News

Day 4 of ‘Looking for the Longitude’: ‘how to draw a line of longitude’

  • 18 June 2016

Location: Royal Society

‘A New and Correct Chart of the Atlantick Ocean reduced describing part of the Coasts of Africa and America with their adjacent islands’ from Atlas Maritimus et Commercialis, 1724, engraving , 51 x 59cm

National Maritime Museum, Unknown,, ‘A New and Correct Chart of the Atlantick Ocean reduced describing part of the Coasts of Africa and America with their adjacent islands’ from Atlas Maritimus et Commercialis, 1724, engraving , 51 x 59cm

The first problem was how to draw a line of longitude on a map, what projection to use, and indeed where to draw your meridian. Mapmakers and natural philosophers published pamphlets discussing the merits of different projections, critiquing others, and illustrating their own. Henry Wilson and Thomas Haselden disagreed in particular over Wilson’s “globular” projection, culminating in Wilson’s chart of the Atlantic published with mapmaker and dictionary printer John Senex in 1728.

Hogarth’s lunatic draws his map carefully on the wall, but it is problematic. The slanting projection does not sit firmly on the plane of the wall, its latitude lines curve away from their courses, with the equator completely removed. He labels two of the great geographical dreams of the time: the possibility of reaching the North Pole, and the existence of a great, unknown southern continent in the Antarctic Circle.

Read day 4 by expert Katie Parker, Hakluyt Society, on maps and the London map trade