This is a MapHist list message. News: If you don't get messages anymore, go to http://www.maphist.nl for news about the new MapHist Forum o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o +
I recently was asked a question about a compass or wind rose that had some odd numbers marking the 32 points. Instead of degrees or points it's marked 17 1/2 over the fleur de lis at north and then in both directions, every 11.25 degrees the markings go 18 19 21 25 31 1/2 46 88 0 at due west and due east. The actual angles are 11.25 degrees per division, but if you plot these numbers against the actual angles you get a very smooth curve that looks exponential or maybe logarithmic. This graphic was seen in the Ch. Columbus museum on Porto Santo, a small island of Madeira, Portugal. The question is, what do these numbers mean? I've got a couple of images, but they're too big to show you here. I thought I'd just ask if anyone knows anything about this sort of numbering before I go to further lengths. For all I know this could be an easy one. I just can't figure out if this is some sort trigonometry calculator or what it was supposed to do for the mariner of Columbus' time. (I don't have a date for it either; I'm assuming it's 15th century.) So is this a common numbering scheme or do you need to see the pictures? Regards, Bill Thoen GISnet http://gisnet.com 303-786-9961
_______________________________________________ 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
