FRANCIS MADDISON MEDIEVAL SCIENTIFIC INSTRUMENTS AND THE DEVELOPMENT OF NAVIGATIONAL INSTRUMENTS IN THE XVfh AND XVIth CENTURIES COIMBRA-1969 FRANCIS MADDISON IMPRENSA NACIONAL MEDIEVAL SCIENTIFIC INSTRUMENTS AND THE DEVELOPMENT OF NAVIGATIONAL INSTRUMENTS IN THE XVfh AND XVIth CENTURIES COIMBRA-1969 Separata da Revista da Universidade de Coimbra Vol. XXIV MEDIEVAL SCIENTIFIC INSTRUMENTS AND THE DEVELOPMENT OF NAVIGATIONAL INSTRUMENTS IN THE XVth AND XVIth CENTURIES by FRANCIS MADDISON 'The history of scientific instruments .. is one of the best approaches to the understanding of scientific progress, but it is full of difficulties; each instrument is developed gradually; none is created in one time for all time by a single man.' GEORGE SARTON 'CUm vero artis navigatoriae peritia... Mathematicarum scientiarum admini­ culis adhibitis suum apud nos splendorem posse consequi facile perspiceres, Thomas Hariotum iuvenem in illis disciplinis excellentem, honestissimo salario iam diu donatum apud te aluisti, cuius subsidio horis successivis nobilissimas scientias illas addisceres, :usque familiaries duces maritimi, quos habes non paucos, cum praxi theoriam non sine fructu incredibili coniungerent .. Unam hoc scio, unam & unicam rationem te inire, qua primo Lusitani, deinde Castellani, quod antea toties cum non exigua iactura sunt conati, tandem ex animorum votis perfecerent'. RICHARD HAKLUYT to SIR WALTER RALEGH, 1587 (1). [Note. This brief survey, as originally read at the I. Reuniiio lnternacional de His­ t6ria da Nautica, was cast in the form of a commentary on lantern slides. In preparing the paper for the press, it has been substantially rewritten and the author has taken the opportunity not only to supply bibliographical references to more detailed treatments of specific topics, but also to refer to other papers which were read at the Reuniiio.] (1) The first quotation is from the essay, 'Ptolemy in his Time', in GEORGE SARTON, Ancient Science and Modern Civilisation, Lincoln (Nebraska), 1954, p. 44. The second quotation is from the dedica~ion of RICHARD HAKLUYT's, De Orbe novo Petri Martyris ... Decades octo, Paris, 1587, printed in E. G. R. Taylor (ed.), The Original Writings & Correspondence of the Two Richard Hakluyts (Hakluyt Society, second series, vol. LXXVII), London 1935, vol. II, p. 360. (Here, and elsewhere in this paper, I have expanded the contraction signs in printed works, putting the added letters in italics). A translation of this passage, by F. C. Francis, is given by TAYLOR, op. cit., pp. 366-367, and in DAVID W. WATERS, The Art of Navigation in England in Elizabethan and Early Stuart Times, London, 1958, appendix n. 0 16, p. 546. On Harriot, see n. 155, below. 4 INTRODUCTION rn his chronicle of the reign of D. Manuel, Damiao de Go is wrote : 'Neste tempo dom Emanuel nam era casado, nem tinha tornado diuisa, segundo costume dos Prin((ipes, pelo que El REI dom Ioao !he deu per diuisa ha figura da Sphera, perque hos Mathematicos representam ha forma de ha machina do ((eo, & terra, com todo los outros elementos, cousa despantar, & que pare((e que nao care­ ((eo de mysterio prophetico, porque assi quomo estaua ordenado per DEOS que elle houuesse de ser herdeiro del Rei dom Ioao, assi quis que ho mesmo Rei a quem hauia de suc((eder, lhe desse hum a tal diuisa ... ' (2). This device of an armillary sphere, albeit somewhat distorted by artistic licence, may be seen on a gold coin (known as a meia esfera) minted for Por­ tuguese India during the reign of D. Manuel, and is familiar as a motif of Manueline architecture in Coimbra and Lisbon (3). The device is appropriate, for in the last years of the reign of D. Joao II (ace. 1481) and in the reign of D . Manuel (ace. 1495) navigation developed from what was primarily pure seamanship into a practice which, as Fontenelle put it, 'hath a necessary connection with Astronomy' (4), and which was to rely increasingly on the use of a number of specially devised sci entific instruments. These were instruments which not only could be used satisfactorily on board ship, but which were practical and robust enough for use by seamen and which could be made available in quantity and economically. The history of navigational instruments must specially take account of that elusive interaction between everyday practice of long tradition, scientific theory, and the available tech­ nology and its economic foundations. The nature of the interaction may often elude the historian, but as always science in history is rarely isolated from it. Our knowledge of the practice of navigation in early medieval Europe . is very imperfect. We may deduce from the words of the Roman poet Lucan (c. A.D. 65, that the Pole Star was favoured as an aid to naviga- (2) DAMIAO DE G61s, Chronica do felicissimo Rei Dom Emanuel, Lisbon, J 566, cap. Y, f. 5v. See LUCIANO PEREIRA DA SILVA , 'A Esfera armilar nas moedas portuguesas', Obras comp/etas, vol. III, pp. 367-371. (3) For details, see PEREIRA DA SILVA, op. cit.. A constant error in these represen­ tations of an armillary sphere is that the ecliptic circle touches the polar circles. (4) Bernard le Bovier de Fontenelle, J 699, quoted from an early English translation (which I have not been able to identify by E. G. R . TAYLOR eM. W. RICHEY, The Geometrical Seaman. A Book of Early Nautical Instruments, London, 1962, p. [ii] . 