Lisboa, João De

(b. Portugal;d. Indian Ocean, before 1526),

navigation.

It has been claimed that Lisboa, a Portuguese pilot, accompanied Vasco da Gama on the voyage on which the route to the Indies was discovered (1497-1499), While this claim is probably false, there are documents proving that he navigated the coast of Brazil (at an unknown date), that he participated in an expedition to the fortress of Azamor in northern Africa (1513), and that he sailed to the Indies at least three times: in 1506, as pilot of the fleet led by Tristão da Cunha; in 1518, in the squadron of Diogo Lopes de Sequeira; and in the squadron commanded by Filipe de Castro in 1525. The last fleet had a difficult crossing from Madagascar to the Curia-Muria Isles; and it is likely that Lisboa, then advanced in age, did not survive this arduous passage.

In the course of his first documented visit to the Indies, Lisboa and the pilot Pêro Anes carried out observations to determine the magnetic declination with the aid of the constellations Ursa Minor and the Southern Cross, The method is set forth in the Tratado da agulha de marear, a small book written by Lisboa in 1514. It contains the first description of the nautical “dip” compass and the first presentation of a method for measuring the magnetic declination. Present knowledge of the text derives from copies that are incomplete and faulty but numerous enough to allow one, through comparison, to determine its complete and correct form. The treatise consists of an introduction and the chapters. The first three are concerned with the construction of the compass, the following three with the observation of the magnetic declination with the aid of stars, and the seventh with the method of magnetizing the needle. In the last three chapters Lisboa presents a theory without any experimental support; he assumes that the declination of the compass undergoes variations proportional to the longitude and is convinced that this “law” can enable sailors to determine this coordinate.

BIBLIOGRAPHY

Portions of João de Lisboa’s treatise can be found in the following MSS:

“Livro de marinharia,” attributed to Lisboa himself (but completed about 1550, well after his death), in the National Library, Lisbon. The text was published by Brito Rebelo (Lisbon, 1903).

“Livro de marinharia” by Bernardo Fernandes, in the Vatican Library, Codex Borg. lat. 153. An ed. was published by Fontoura da Costa (Lisbon, 1940).

“Livro de marinharia” by André Pires in the Bibliothèque Nationale, Paris, MS portugais, 40, Published by L. de Albuquerque (Coimbra, 1963).

“Livro de marinharia” by Gaspar Moreira, in the Bibliothèque Nationale, Paris, still unpublished.

“Rotero de navigación,” written in Portuguese despite the title, in the library of the Academia Real de la Historia, Madrid, Cortes 30-2165. This compilation is anonymous and is unpublished.

LuÍs de Albuquerque