The Selenographia of William Gilbert: His Pre-Telescopic Map of the Moon and His Discovery of Lunar Libration

The sole extant manuscript map forms ff. 75–6 of Gilbert William , “De mundo nostro sublunari”, British Library Royal Ms. 12 F. XI. The redrawn map is in Whitaker Ewen , Mapping and naming the Moon: A history of lunar cartography and nomenclature (Cambridge, 1999), 13. It is reproduced here by permission as Figure 2; see also Whitaker Ewen , “Selenography in the seventeenth century”, in Taton R. Wilson C. (eds), The general history of astronomy, ii: Planetary astronomy from the Renaissance to the rise of astrophysics. Part A: Tycho Brahe to Newton (Cambridge, 1989), 119–43, p. 121.

I am indebted to an anonymous referee who required a defence of the label, because if he were to “compare Gilbert with what Leonardo drew, a century earlier…, Gilbert's ‘map’ is a very poor representation indeed”. Leonardo's work can be seen in Reaves Gibson Pedretti Carlo , “Leonardo da Vinci's drawings of the surface features of the Moon”, Journal for the history of astronomy, xviii (1987), 55–8. This article supports Whitaker's view that da Vinci's made “crude sketches” but Gilbert “may perhaps be thought of as the first selenographer”. See Whitaker , “Selenography” (ref. 1), 118. As the referee noted, the answer depends upon what one means by a map, and I address the issue briefly below.

For evidence that Harriot saw the map see Pumfrey Stephen , “Harriot's maps of the Moon: New interpretations”, Notes and records of the Royal Society, lxiii (2009), 163–8. For Bacon see Spedding James Ellis Robert Leslie Heath Douglas Denon , The collected works of Francis Bacon (15 vols, London, 1857–74), iv, Novum organum, Part II, aph. XXXIX, 308; Bacon's first manuscript use, and specific mention of Gilbert, occurs in Bacon , Works, v, “Descriptio globi intellectualis”, 760: “et selenographia illa sive typus lunae, quem animam agitabat Gilbertus iam ex Galilaei et aliorum industria praesto esse videatur.” It has been claimed that Galileo picked up his neologism from Bacon. See Migliorini Bruno Ghinassi Ghino , Storia della lingua italiana (Bompiani, 1994), 443.

Gilbert William , De mundo nostro sublunari: Nova physiologia contra Aristotelem (Amsterdam, 1651); for Hevelius see Vertesi Janet , “Picturing the Moon: Hevelius's and Riccioli's visual debate”, Studies in the history and philosophy of science, xxxviii (2007), 2007–21.

For the two programmes see Whitaker , Mapping (ref. 1), chaps. 1–3.

Kelly Sister Susanne , The De mundo of William Gilbert (Amsterdam, 1965). Two sites that reproduce the image are Charles Wood, “Timeline of lunar exploration”, Chuck Wood's Moon: Compendium of lunar science and history, url: http://www.lpod.org/cwm/Timeline/1600s/1603-Gilbert.html, last accessed 11 August 2010, and (in higher resolution) “Early lunar map”, European Space Agency: Science and Technology, url: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=21885, last accessed 13 August 2010.

Montgomery Scott L. , The Moon and the Western imagination (Tucson, 1999), 99, 220. Montgomery added that Gilbert “did something utterly remarkable: He named [the spots], even portions of them, all after earthly geographic forms” such as seas, continents and even “Britannia”. As a result, he suggested, the map encoded colonialist aims. Without denying that, I argue that the aims were primarily astronomical. On pp. 103–4 Montgomery also discusses the name “Cape Bicke”, concerning which see the appendix to this article.

Whitaker , Mapping (ref. 1), 13, 15. He wrote that “Gilbert used an 8 × 8 grid square to better position the features”, but we should remember that the surviving manuscript is a copy prepared after Gilbert's death and the grid could have been a device introduced by the copyist. The correlations are sometimes loose, and one has some sympathy with the lunar astronomer, Charles Wood, who has written that “Gilbert's drawing is about the minimum a careful observer would notice! The locations and sizes of the maria are poor, and no craters — Not even Tycho — Are shown. This drawing is famous for being the only pre-telescopic drawing, but it is not a careful rendition of what is visible”. See Wood , “Timeline of lunar observation” (ref. 6).

J. H. Chalmers notes that more than 300 definitions in English have been collected for the period 1649–1996. See Chalmers , “What was a map? The lexicographers reply”, Cartographica, xxxiii (1996), 1–12. For the list itself see Andrews J. H. , “Definitions of the word ‘map’, 1649–1996”, MapHist discussion papers, url: http://www.maphist.nl/discpapers.html, last accessed 17 May 2010.

Thrower Norman J. W. , Maps and civilization: Cartography in culture and society (Chicago, 1996), 254. The ICA definition is reproduced as no. 187 in Andrews's list above (ref. 9).

