Common features of most of the Dieppe world maps (see Vallard 1547, Desceliers 1550) are the compass roses and navigational rhumb lines, suggestive of a sea-chart. However, the maps are best understood as works of art, clearly intended to be spread out on a table, and containing information on the latest discoveries, side by side with mythological references and illustrations. For example, the Desceliers 1550 map carries descriptions of early French attempts to colonise Canada, the conquests of Peru by the Spanish and the Portuguese sea-trade among the Spice Islands. On the same map can be found descriptions of legendary Cathay, king Prester John in Ethiopia, and the race of Amazons in Russia. Other Dieppe maps also carry fictitious features such as the Marco Polo inspired Zanzibar/Îles des Geanz. (see Vallard 1547, Rotz 1542 and Dauphin c. 1536–42). As with other maps made before the 17th century, the Dieppe maps show no knowledge of longitude. While latitude could be marked in degrees as observed by astrolabe or quadrant, easting could only be given in distance. Mercator's projection first appeared in 1568–9, a development too late to influence the Dieppe cartographers.