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Pedro Nunes' Discovery of the Loxodromic Curve (1537). How Portuguese Sailors in the Early Sixteenth Century, Navigating with Globes, had Failed to Solve the Difficulties Encountered with the Plane Chart

Published online by Cambridge University Press:  23 November 2009

W. G. L. Randles
W. G. L. Randles
Affiliation:
(Maison des Pays lbériques, Université de Bordeaux III)
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Extract

In the early sixteenth century, Portuguese navigators on voyages outside the tropics ran into an unexpected problem in navigating with the plane chart since the latter took no account of the convergence of the meridians. Voyages between Brazil and the Cape of Good Hope were accomplished much faster than the chart led them to forsee. To overcome this problem, were Portuguese pilots of the first half of the sixteenth century using globes to set their courses with on great circle courses? The general opinion is that they were not. Yet the mathematician Pedro Nunes (1502–78) describes in a short treatise entitled Tratado que ho Doutor Pedro Nunez fez sobre certas duvidas na navigação (published in 1537, but probably written in 1534) how the navigator Martim Afonso de Sousa, on his return from the east coast of Brazil in 1530–2, had asked him to solve several problems of navigation encountered on the voyage.

Keywords

1. History.Loxodromes.3. Rhumb lines.
Type
Research Article
Information
The Journal of Navigation , Volume 50 , Issue 1 , January 1997 , pp. 85 - 96
Copyright
Copyright © The Royal Institute of Navigation 1997

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References

NOTES AND REFERENCES

1 Cf. Randies, W. G. L., ‘From the Mediterranean portulan chart to the marine world chart of the Great Discoveries: the crisis in cartography in the sixteenth century’, in Imago Mundi, vol. 40 (1988), pp. 111–114.Google Scholar
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6 Rodolfo Guimaräes, Sur la vie et l'œuvre de Pedro Nunes, Coimbra, 1915, p. 26 (original in French). In a letter dated 8 April 1985, Professor Luis de Albuquerque wrote to us that it was obvious to him that Martim Afonso de Sousa could not have been using a contemporary chart and that it was probable that he was carrying a globe in spite of their use being prohibited by the King.Google Scholar
7Coelho, J. Ramos (ed.), Alguns Documentos da Torre de Tombo, Lisbon, 1892, pp. 138–139. (‘… defendemos que nao facam nenhuns mestres das cartas de marear, nem outros alguns oficiais nenhumas pomas grandes nem pequenas, de pouco, nem muito, porque nao queremos que se facam em maneira alguma …’)Google Scholar
8 The term ‘quadratic chart’ is used by Nunes, Pedro, Tratado… em defensam da carta de marear, Lisbon, 1537, in Idem, Obras, vol. 1, pp. 176–177. Cf. Luís de Albuquerque's very pertinent remarks that Portuguese nautical charts of the sixteenth century were not in fact true quadratic charts. Luís de Albuquerque, Ciência e experiência nos Descobrimentos Portugueses, Biblioteca Breve, Lisbon, 1983, pp. 15–19, and Idem. ‘Considerações sobre a carta portulano’, in Revista da Universidade de Coimbra, vol. 31 (1984), pp. 19–22.Google Scholar
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15 In his Portuguese text, Nunes believed that the pole would be reached, but in his Latin text of 1566, he wrote that the ship would get closer and closer, but never touch it. Pedro Nunes, ‘Tratado…em defensam da carta de marear’ in Obras, vol. I, p. 184, and Pedro Nunes, Opera, Basel, 1566, p. 173.Google Scholar
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24 The late Professor Pierre Costabel emphasized to us the importance of the sequential nature of the two movements.Google Scholar
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