Next message: George Huxtable: "Re: Historical Magnetic Variation/Declination"
I had some time today to put together a few different ways of viewing the
historical magnetic declination/variation maps from the USGS. There's a large
animated GIF as well as a frame-by-frame viewer available on my web site here:
http://HistoricalAtlas.com/mag
Looking at those isolines, it's interesting to consider how nearly magnetic
variation came to being a reasonable method for determining longitude. As
Halley discovered in th early 18th centurt, if only the lines were as "well
behaved" in the rest of the oceans as they were in the South Atlantic in that period,
it just might have been workable. Who knows... longitude might have been
found with a magnetic compass instead of a sextant or chronometer.
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
