in various locations in Oxford. The Bradley papers came into the possession of the University of Oxford in 1776.

56 Rigaud, op. cit. (19), 20.

57 The archives of William and Samuel Molyneux are located at Southampton Records Office.

58 Molyneux, op. cit. (49), 141–8.

59 In 1992 I placed a ring around a two-inch refractor so that only the middle inch could be used (in a similar manner to the method used by Bradley and his contemporaries). In my experiment the instrument (of simple construction) had a focal length of less than five feet and I found the location of 35 Camelopardalis impossible in the full glare of a bright summer's day. As the instruments used by Bradley possessed much longer focal lengths of up to nearly 25 feet it may have been possible for such an acute observer to have observed it nevertheless. It may well be an interesting experiment to perform in the future. If 35 Camelopardalis was observed as a control star it could only have been observed easily during the winter months when it passed through the meridian at night.

60 Bradley, op. cit. (3), fol. 20r.

61 Bradley, op. cit. (3), fol. 22r. Bradley simply wrote, ‘Then I considered what refraction might do, here also nothing satisfactory occurred’.

62 Newton, op. cit. (6), Book 2, Section 1, Proposition 4, Problem 2, reveals that the amount of resistance encountered in a fluid medium to create such an effect would probably lead to the Earth and the other planets gradually spiralling into the Sun.

63 Rigaud, op. cit. (19), 21.

64 Neither of the dates of the two missing documents can be reconciled with the evidences offered by the Kew Observation Book and we can be sure that the nutation must have been abandoned before March 1726. It is difficult to conceive of a test for the refraction hypothesis by simply observing two stars, one of which was impossible to observe during the daytime.

65 Rigaud, op. cit. (19), 22.

66 Rigaud, op. cit. (19), 22.

67 Bradley, op. cit. (3), fol. 20v.

68 J. Bradley, ‘Memoranda respecting the instrument at Wanstead’, in Bradley, op. cit. (22), 194.

69 Rigaud, op. cit. (19), 74.

70 Elizabeth Pound lived with Bradley until her final illness in 1737, even moving to Oxford with him when he transferred his main residence from Wanstead to Oxford in 1732. Bradley did not marry until after Elizabeth died. He was forbidden by Georgian family law to marry his uncle's widow.

71 Bradley, op. cit. (22), 194–5.

72 It is presently displayed on the west wall of the transit house at the Old Royal Greenwich Observatory.

73 Bradley, op. cit. (3), 21r.

74 Bradley, ‘Reduction of the Wansted Observations’, in Bradley op. cit. (22), 302.

75 Bradley, op. cit. (22), 303.

76 Bradley, op. cit. (22), 303.

77 Bradley, op. cit. (22), 303.

78 Bradley, op. cit. (3), fol. 21v.

79 This is the measure of Bradley's achievement. Although astronomers had been observing many different anomalous or unaccountable motions for decades no one had succeeded in isolating them or explaining them in terms of anything but annual parallax.

80 Bradley, op. cit. (3), fol. 23v.

81 The following passage attempts to clarify the geometry of the ‘new-discovered motion’. It explicitly reveals the shape of the inferred ellipse according to the ecliptical latitude of the star. As such it describes the motion of any fixed object in accordance with the law of the ‘new-discovered motion’.

82 Bradley, op. cit. (3), fol. 24r.

83 In 1711 he moved from the parental home in Sherborne in Gloucestershire to his maternal uncle's home in Wanstead in Essex. His earliest recorded observations date from 1712.

84 Halley quickly adopted Bradley as a protégé for he soon recognized that his abilities were outstanding.

85 This apparent lack of explanation is in my opinion the main reason why apocryphal accounts such as that written by Thomas Thomson gained acceptance. The passage was written eighty years after the events described and forty-six years after the death of Bradley. The account offered by Bradley is adequate, provided his working practice is apprehended. Both Arthur Berry, when he researched Bradley's work in 1898, and I have utterly failed to find any documentary evidence to support Thomson's account.

