Exceedingly Rare "Navigational" Chart of the North Atlantic from London’s Foremost Chartmaker
Striking and very rare chart of the Atlantic on an unusual projection by John Thornton. The chart is known in only two institutional examples.
The chart covers much of the North Atlantic, ranging from Newfoundland to Brazil in the west and from England to the Gulf of Guinea in the east. The focus ot the chart and text at the top center would seem to be navigational issues concerning North America, with a discussion of routes between England and Cape Codd and from Cape Henry, Virginia to the Lizard (a reference to Lizard Point, the most southerly on the British mainland).
The chart is on a split projection that resembles globe gores. Thornton was a highly-trained and much sought-after chartmaker who worked closely with the leading navigational teachers and mathematicians of the day. He participated in debates as to the best way to project a chart and this example can be an educational tool. The production of this chart as a tool of navigation is intriguing and was perhaps intended to assist navigators at sea by offering a visual tool to illustrate the unreliability of certain types of charts for long distance blue water sailing.
The chart is intended to lay bare the limitations of the plain chart and the necessity for charts that take into account the curvature of the earth, especially toward the poles, and the effect of this curve on the distance between meridians. The text at the top center reads:
By this Chart may be seen the Error of Plaine Saileing, shewing how Impossible it is to laye down 3 places which differ both in Lattd. and Longd. in there [sic.] true course and distance from Each other on the plaine Chart, and the greater distance from Each other, and the nearer the poles, the greater the Error.
In this Chart, Cape Codd in New England (if Laid down in it's [sic.] true Distance from England) ought to lye near the Merridian of Barbados (as it was formerly Laid) but it is found by Experience, that Cape Codd lyes near a point of the Compass more westerly, as in this Chart it is Laid down which makes the Distance to Long from England. to help which take notice of These Two Curve lines the distance between which is to be allowed in measuring all distances from England, and then it will be found to come near the truth
Suppose you are minded to Measure the Meridian distance between Cape Henry in Virginia and the Lizard. Extend your Compass from Cape Henry in the Lattd. of 37 deg: to A: on the Nearest Curve in the same Lattd. and from B: on the other Curve in the Same Lattd.: to the Lizards Merridian, those two distances measured on the Graduated Merridian, and Added togeather is the Distance Required. Or if you take the Distance between the Two Merridians at once, and deduct the Distance between A: and B: on the Curves it will be the Same.
While the chart makes for a fine visual aid, it is not as easily manipulated as the Mercator Projection. To the extent it was actually intended for use at sea, it appears to have had a short lifespan, as it was quickly replaced in about 1706 by another chart by Samuel Thornton, John’s son. A New and Correct Chart from England to Guine : with all the Tradeing part of the West Indies, According to Mr. Edwd. Wrights projection vulgarly called Mercators Chart is, as the title explains, on the Mercator projection and credits Edward Wright—at this time the Mercator projection was better known in England by Wright’s name, who had popularized it at the close of the late sixteenth century.
The map survives in only two recorded examples, one loose sheet and one example in a circa 1704 edition of the Atlas Maritimus collection of the British Library. The Atlas Maritimus was an influential nautical atlas initially planned and produced by John Seller in 1675. However, Seller was notoriously too ambitious and therefore unable to bring large projects to fruition. By 1677, facing bankruptcy, Seller had to seek partners, which he found in William Fisher and John Thornton. The partnership, which also included navigation teachers James Atkinson and John Colson, took over the production of Seller’s works, including the English Pilot and the Atlas Maritimus. Together, they produced another Atlas Maritimus in 1677-8. The combine dissolved, however, in 1679, leaving the members to release their own versions of the atlas. Thornton brought out his own editions of the Atlas Maritimus from the mid-1680s until his death in 1708.
The chart is extremely rare.
This would seem to be the third known example of the chart (the others being held by the John Carter Brown Library and the example bound into the Atlas Maritimus in the British Library (Maps C.25.b.9.(17)).
We believe our example may be the example of the chart offered by Magna Gallery in 1985.
John Thornton was a respected and prominent chartmaker in London in the latter part of the seventeenth century. He was one of the final members of the Thames School of chartmakers and served as the hydrographer to the Hudson's Bay Company and the East India Company. He produced a large variety of printed charts, maps, and atlases in his career, but he was also a renowned manuscript chart maker. Born in London in 1641, he was apprenticed in the Drapers Company to a chartmaker, John Burston. After being made free of the company (1665), he was part of the combine that took over John Seller’ English Pilot in 1677. Thornton was trusted by the naval and navigational establishment of the day; one of his clients was Samuel Pepys, naval administrator and diarist. Thornton died in 1708, leaving his stock to his son, Samuel, who carried on the business.
Samuel, born in ca. 1665, also had apprenticed in the Drapers Company and was made free a year after his father’s death. He continued the business until 1715, when he died. His stock then passed to Richard Mount and Thomas Page.