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I think it is an illustration of the 16th century "rule to raise a degree", i.e. a means of calculation of a ship's position based on the assumption that there are 17 1/2 leagues to a degree: If you sail north or south you have to sail 17 1/2 leagues to arrive one degree to the north or south. And so on for every point of the compass (11,25 degrees). And there can only be 8 numbers, because if you sail east or west your latitude doesn' t change at all. Diagrams of this sort can be found in manuals of navigation of the 16th and 17th century. Dr. Wolfgang Köberer Wolfsgangstr. 92 D-60322 Frankfurt am Main Tel: + 49 69 95520851 Fax: + 49 69 558400 e-mail: koebe...@navigationsgeschichte.de _______________________________________________ MapHist: E-mail discussion group on the history of cartography hosted by the Faculty of Geosciences, University of Utrecht. The statements and opinions expressed in this message are those of the author and do not necessarily reflect those of the University of Utrecht. The University of Utrecht does not take any responsibility for the views of the author. List Information: http://www.maphist.nl Maphist mailing list Maphist@geo.uu.nl http://mailman.geo.uu.nl/mailman/listinfo/maphist
