Magnetic map of the Earth, 1734.
© Science Museum / Science & Society Picture Library
The caption on the map reads, in translation: 'Map of the whole Earth showing Magnetic declination, arranged for the year 1700 by Edmund Halley together with inclinations observed by Pound'. California is shown as a separate island. Illustration from 'Principia rerum naturalium' (The principia, or, The first principles of natural things) by Emanuel Swedenborg (1688-1772) published in Dresden in 1734.