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Edmund Halley

Edmund Halley

Halley is one of the great scientists of any nation, famed as an astronomer and geographer of enormous influence, most importantly on the theories of Isaac Newton. Halley was also a celebrated mapmaker, bringing his scientific training to bear in producing a new generation of maps incorporating the newest scientific data. His father, also Edmund, was a prosperous London soap maker, who was murdered in 1684, leaving his son with the money to pursue his interests.

In 1676 Halley sailed to St. Helena, off the west coast of Africa, to study the stars in the southern hemisphere. The resultant star catalogue was dedicated to Charles II, as was the accompanying planispheric chart of the stars. He also included a historical description of existing stellar catalogues, citing the works of Brahe, Flamsteed, Hevelius and Cassini, and also contributed an account of his own voyage to St. Helena.

On his return he was elected to the Royal Society, and he served the Society in a number of capacities over the years. He was Clerk to the secretaries of the Royal Society, Sir Thomas Hoskins and Thomas Gale from 1685 to 1699, and editor of the ‘Philosophical Transactions’ from 1685 to 1692. In 1720 he was appointed Astronomer Royal in succession to John Flamsteed.

From 1698 to 1700 Halley navigated the Atlantic as captain of the ship Paramore, to measure magnetic variation, hoping that this might be a means to accurately determine longitude at sea, an age-old problem for mariners. Although this theory was unsuccessful, the observations served as material for his important charts of the Atlantic Ocean (‘A New and correct Chart shewing the Variations of the Compass in the Western & Southern Oceans as observed in ye year 1700’), published in 1701, and his 1704 chart of the world. These were the first printed charts to depict lines of equal magnetic variation in the oceans (isogonic lines, or ‘Halleyan lines’ as they were originally termed). His contemporaries, and successive generations, quickly adopted these lines for their world charts,.

In 1702 Mount and Page published ‘A New and Correct Chart of the Channel between England & France with considerable improvements’, notable for the inclusion of Halley’s measurements for the tides and currents of the Channel, again rapidly adopted by later mapmakers. 

From 1715 onwards, working with John Senex, semi-official mapmaker of the Royal Society, he published a series of eclipse maps: ‘A Description of the Passage of the Shadow of the Moon, over England, in the Total Eclipse of the Sun, on the 22d. day of April 1715 in the Morning’, with a later state updated to show the actual passage of the eclipse; a second map of the April 1715 eclipse titled ‘A Description of the Passage of the Shadow of the Moon over England as it was observed in the late Total Eclipse of the Sun April 22.d 1715 Manè’; and a predictive map for the 1724 eclipse titled ‘A Description of the Passage of the Shadow of the Moon over Europe, as it may be expected, May 1724 in the Evening’.

While there are numerous earlier predictive maps of eclipses, Halley’s is the first scientifically based, accurate predictive map of an eclipse, forecasting the passage of the eclipse over England and southern Scotland, accurate to about four minutes. Halley’s reputation was greatly enhanced when he correctly predicted the return of the comet that now bears his name.

In 1728, with Nathaniel Cutler, Halley contributed the text, ‘A General Coasting Pilot’ to the ‘Atlas Maritimus et Commercialis; Or A General View Of The World’ published by James Knapton and John Knapton, and a consortium of leading London publishers, illustrated with charts drawn by John Harris, John Senex and Henry Wilson.

Halley's status was such that his name was frequently used as a puff for publications that he was not connected with, while he was also a popular dedicatee for contemporary maps, but he was also called upon to testify to the worth of maps, notably Henry Popple’s ‘A Map of the British Empire in America with the French and Spanish Settlements’.