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Longitude is indicated in two different ways on this mid-18th century map: along the top border, it is shown in degrees (number of degrees east of London); more unusually, along the bottom border, it is shown in time (number of hours east of London).

This map from 1800 is by the Scottish cartographer Alexander Dalrymple, who was the first Hydrographer of the British Admiralty. It documents the river systems of the Birman Empire (Myanmar) and modern Thailand, Laos, Cambodia and Vietnam.