Gauss’ and Weber’s “Atlas of Geomagnetism” (1840) Was not the first: the History of the Geomagnetic Atlases

In the beginning there were geomagnetic charts which were interesting mainly for seafaring nations. The first geomagnetic atlas was printed in London in 1776; its author was the mathematician, cartographer, and astronomer Samuel Dunn, whose aim had been to ameliorate the navigation especially to support the trading of England with the East Indies. The American John Churchman, however, was mainly surveyor; his magnetic atlas was published in four editions, in 1790, 1794, 1800, and 1804. Churchman was in contact with George Washington and with Thomas Jefferson, as far as his geomagnetic charts were concerned; he also became a member of the Academy of Sciences in St. Petersburg. Churchman was convinced that the magnetic pole in the north could be found in northern Canada. The Norwegian astronomer and physicist Christopher Hansteen was convinced that there were two magnetic poles in the north and two in the south; his atlas was published in 1819. One of the magnetic poles in the north should be in Siberia. Hansteen found support by the king of Sweden and Norway so that he undertook an expedition to Siberia (1828–1830). Carl Friedrich Gauss and Wilhelm Weber began to study geomagnetism in 1831: They believed that there were only two magnetic poles, one in the north and one in the south. They were able to calculate their positions by means of Gauss’ new theory of geomagnetism (1839); as sailors found out, their coordinates turned out to be nearly correct. Gauss’ and Weber’s Atlas is without doubt the most famous; it was published in Leipzig in 1840, including 18 geomagnetic charts. On two of these charts, equipotential lines were presented for the first time in history.