Beinecke Rare Book and Manuscript Library, Yale University, New Haven, Connecticut.

Jorge de Aguiar’s chart, signed and dated 1492, is a Mediterranean chart expanded to include the Atlantic, which occupies almost one-third of the chart. The illuminations are not as prominent, nor as rich as those on highly illuminated Mediterranean charts, but their presence on this chart reveals that chartmakers in Lisbon produced higher-end charts for patrons who commissioned them. The center point is readily apparent—it is decorated with a large compass rose.  Aguiar placed it near Algiers, and he painted a sixteen-point compass rose over it. Where the circumference of the invisible circle lies can be determined by looking for the compass sub-roses. Six sub-roses appear over intersection sub-points on the invisible circumference. The invisible circle encloses most of England and Ireland in the north, most of the western Mediterranean in the east, and just past Cape Verde in the south. In the west, it cuts through the Atlantic where two intersection sub-points and two decorative compass sub-roses are prominent. In the interior of West Africa, Aguilar inserted an additional piece of coastline onto the charts, in order to expand the geographic information. With this piece of coastline, Aguiar extended the chart from Sierra Leone to São Jorge da Mina. The additional piece of coast includes toponyms, a landscape illustration, three palms, and a cityscape, over West Africa. In a GIS, this piece of coastline can be reattached to show the full extent of the chart. To consult the chart in the Beinecke Library, click here.