This 1745 map of Korea was prepared for a universal history published in France in the 18th century. Based on an earlier English map, it is mainly in French but includes some names in German, e.g., “Das gelbe Meer” for the Yellow Sea. The notation at the bottom indicates that the prime meridian is set at Ferro Island, otherwise known as El Hierro, the southwestern-most of the Canary Islands. In his Geographia, the ancient astronomer and geographer Ptolemy (87-150) specified that maps should use coordinates stated in degrees, with the prime meridian -- 0º -- passing through the Fortunate Islands. The latter were a group of islands, referred to in classical Greek and Roman literature, which may or may not have been the Canary Islands. Following Ptolemy, in 1634 Cardinal Richelieu, first minister to the King of France, decreed that Ferro Island be established as the prime meridian. This practice was followed on French and other maps for many years. In 1884 an international convention established Greenwich, London, as the prime meridian, the practice that remains in use to the present day.