86 T. Thomson, History of the Royal Society, London, 1808.

87 The method of observing the eclipses of Jupiter as a way of determining the longitude at sea was eventually abandoned in favour of the lunar method. Halley concentrated on the development of his lunar theory. The Jovian method was impractical on a pitching ship at sea.

88 In 1738 Bevis set up his own observatory at Stoke Newington, from where he made observations for his own star atlas, Uranographia Britannica, which he completed in 1750.

89 By 1753 it appears that Bevis had moved his domicile to Clerkenwell.

90 Bradley, op. cit. (3), fol. 24r.

91 The two stars he refers to are γ Draconis and η Ursae Majoris. In his account he compares the observations of these two stars with the predictions of the law of the new-discovered motion.

92 Bradley, op. cit. (3), fol. 29r.

93 In modern parlance this is the equivalent of an annual parallax of 0.500″. Modern practice determines annual parallax from the baseline of an astronomical unit, the mean radius of the Earth's orbit. In Bradley's day it was calculated from a baseline equal to the mean axis major, the mean diameter of the Earth's orbit.

94 Although most astronomers were confident that the heliocentric model was valid there remained a persistent minority who still upheld geocentric or geostatic models. These included Jacques Cassini, who maintained his father's reticence in accepting the Copernican thesis. Jacques Cassini's cousin Jacques Maraldi was definitely opposed to the heliocentric model. Based, like Cassini, in Paris, Maraldi was in correspondence with another notable geocentrically inclined astronomer, Eustachio Manfredi in Bologna.

95 Bradley, op. cit. (3), fol. 29r.

96 Although Manfredi observed many similar motions in right ascension and used them as evidence to object to the Copernican theory.

97 See Williams, M., ‘James Bradley and the eighteenth century “gap” in attempts to measure annual stellar parallax’, Notes and Records of the Royal Society of London (1982), 37, 83–100.CrossRefGoogle Scholar

98 Unknown to Bradley, both Jeremiah Horrocks and William Crabtree had in 1638 observed how, in a darkened-limb lunar occultation, star points vanished instantaneously when viewed telescopically.

99 Bradley, op. cit. (3), fol. 29v.

100 This is testified by the inclusion of a suffix, giving evidence of Flamsteed's observations in support of his hypothesis. In the third unpublished version, which I am certain was Bradley's intended final version, this data is included in the body of the paper.

101 Bradley, op. cit. (1), 637–61.

102 The third, unpublished, version is dated 5 January. The preliminary version was read at the Royal Society from 9 January before Bradley could finish his intended final, more considered, version. The date of the published paper cannot be confirmed for there is no evidence that it was retained after it was printed.

103 E. Manfredi, De annuis inerrantium stellarum aberrationibus, Bologna, 1729.

104 It is very difficult to determine the real extent of Manfredi's commitment to a geocentric or geostatic cosmological position. A very interesting paper by Gualandi, A. and Bònoli, F., ‘The search for stellar parallaxes and the discovery of the aberration of light: the observational proofs of the Earth's revolution, Eustachio Manfredi and the Bologna case’, Journal of the History of Astronomy (2009), 11, 155–72CrossRefGoogle Scholar, reveals the difficulties under which Manfredi worked. They write, ‘With De annuis Manfredi had ventured into the troublesome terrain of the World System’. As the authors stress, it was difficult in spite of the problems raised by ‘the observed shifts in the positions of the stars’ to give credence to any open acceptance of the Copernican system ‘in territories such as Bologna, which were directly governed by the Holy See’. All these quotations at 162.

105 Manfredi, op. cit. (103), 1–2. The Latin reads, ‘Sunt tamen nonnulli, qui cum illas Stellarum evagationes statis anni temporibus recurrere animadvertant, minimè dubitandum existement quin ea res ad annuum, quem Telluri cum Copernico tribuunt, motum pertineat, atque adeo vel hoc ipso indicio detectum, demonstratumque verum Mundi systema deprædicent, in quo tamen decipi proclive est, labante Copernicano Systemate unà cum argumentis, quibus illi suffultum arbitrantur, id quod in hoc ipso opera demonstraturum me esse confide.’ Translated into English by David Simonson.

