A Discourse Mathematical on the Variation of the Magneticall Needle. Together with its admirable Diminution lately discovered.
London: William Jones, 1635. First edition, extremely rare, of Gellibrand’s most important discovery: the secular change in magnetic declination, or variation. According to William Gilbert in his De Magnete (1600), the existence of magnetic declination, the difference in direction between geographical and magnetic north, is a result of the magnetic..... More
Item #5121