5 tion (5); we may read in the Northern saga literature of a husanotra, apparently a device used in navigation, but know nothing of its nature or exact function, (6) and speculate about the s6larsteinn owned by St Olaf early in the eleventh century (7); we may suspect the aid derived from observation of the flight of birds, but lack early documentation (8). All we may reasonably (5) MARCUS ANNAEUS LUCANUS, De bello civi/i(Pharsalia), VIII, 11. 165-168 especially: 'Signifero quaecumque fluunt labentia caelo Numquam stante polo miseros fallentia nautas, Sidera non sequimar; sed, qui non mergitur undis Axis inocciduus gemina clarissimus Arcto, Ille regit puppes.' Cf. also op. cit., III, 11.218-219, where speaking of the Phoenicians, Lucan writes: 'Has ad bella rates non flexo limite ponti Certior haud ullis duxit Cynosura carinis.' For a discussion of the first of the passages cited, see E. G. R. TAYLOR, The Haven­ Finding Art. A History of Navigation from Odysseus to Captain Cook, London, 1956, pp. 46-47. (6) Husanotra is variously translated into Latin as gubernaculum, cornis and scopae, and may in no way be a navigational instrument. See the discussion in FARLEY MoreAT, Westviking. The Ancient Norse in Greenland and North America, London, 1966, pp. 354-355. (7) For a brief discussion of the s6/arsteinn (sunstone) and of the supposed Norse 'bearing dial', see GwYN JoNES, A History of the Vikings, London, 1968, pp. 192-194. On both instruments, in addition to the references given by Jones, see THORKILD RAMSKOU, Solstenen. Primitiv navigation i Norden for kompasset, Copenhagen, 1969, who compares the use of the s6/arsteinn (sols ten in Danish) with that of the modem Kollsman Sky Compass ('twilight compass') in which a Polaroid filter is used to analyse polarized light from the zenith when the sun is near the horizon (between + 30° and - 7°). The so/arstei nn, mentioned in Flateyjarbok and other Icelandic sources, is explained as a piece of cordierite (or other naturally occurring crystal) used in such a way that the direction of the sun may be determined by the polarisation of light transmitted by the crystal. In this connection, it is interesting to recall that Sir Charles Wheatstone (1802-1875) invented a Polar Clock or Dial' incor­ porating a Nicol prism; see Wheatstone, 'On a Means of Determining the Apparent Solar Time by the Diurnal Changes of the Plane of Polarisation at the North Pole of the Sky', Report of the Eighteenth Meeting of the British Association for the Advancement of Science - 1848- Swansea, pp. !Off. A Wheatstone polar clock, made by Darker of Lambeth, is preserved in the Museum of the History of Science, Oxford. The ability of the Norsemen to determine their latitude is discussed by JONES, foe. cit .. and by MowAT op. cit., p. 352. The concept of latitude to be considered in connexion with Norse navigation is, of course, that of 'latitude' relative to any reference point in which the variation of observed altitude of the Pole Star (when visible!) is equated with sailing north or south of the home port, but any form of 'latitude' navigation in early medieval times is of considerable interest in relation to the contact between different cultures. See ROLANDO LAGUARDA TRIAS, 'Interpretacion de los vestigios del uso de un metodo de nave­ gaci6n preastron6mica en el Atlantica' in this publication; also MICHEL MoLLAT, 'Solei! et navigation au temps des Decouvertes', Le Solei! a Ia Renaissance. Science et mythes. Colloque international ... avril 1963 ... (Universite libre de Bruxelles. Travaux de l'Institut pour )'Etude de Ia Renaissance et de l'Humanisme II), Brussels & Paris, 1965, pp. 89-106. (8) The whole question of the influence of the observation of natural phenomena upon the history of navigation deserves much further study. Two interesting late references may be cited here: MARTIN MARTIN in A Late Voyage to St. Kilda, the Remotest of all the Hebrides, or Western Isles of Ecotland. With a History of the Island, Natural, Moral, 6 be sure of is that, by the end of the thirteenth century, the seamen in the Mediterranean could have used a chart, a magnetic compass and sailing directions, possibly also a sand-glass. Sailing, of course, was by dead­ reckoning. Directions were given in the sailing directions, according to the traditional wind directions, as winds, half-or quarter-winds, and the distance sailed was measured merely by estimating the ship's speed and measuring; and in the thirteenth century rudimentary trigonometric tables were applied to navigation.