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    Re: Portuguese shipwreck question
    From: Wolfgang Köberer
    Date: 2009 Nov 4, 21:46 +0100

    Now that all the pleasantries have been exchanged, I may return to the original questions in this thread:


    John Huth asked:


    "1.) What evidence is there for Portuguese vessels sailing on a far west path around West Africa - getting close to what is now Brazil?


    2.) Any idea what modern town Sigdemessah might be?   Timbuktu?" 


    Ad 1: The passage back from Guinea (and later from India/the Moluccas) „on a far west path around West Africa” had been established by the Portuguese in the second half of the 15. century. It was called the “Volta da Mina” (from Guinea) or the “Volta do mar largo” (from farther down south). It was necessitated, indeed, by the trades: the Portuguese sailors could not hug the African coast going north so turned norhwest and later east. This practise was facilitated by the development of the “Caravel” with lateen rig.

    This practice was - by the way - also the incentive to develop celestial navigation, as traditional methods of navigation obviously could not be of any help out on the ocean. This method and the development of celestial navigation has been studied in depth by Portuguese historians of navigation since the beginning of the last century; among others Bensaude, Coutinho, Cortesao, Albuquerque etc. A basic text - in English - is in Vol. II of Cortesao’s “History of Portuguese Cartography” (Coimbra 1971). This text (“Astronomical navigation” and “Instruments of Navigation”) by Luis de Albuquerque has also been published separately. And there are still Portuguese scholars publishing relevant contributions today, among them Estacio Dos Reis and Captain Malhao Pereira whom some list members have met a couple of years ago at the Instrument Symposium at Greenwich.


    Ad 2: This is a very difficult question: What you are trying to do is to identify an ancient name with a modern location and then assess the accuracy of the ancient positional data. There are several problems - all very well explored in the study of portolan charts - the most difficult being the identification of the ancient place. This has been illustrated quite well by Peter and George trying to create plausibilities by arguments from a completely different field: French history. Now I am not versed in French history and its intricacies at all; I just noted that the latitudes in the tables you gave do not fit the place they discussedl. They agree roughly with Lyon (and not with Laon). That makes me wonder because - of course - latitudes could be measured very easily even at that time and should not be out by many degrees. As far as longitudes are concerned they depend, of course, on the meridian of zero longitude that the author of the tables choses - and that might be another difficulty.


    So trying to fit the positional data of ancient tables with modern data is interesting - I’ve tried it myself in analysing the tables of the oldest German manual of navigation - but sometimes you are left just guessing.




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