106 Gualandi and Bònoni, op. cit. (104), 162.

107 Which probably date from late 1729 or sometime early in 1730 as evidenced by the ink and paper used in comparison to dated letters.

108 Bradley, op. cit. (3), fols. 56 and 60.

109 Manfredi, op. cit. (103), Caput IX, Sections 154–5, 69. The Latin reads, ‘ … sateri cogimur ambiguum esse judicium, utri Stellarum, illine, cujus aberrations quaerimus, anne alteri, cum qua hanc ipsam comparamus, aut forte utrique, error fit tribuendus. 155. In hac dubietate nihil fatius occurrit, quam si duas, pluresue ex inerrantibus Stellis seligamus, quarum intervalla adventus ad meridianum plurimis observationibus, iisque exquisitis, ac per diverto Stellarum numero multis earum, Stellæ illius tempora resenius, cujus aberrationem investigare, ac mensuris praesinire suscepimus.’

110 Bradley, op. cit. (1), 646.

111 Though stars on the plane of the ecliptic would only vary in right ascension and there would be no observed change in declination.

112 Bradley, op. cit. (3), fol. 60v.

113 Bradley, op. cit. (2), fol. 56r.

114 Maupertuis to Bradley, Paris, 27 September 1737, in Bradley op. cit. (22), 406.

115 Not to be confused with the annual solar-induced nutation first proposed as a hypothesis in 1726 by the partners when observing the aberration of light in Kew.

116 Bradley to Maupertuis, Oxford, 27 October 1737, in Bradley, op. cit. (22), 409. This motion of 9″ from the mean was finally observed over a period equal to a complete precession of the nodes of the lunar orbit around the Earth, a period in excess of eighteen years.

117 The chief of which were an attempt to confirm an annual parallax of 30″, an annual nutation of up to 40″ and a motion due to the refraction of the atmosphere due to the Earth moving through a dense medium, all of which were inimical to Newtonian natural philosophy.

118 Conduitt, op. cit. (53), MS 130.5. Conduitt recalls that Newton's response to the news was both magnanimous and generous, for he reports Newton saying, ‘there is no arguing against facts and experiments’.

119 Berkeley was Molyneux's tutor at Trinity College.

120 Pound had been a wealthy man with two lucrative church livings at Wanstead and Burstow, a private income independent of these sources and a large dowry that came with his second wife Elizabeth who was the sister of Matthew Wymondsold, a wealthy speculator in South Sea stock who had sold all of his holdings one day before the bubble burst. On his death, Bradley was left with no support other than his income from the Savilian professorship.

121 These included the Parker family (George Parker, the second Earl of Macclesfield, later became his strongest friend and patron), the Hoadly family (Dr Benjamin Hoadly had ordained Bradley as a priest) and other supporters such as Martin Foulkes, a future President of the Royal Society, who was a nephew of William Wake, Archbishop of Canterbury. Later, Bradley acquired many more supporters, including George II.

122 Molyneux collapsed during a debate in the House of Commons and died a few days later on 13 April 1728.

123 Manfredi died in 1739, and only when Pope Benedict XIV issued the decree suspending the placing of texts ‘docents immobilatem Solis et mobilatem Terrae’ on the Index librorum prohibitorum on 16 April 1757 were Catholic astronomers within the papal domains free to openly espouse heliocentric cosmological models.

124 Some Tories and High Church Anglicans thought Newton's natural philosophy was atheistic and many supported various biblically based cosmologies such as Hutchinsonianism.

125 From 1729 to 1760 inclusive Bradley gave three and later two courses of lectures each academic year. These were always well attended, with about fifty or sixty students enrolled for each course, each paying a fee of two or three guineas.

126 F. W. Bessel, Fundamenta Astronomiae pro anno MDCCLV deducta ex observationibus viri incomparabilis James Bradley in specula Grenovicensi per annos 1750–1762 institutis, Königsberg, 1818.

127 Bradley, op. cit. (3), fol. 29r.