One sea, two bays, two headlands, a promontory and nine landmasses (six of them labelled).

Gilbert , “De mundo” (ref. 1), I.4, f. 7: “Quere plura in tractatu de luna”; cf. Gilbert , De mundo (ref. 4), 9. The treatise seems to form Book II, chaps. 13–19.

Gilbert , “De mundo” (ref. 1), f. 74v. Translations are by me and Ian G. Stewart, my co-editor of a forthcoming edition and translation of the manuscript “De mundo”. We transcribe the Latin thus: “Selenographiam sive Lunae descriptionem damus, quam male antiquitas omnis praetermisit: Qua post tot annorum curriculum intelligeremus, num in illa maculae apparentes immutatae fuissent praeterea talis descriptio necessario requiritur, in observatione corporis lunaris ut intelligatur num omnino non volvatur, ut ab Aristotele persuasum est et acceptum, aut reliqua ex parte convertat se, Tum quomodo in motu suo menstruo inclinat polis eius polis scilicet corporis, versus mundi partes aliquas certas; Tum etiam qua ratione telluri coniuncta sit, et cum telluris positione consentiat; Quae omnia recte observari, aut aliquo modo cognosci non possunt sine partium ipsius Lunae per maculas illas distinctione. Quod vero Lunam tellurem alteram, minorem, aut corpus aliud telluris modo ordinatum existimamus, id postea confirmabimus, Damus iam apparentis orbis graphiam tanquam geographiam alteram, quibusdam nominibus geographicis discretam, ut melius quisquam et facilius, illam mente compraehendere possit firmiusque retinere.” See Gilbert, “De mundo” (ref. 1), f. 74r. In the 1651 printed edition (ref. 4), the reasons appear in almost identical words on p. 172. The map is inserted between p. 172 and p. 173.

This purpose alone was reported in 1969 by Kopal but he seems to have been ignorant of the three more remarkable purposes. See Kopal Ždenek , “The earliest maps of the Moon”, The Moon, i (1969), 59–66, p. 61.

Gilbert , “De mundo” (ref. 1), f. 78r. “Si enim supra lunam oculus foret, anne discerneret mutationem telluris in vegetabilibus, aliisque generationibus et corruptionibus?” Pace Kopal (op. cit. (ref. 14), 61), it would not have “consoled Gilbert if he knew that no such changes have been noted since the advent of the telescope”.

Gilbert , “De mundo” (ref. 1), f. 74r.

Pumfrey Stephen , “The astronomer's role and the natural philosopher's role in the sixteenth century reconsidered: The case of William Gilbert”, paper presented at the Annual Conference of the British Society for the History of Science, Aberdeen, 23 July 2010.

Aristotle , The works of Aristotle, ed. by Ross W. D. , transl. by Stocks J. L. (12 vols, Oxford, 1930), ii, De Caelo, Book II, chap. 8, 290a8–290a29.

See Galilei Galileo , Dialogue concerning the two chief world systems, transl. by Drake Stillman (Los Angeles, 1962), 66, 67. Galileo was driven by his conservative celestial mechanics to assert incorrectly that all libration was topocentric, so that “anyone looking from the centre of the Earth would always see the same lunar disc bounded by exactly the same circumference”. Gilbert considered the geometry of topocentric libration in “De mundo” (ref. 1), Book II, chap. 19, f. 83v, and thought that it was too small to account for the observed libration.

See, for example, Cherrington Ernest H. Jr , Exploring the Moon through binoculars and small telescopes (New York, 1984), 36. “The effect of the libration in longitude may be observed by simply noting the position of Mare Crisium with respect to the eastern limb from night to night” and the “libration in latitude may be checked by observing the changing position of the long narrow Mare Frigoris with respect to the northern limb”.

I.e. Long Island, North Island and Britain. The manuscript has the label “Brittannia” which is corrected to Britannia in the printed edition.

See Pumfrey Stephen , “Magnetic philosophy and astronomy”, in Taton Wilson (eds), op. cit. (ref. 1), 45–53.

Gilbert , “De mundo” (ref. 1), f. 82v. “Observatio plenilunii in capricorno, quod maior sit distantia meridionalis maculae lunae, ab extremitate orbis luminis quam in Cancro, quod esset contrarium, si non esset inclinatio polorum lunae versus polum deferentis sui, sive polum Zodiaci, quia plus videmus in inferiore parte lunae”.

Gilbert , “De mundo” (ref. 1).

Whitaker , Mapping (ref. 1), 13. He assumed that it was Gilbert who had “mislocated some outlines one square too far north before realizing his error”.

See ref. 4, and Gruter , “Ad Lectorem” in Gilbert, De mundo (ref. 4).

See Montgomery , op. cit. (ref. 7), 103–4.