Portolan Chart of Western Europe Showing the British Isles(001ADD000022018U00005000)
Cartographer: Martines, Joan
Medium: Ink and pigments on vellum
This is a portolan chart from a bound atlas, showing the British Isles. It is by a chart maker called Joan Martines from Messina, Italy and dates from 1579. Invented by mariners, Portolan charts take their name from the Italian ‘Portolano’, meaning a written description of a coastline. The first Portolan Charts date from the late 13th century and represent an important change in the use of maps and charts. Until this point, most maps had held a religious significance and purpose, such as the medieval mappa mundi which was based on theological beliefs. The Portolan chart contrasts with this tradition as they are based on scientific observation and first hand experience and have a practical purpose. Reflecting their use by sailors they note only coastal locations, omitting most of the internal detail of the land. Place names are written at right angels to the coast, the more important ports in red ink. The lines which cover this and all other portolan charts are lines of constant bearing known as rhumb lines. These radiate from compass roses and allow the sailor to plot a course from harbour to harbour using dividers and straight edge. This portolan shows post 1550 developments in the representation of the British Isles, in that it includes an indentation on the coast of Wales, showing knowledge of the Bay of Cardigan. However, knowledge does not extend to include the Lleyn Peninsular. Scotland is still presented as an island. Crosses adjacent to the coast indicate rocks in the shallow waters, which sailors would wish to avoid.