The Observatory and the Quadrant in Eighteenth-Century Europe

Writing of the present study was in part prompted by the examination of several quadrants in the course of surveys, undertaken with Françoise la Guet Tully, of historical instruments surviving in French observatories. These surveys were carried out as part of the Inventaire Nationale de la Patrimoine Astronomique, an inter-ministerial project co-sponsored by the Ministère de la Recherche (Mission de la Culture et de l'Information Scientifiques et Techniques et des Musées), and the Ministère de la Culture et de la Communication (Direction de l'Architecture et du Patrimoine). The results are available electronically in the data base Palissy, and on paper at the Centre de Documentation of the Musée des Arts et Métiers, Paris.

For Flamsteed and Hooke see Howse Derek , Greenwich Observatory, iii: He buildings & instruments (London, 1975), 17–19. The quadrant made by Blaeu for Willibrod Snel is now in the Museum Boerhaave, Leiden. Instruments made by Elias Allen are in the Museum of the History of Science, Oxford and are described by Gunther R. T. , “The first observatory instruments of the Savilian Professors at Oxford”, The observatory, lx (1937), 190–7. Tycho's own description of his instruments is Astronomiæ instauratæ mechanica (Wandesburg, 1598), which is conveniently translated in Hans Ræder, Elis Strömgren and Bengt Strömgren, Tycho Brake's description of his instruments and scientific work (Copenhagen, 1946). For Islamic instruments see Aydin Sayih, The observatory in Islam and its place in the general history of the observatory (Publications of the Turkish Historical Society, ser. vii, no. 38; Ankara, 1960), s.v. index. Many aspects of developments in Europe are treated in Chapman Allan , Dividing the circle: The develoment of critical angular measurement in astronomy 1500–1850 (Chichester, 1990).

For a description see Howse, op. cit. (ref. 2), 21–24.

See Bennett J. A. , “The English quadrant in Europe: Instruments and the growth of consensus in practical astronomy”. Journal for the history of astronomy, xxiii (1992), 1–14.

This point is established, and the nature and use of the quadrants fully described, by Danielle Fauque, “Un instrument essentiel de l'expédition pour la mesure de la Terre: Le quart de cercle mobile”, in Lacombe Henri and Costabel Pierre , La figure de la Terre du XVIIIe siècle à l'ère spatiale (Paris, 1988), 209–21.

“Le quart-de-cercle mobile est de tous les instrumens d'Astronomie, celui dont l'usage est le plus ancien, le plus général, le plus indispensable, le plus commode”, Jérôme de Lalande, Astronomie (2 vols, Paris, 1764), ii, 843, para 1827 (2nd edn, 4 vols, Paris, 1771, ii, 743, para 2311). Cf. i, 788, para 1656 where Lalande adds that the portable quadrant is the instrument to be preferred whenever possible.

Bennett , op. cit. (ref. 4), 4.

Lalande , Astronomie (ref. 6), ii, 757: “plusieurs sextans de 6 pieds de rayon pour différens Observatoires de l'Europe; mais ce sont des instrumens mobiles…, à deux lunettes, faits sur le principe du quart-de-cercle de la figure 149”.

Gassendi possesed two portable quadrants respectively of 3 ½ ft and 2ft, and a 5ft mural quadrant. See the list of his apparatus with source references in Anthony Turner with Gomez Nadine , Pierre Gassendi, explorateur des sciences (Digne-les-Bains, 1992), 140, no. 167.

Lalande , Astronomie (ref. 6), ii, 953, para 2034.

See Prest Wilfred (ed.), The professions in early modern England (Beckenham, 1987), 54–56, 146–7 and 164. An estate steward's annual pay might average £40–£50; £100 was exceptionally high, although this figure in the early eighteenth century was about the average annual income of clergymen.

Cook Alan , Edmond Halley: Charting the heavens and the seas (Oxford, 1998), 324.

Stewart Ian G. , “‘Professor’ John Flamsteed” in Willmoth Francis (ed.), Flamsteed's stars: New perspectives on the life and work of the first Astronomer Royal (1646–1719) (Woodbridge, 1997), 153.

Baily Francis , An account of the Revd John Flamsteed… compiled from his own manuscripts, and other authentic documents, never before published… (London, 1835; repr. 1966), 37.

Bernouilli Jean , Lettres astronomiques où l'on donne une idée de l'état actuel de l'astronomiepratique dans plusieurs villes d'Europe (Berlin, 1771), 126, 129.

Lalande , Astronomie (ref. 6), i, p. xlix.

Lalande , Astronomie, 3rd edn (Paris, 1792). The list from this edition has been translated by Howse Derek , “Prices of Lalande's astronomical instruments in 1791”, Bulletin of the Scientific Instrument Society, xxi (1989), 9–10.

Darquier Antoine , Observations astronomiques faites à Toulouse… (Avignon, 1777), p. ii.

The map was intended to accompany Vic and Vaissette's Histoire générale de la Province and was the more desired since the absence of any reliable map of the Languedoc was recognised. It was begun by Guillaume de l'lsle in 1724, but was not completed until several years after his death in 1726. In all, three portable quadrants were employed in this operation. For a brief account see Jean-Michel Faidit, L'Observatoire de la Babote, des origines à nos jours (Montpellier, 1986), 23–24.

