Next message: Frank Reed: "Re: Navigation News article on leap seconds."
"Jonkers has taken magnetic information from many European logbooks and
sailing directions between 1500 and 1800. One of his observations is that
there's a scatter in measurements of magnetic variation, with a standard
deviation of about 2.5 degrees."
A problem with this sort of analysis, of course, is that it's dependent on
knowing the vessel's actual position. Before 1800, that's usually only
possible at known landfalls.
And for those who haven't seen it:
http://www.HstoricalAtlas.com/mag/
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
