The collections of the Library of Congress include thirteen early nautical or portolan charts published between 1320 and 1734. Cartographic historians and map librarians are familiar with these early charts. But what, exactly, is a “portolan” chart? This post will attempt to address a few of the basic ideas revolving around these early nautical charts.
The term portolan refers to a graphic representation of written sailing directions. Today, when traveling to and fro we often use a map or, more recently, GPS programs found on smartphones and other electronic devices. In the 13th, 14th, and 15th centuries, however, those planning, navigating, or reporting on explorations would simply describe the journey in a written form. Gradually, these written directions were translated into geographic depictions on vellum (or some other animal skin) that included place names, primarily perpendicular to and along the coast. This offered navigators a more effective visual device for establishing direct-line sailing directions when planning a voyage.
Most importantly, portolan charts incorporated a series of compass roses which provided information on a course or bearing. If, for example, one wanted to sail a vessel from Rome, Italy, to North Africa using a portolan chart (see detail above), the captain of the sailing vessel would find the appropriate course and bearing as shown on the chart. The captain would then instruct the helmsman (the person steering the vessel) to sail “due south”, a bearing of 180 degrees as shown on the compass rose. Portolan charts provided a very practical method of navigation.
It is important to note that while some vellum portolan charts were used aboard ship as aids to navigation, others were purely decorative. Additionally, they may have been prepared with elaborate decorations as “presentation” copies in order to impress royalty, clergy, important merchants, or others. One of the Geography and Map Division’s treasures is a 1544 set of ten manuscript charts bound in a leather binding attributed to the Venetian cartographer Battista Agnese (ca. 1500-1564). The first chart (see above) covers the Atlantic Rim, or those countries bordering the Atlantic Ocean, as well as Africa and the Arabian peninsula. Interestingly, Africa and the Arabian peninsula are separated by a water body colored red – the Red Sea! The map also appears to depict the Gulf Stream along the east coast of America.
The inclusion of the Gulf Stream is certainly decorative but may also be speculative, especially since hydrographic evidence of its existence was not published on a chart until 1768. Given the feature’s somewhat vegetative appearance, it may also be an early attempt at illustrating the Sargasso Sea.
While not a portolan chart, there is a second world map included in the Agnese atlas which shows the 1519-1522 circumnavigation of the world by the Portuguese explorer Ferdinand Magellan (ca. 1480-1521). Magellan left Spain in 1519 and, even though he died along the way, his crew returned to Spain in 1522 thereby completing the very first world circumnavigation.
Portolan charts in the collections of the Library of Congress and other institutions served as the predecessor for nautical charts issued today. These historical charts represent some of the earliest, and most informative, methods to document early journeys of exploration.