A FUNDAMENTAL THEMATIC MAP. It is difficult to overestimate the importance of this chart. We hear a lot about the importance to navigation of understanding longitude but the tides produced just as much of a headache. Their causes and the variations around the globe were not understood and it caused heavy losses of life. Halley’s last voyage in the “Paramore” produced a map of the English Channel which for the first time enabled a prediction of the tides. He used a series of roman numerals across the map to indicate the hour of the high tide. By a computation described in the “Advertisement” the precise hour of the day could be computed for each area. As was Halley’s great strength he again managed to bring something that was so complicated down to a level that was understandable. A study of many charts published in the ensuing years has revealed the following list of maps was issued in the immediate period following Halley’s Channel voyage.

1 – A Large Chart of the Channell between England and France … 1702. Richard Mount & Thomas Page. Engraved by John Harris delineated by Joel Gascoyne. In three sheets 605 x 1355 mm. The far right sheet bears an inset of the Solent, an “Advert” in the same explains the chart. Found in the “English Pilot First Part” 1701 and 1702. Sanderson “Atlases in the National Maritime Museum” 423 nos. 69-71; Shirley “Atlases in the British Library” M.M & P 1a no. 9a.

2 – A New and Correct Chart of the Channel between England and France. No date, published by Mount & Page? and with no engravers name. In two sheets each 630 x 480 mm. The right sheet bears insets of Plymouth harbour and the Solent. Example in the Royal Geographical Society. Illustrated in Thrower, “The Compleat Plattmaker” fig. 4 p. 223; Thrower “The Three Voyages of Edmond Halley in the Paramore 1698-1701”, fig. 9 and supplement facsimile.

3 – A New Chart of the Channell Between England and France… R. Mount & T, Page. No date. Engraved by Herman Moll, 450 x 575 mm. Title top centre, advert lower right. Found in Mount & Page’s “Atlas Maritimus Novus” 1702 of which examples reside at the Library of Congress, Harvard, National Maritime Museum and the Admiralty. It is also seen in the 1708 edition residing at the British Library. Howse & Sanderson p. 80; Shirley “Atlases in the British Library” M.M & P 13a no. 7.

4 – A New and Correct Draught of the Channell between England and France… 1701. John Thornton. No engraver, 430 x 830 mm. With insets of the Isles of Scilly, Plymouth, the Solent, Thames Estuary and St. Malo. Published in the “English Pilot Third Part”, 1703. Shirley “Atlases in the British Library” M.Thor 1c no. 7.

Norman Thrower, who has written more on Halley’s charts than anyone in the modern era believes that the example at the Royal Geographical Society (number 2 above) is the first published chart to record his findings. However he does not appear to state why he believes it to be so. I believe we can safely rule out the third above as it is a single sheet chart, one would assume with larger charts in competition that it would be one of these that held the title of being the first. The fourth in the list is by Thornton and is also more of a functional chart for the open market. Also Thornton is someone that Halley had not worked with before. He had worked with Mount and Page on the chart of the Atlantic Ocean showing the variations of the compass and we would be safe to assume that this chart issued barely a year later would have been entrusted to the same hands. Therefore the honour falls to either the two sheet chart identified by Thrower (number 2) or this three sheet map (number 1).

The engraver of Halley’s great Atlantic chart of 1701 is John Harris, the same engraver produced this three sheet map. The wording of the title similarly gives a clue. The second, a two sheet map refers to it being an existing chart being improved: “with considerable improvements not extant in any Draughts hitherto Publish’d”, no such link is made in the three sheet: “Done from the Newest, and Best Surveys; with the flowing of the Tydes, and Setting of the Current, as they were Observed in the Year 1701. by Capt: Edmund Halley”. Both are published by Mount and Page but the second is more manageable and useable in size. The first published work would not be too concerned about such an issue. One further key point is the presence of the magnetic variation on the three sheet which is omitted on the two sheet. A nearby legend describes it in greater detail. The three sheet names Joel Gascoyne as the delineator. Gascoyne was a noted Thames School chartmaker and could have quite reasonably been hired by Halley to utilise his knowledge of the cartography of the Channel. His name however is not mentioned again on any other chart. It is my conclusion that it is highly probable that the three sheet chart drawn by Joel Gascoyne and engraved by Edmond Halley is indeed the original chart to record the tides produced by Edmond Halley. The example we offer here is only the one western sheet displaying the waters off Cornwall, a sheet of great importance to the navigators of the day. Howse & Sanderson p. 80; not in ‘Scarcer Maps of the Isles of Scilly’; Sanderson “Atlases in the National Maritime Museum” 423 nos. 69-71; Shirley “Atlases in the British Library” M.M & P 1a no. 9a; Thrower, “The Compleat Plattmaker” pp. 220-5; Thrower “The Three Voyages of Edmond Halley in the Paramore 1698-1701”, fig. 9 and supplement facsimile.