Single sheet. Sheet 4 from a set of 6 comprising: A chart of North and South America, including the Atlantic and Pacific Oceans, with the nearest coasts of Europe, Africa and Asia. Engraving coloured in outline. Scale: [circa 1:15,000,000]. Mercator projection, prime meridian through Ferro, with longitude from London added. Graduated for latitude and longitude. Outline colour denotes the discoveries and settlements of colonising nations. The chart contains tables of geographical positions.

In 1753, when Thomas Jefferys published this chart, there was no reliable method for finding longitude at sea and the Board of Longitude was offering a reward of £20,000 for solving the problem. The lunar distance method and the timekeeper method were the leading contenders. At the same time, improvements in astronomy and observational instruments meant that measurements of co-ordinates on land were becoming more reliable. Jefferys attempted to make his charts as accurate as possible and so published the co-ordinates of places recorded by named observers to make it clear if there was any disagreement about them, as with Jamaica, for example. When William Harrison returned from a voyage to Jamaica in 1763 and reported that his father John Harrison's timekeeper H4 had performed well enough to win the prize, the Board of Longitude objected that the longitude of Port Royal was not fully known. Green published an accompanying volume, in the NMM library catalogue at PBD8625.