The science of early cartography focussed more on its geographical content and its projection than anything else. But it was the flowering of the scientific renaissance under King Charles II of England that really brought about many new studies. The formation of the Royal Society in 1660, given a royal charter two years later, was a major stimulus to the field. Amongst its greatest members of the time were Robert Boyle and Sir Isaac Newton. It was Edmond Halley who expanded in to the field of thematic mapping. This is when a map reflects specific data rather than a general map which displays all sorts of material. The modern day equivalent would be the distribution of population or rainfall for example. There are earlier works such as those of Ortelius displaying the routes of individuals travels and more scientific ones such as those of Athenasius Kircher in particular, but none were measured.

The newly formed Royal Society took a great interest in cartography and encouraged many an early work. Some cartographers were even members, notably Joseph Moxon who was joined on the day of his election by his good friend Halley. Edmond Halley is of course most well known for the comet named after him, but like many of the natural philosophers of his day his interests and skills stretched far and wide. Indeed he was regarded by Nature in 1880 as second only to Newton in the Anglo Saxon world.

Halley was born 29 October 1656 in Shoreditch, north east London, then in the country. His father of the same name was a prosperous soap manufacturer. He went to St. Paul’s School in London which counted among its old students the likes of John Milton and Samuel Pepys. It was whilst at school that Halley first measured the variation of the compass. In 1673 Halley entered Queen’s College, Oxford. Whilst still an undergraduate he published the first of some eighty papers in the Philosophical Transactions on the problem of determining the orbit of a planet. In the same year he wrote to the Royal Society about the feasibility of producing a star catalogue of the southern hemisphere. It would compliment that of the north produced by the likes of Hevelius, Cassini and Flamsteed. Approved by the King, Halley left for St. Helena for a year and produced a catalogue of over 340 stars which was published in 1678. His meeting with Newton in 1683 was instrumental in the publication of the ‘Principia Mathematica’, Halley paid for the printing. In 1686 he published what is considered the earliest meteorological chart in the Philosophical Transactions. It has no title but is often called his ‘Chart of the Trade Winds’.

From the early 1690s Halley had been negotiating with the Royal Society for the use of a ship on a voyage of scientific discovery. Granted the rank of Captain in the Royal Navy and with royal approval he set sail in the Paramore in 1699. The purpose of the voyage was to measure the variation of the compass throughout the Atlantic Ocean. The compass variation itself also varied, something we call the declination and secular variation. As mentioned above Halley had studied this phenomenon before. He was hoping that a more measured approach over a large area might formulate a method of determining longitude, the holy grail of navigation. Halley’s sea voyage was the first undertaken for purely scientific purposes.

The Paramore returned to England in early September 1700. Shortly after he published this map which contained about 150 observations. It is credited with being the first printed map to show isogones or lines of equal magnetic variation. Indeed it is the first to introduce the idea of lines connecting equal values. Since then isolines (lines connecting points of equal intensity) are found in all sorts of maps. Isobaths (lines of equal depth), contours (lines of equal elevation), isotherms (lines of atmospheric temperature) and isobars (lines of equal air pressure) are amongst the approximately one hundred created.

There is no date on the map but the finished version is dedicated to King William III who died 8 March 1702. The Journal Book of the Royal Society bears an entry on 4 June 1701 “Mr. Halley presented the Society with a map of his late voyage to the South. He was thanked for it and it was ordered to be hung up in the meeting room.” This almost certainly refers to a printed version and therefore a date of 1701 is always given. The cartouche upper left explains “The Curve Lines which are drawn over the Seas in the Chart, do shew at one View all the places where the Variation of the Compass is the same; The Numbers to them do shew how many degrees the Needle declines either Eastwards or Westwards from the true North …”. The track of the Paramore is shown and illustrating its southern path are icebergs and sea creatures. The latter’s identity has been hotly debated. The whole is laid out on a Mercator projection.

Its rarity is also recorded, it was all but lost to cartobibliographers until rediscovered in 1895 by the American geophysicist Louis A. Bauer. Chapman states “Gradually the copies of Halley’s charts became out of date [as the declination varied], and most of them were worn out with use, until few remained; of these a small number found their way into great libraries, and perhaps some still lie forgotten and undiscovered in public or private hands. In 1870 Sir George Airy (1801-1892), another famous Astronomer Royal at Greenwich, who shared the geomagnetic interests of his predecessor Halley, remarked that reference was often made to Halley’s Magnetic Chart, but that he ‘had not ascertained that any writer had ever seen it.’ ‘As I was desirous’ (he wrote) ‘of making myself acquainted with a document so important in the history of magnetic science, I made enquiries in nearly every Academy in Europe, but could not find anywhere a copy of this Chart.’

It was shortly after this period that Halley’s greatest claim to fame was published. In 1705 a paper he wrote for the Philosophical Transactions using Newtonian physics predicted that a comet he had seen in 1682 would return again every seventy-six years. It did, after his death, and it has been known by his name ever since. It had a profound effect on allaying popular fear of these celestial events. Halley died 14 January 1742 aged 85. He remained to his death a captain in the Royal Navy, Savilian Professor of Geometry at Oxford and Astronomer Royal.

The example offered here is dedicated by hand “To the honble. Dennis Lyddall Esqr.Comr: of his Majties. Navy This CHART is humbly presented by his Honrs most obedt. Servt Edmd. Halley”. The Minutes of the Navy Board for the morning of Wednesday 7 May 1701 record “Admty Ordr of the 5th for paying to Capt Edmd Halley out of the tenths of Prizes the sum of 200 in consideration of his great paines & care in a late Voyage he made for the discovering the Variation of the Needle … Give a Copy to Mr Lydell”! A footnote identifies Dennis Liddell as Controller of the Treasurer’s Accounts. A comparison of the handwriting would appear to indicate that this is in Halley’s hand. This is clearly a more formal hand that one he would use to sign letters but there are enough similarities to substantiate the belief. Similarly who else would word it in such a way.

State 1 – Proof without dedication or publishers imprint engraved by John Harris. Locations: William Andrews Clark Library, Los Angeles; Royal Geographical Society; this example. Only known examples.

State 2 – The dedication to William III is engraved in the previously empty cartouche to the right. However there is still no publishers imprint. British Library.

State 3 – With imprint of “Sold by R. Mount and T. Page on Tower Hill London” below the lower left cartouche. Examples Royal Astronomical Society; Royal Geographical Society; Library of Congress

Circa 1713 – A later issue includes additional text pasted on as side panels. These bear the imprint of R. and W. Mount and T. Page. Richard Mount’s son William joined the firm about 1712.

Circa 1722 – A later issue still includes text panels which are entirely re-set bearing the imprints of William Mount and Thomas Page (Fig. 7). Richard Mount died 29 June 1722 after being kicked in the leg by a carthorse on London Bridge.

Chapman, S. (1941) “Edmond Halley as physical geographer and the story of his charts”, Occasional Notes no. 9, Royal Astronomical Society; Robinson pp. 46-51, 84-6; Thrower, Professor Norman (1978) “Edmond Halley and Thematic Geo-Cartography” in The Compleat Plattmaker, pp. 195-228; Thrower, Professor Norman. (1980) “The Three Voyages of Edmond Halley in the Paramore 1698-1701”, Hakluyt Society pp. 55-9, 322 (minutes), 368-9 & fig. 10 for a sample of his handwriting; Thrower, Professor Norman. (1986) “English Mapping of America 1675-1715”, in The Mercator Society, Publication Number One (illustrating the Clark Library copy); Thrower, Professor Norman “Maps & Man. An Examination of Cartography in relation to Culture and Civilization” fig. 6.3.