Information from Jean-Michel Faidit incorporated in the Inventaire National de la Patrimoine Astronomique de France. For the context in Montpellier see Faidit, op. cit. (ref. 19), passim.

Darquier, op. cit. (ref. 18), p. viii, who there states that the instrument was made by Bernier. For the instrument shown in Figure 2, which is in a private collection, see Collection Nachet: Instruments scientifiques et livres anciens. Notice sur l'invention du microscope et son évolution par Albert Nachet… (Paris, re-edition, 1976), 44, no. 134, and Plate XII. Briefly visible when offered for sale at Sotheby's in 1999, the instrument is described in more detail in the sale catalogue of 27 April 1999, Fine instruments of science and technology, lot 106.

de Lalande Jerôme , Bibliographie astronomique avec l'Histoire de l'astronomie depuis 1781 jusquu'à 1802 (Paris, 1803; re-edition, Amsterdam, 1970), 836.

Moinet L. , Nouveau traité général, astronomique et civil d'horlogerie théorique et pratique… (2 vols, Paris, 1848), 532–3, note.

For a brief comparison of English and French portable instruments see Bennett J. A. , The divided circle: A history of instruments for astronomy, navigation and surveying (London, 1987), 119–23.

On which see Cook , Edmond Halley (ref. 12); Thrower Norman J. W. (ed.), The three voyages of Edmond Halley in the Paramour 1698–1701 (Hakluyt Society, 2nd ser., no. 156; London, 1981).

It was presumaby for use at St Andrews that James Gregory sent a specification for a 3ft radius wood quadrant with a brass limb mounted on a ball and socket joint “or something else” to John Collins on 15 February 1669. Rigaud S. J. , Correspondence of scientific men of the seventeenth century (2 vols, Oxford, 1841; repr. Hildersheim, 1965), ii, 186.

For example, the instrument supplied by Bird to St John's College, Cambridge, illustrated in Bennett, The divided circle (ref. 24), Plate 96; or the 40-inch radius instrument at Greenwich (Howse, op. cit. (ref. 1), 114) or the slightly larger instrument (radius 42 inches) supplied by Bird to the new observatory in Stockholm in 1758. Sinnerstad Ulf , “Astronomy and the first observatory”, in Frängsmyr Tore (ed.), Science in Sweden: The Royal Swedish Academy of Sciences 1739–1989 (Canton, MA, 1989), 45–71, pp. 54–55. It is illustrated in Elmqvist Inga and Floren Johan (eds), Tid, Langd & Vikt (Observatoriemuseets Skriftserie, no. 1; Stockholm, 1999), 6.

This list, which makes no claim to completeness, is based on Derek Howse, “The Greenwich List of Observatories: … 1670–1850”, Journal for the history of astronomy, xvii/1 (1986), augmented from diverse sources and in particular surviving instruments recorded in the Inventaire Nationale de la Patrimoine Astronomique de France. In the sources used radii are given in different ways and in different units. They are all here expressed in feet, these being for English instruments the standard English foot, for French instruments the slightly larger (12.67ins) ancien régime pied.

Picard Jean , Mesure de la Terre (Paris, 1671), 5–7. Cf. the comments on this by Levy Jacques , “Picard créateur de l'astrométrie moderne”, in Picolet Guy (ed.), Jean Picard et les débuts de l'astronomie de précision au XVIIe siècle (Paris, 1987), 133–41.

Daumas Maurice , Les instrument scientifiques au XVIIe et XVIIIe siècles (Paris, 1953), 101.

Académie des Sciences Archives: Dossier Godin. See Appendix.

The specification for this instrument is printed in Daumas, op. cit. (ref. 29), 85–86, from Observatoire de Paris Archives: Correpondence de Lisle, I, 1.

Particularly from Le Monnier, see Bennett, op. cit. (ref. 4), 5ff.

Nothing is known of this maker apart from what Godin tells us in the present memoir.

A member of the Founders' Corporation of which he was a Juré 1701–3, Jean Chapotot was active at the Quay de l'Horloge du Palais “à la Sphère”, Paris, from at least 1676 from which year an instrument signed by him has survived. The optical parts of his portable astronomical quadrants were made in the 1720s by Le Bas his.

The specification for this is printed from Observatoire de Paris Archives: Correspondance de l'Isle, I, 1, by Daumas, op. cit. (ref. 30), 85–86.

Charles Antoine de la Roche Aymon (1692–1770), Bishop of Tarbes from 1729 to 1740.

Petr Osipovich Golynin (1719–46) was trained first in the Navy Ministry, then in the instrument workshops of the Academy of Sciences in St Petersburg making sun-dials and other instruments. See Chenakal Valentin L. , transl. by Ryan W. F. , Watchmakers and clockmakers in Russia 1400–1850 (Antiquarian Horological Society Monograph no. 6; [London], 1972), 23.

These two letters are unclear but are probably to be read as f[il]s. This is Pierre-Claude Lebas, the son of Jean Lebas, in whose right he succeeded to a “logement” in the Louvre for which the certificate is dated 8 September 1720. A second certificate which associates his mother with him is dated 10 April 1725. It was probably he who fitted a portable astronomical quadrant owned by the astronomer Eisenschmid in Strasbourg with a telescope in which the reticule was replaced by a glass disc with a fine line engraved on it, as La Hire had suggested.