T-in-O Maps

The label T-in-O maps, or simply “T-O maps,” is the modern name given to a simple world map found in a variety of sources during the Middle Ages. They appear as explicit graphics (i.e., diagrams made with circles and straight lines with [Page 2845]names attached), as the structure underlying far more complex maps (e.g., the Hereford mappa mundi has one as its underlying structure for the continental landmasses), and as symbolic representations of the earthly, human, sublunar world (e.g., it inspired the “royal orb” that is or was part of the regalia of European royalty, and in that form, it can be found linked to many Christian statues). In form, the T-O map is a circle with its horizontal diameter marked and with a radius perpendicular to that diameter running down to the lowest point on the circle. The diagram looks like a “T” inscribed in an “O,” hence its modern name. East is at the top of the circle. The upper half represents Asia, the lower quarters Europe (left) and Africa (right). The outer circle is the Ocean; the left radius represents the Danube (although it is commonly misidentified as the Don); the right radius represents the Nile and the lower radius, the Mediterranean. It portrays the whole of the inhabited world, in the northern temperate zone, as it was known to the Europeans.

Figure 1 Model of a typical T-in-0 map. Common in medieval Europe, T-in-0 maps divided the known world into three continents along biblical lines.

Source: Author.

Other details are often added to the basic map. There is a more elaborate form showing the Danube's mouth; often the continents are shown with the names of the children of Noah (see Genesis 10) from whom the African (from Ham/Cham), Asian (from Shem/Sem), and European (from Japhet) nations were believed to have descended; and often one or two local details (e.g., the Pillars of Hercules [Gibraltar] or the British Isles) are shown.

The map has to be read in conjunction with other geographical diagrams to appreciate it fully. The most important of these other drawings is the zonal map, which has a torrid zone at the equator, frigid zones at the poles (both uninhabitable), and between them a northern temperate zone (which is the area covered by the T-in-O map) and a southern temperate zone, in which it was assumed that there was a corresponding landmass but there was a debate as to whether or not it was inhabited (the antipodes were its putative inhabitants). When this consideration is taken into account, the T-in-O map can be seen not as that of a “flat Earth” but as an attempt to portray lands on a sphere as seen from a great distance. As such, it embodies elements of an orthographic projection; however, insofar as it has the eastern end of the Mediterranean at its center and the ocean as the circumference, it has elements of an oblique azimuthal projection. It was this aspect of this map, when read in conjunction with certain biblical passage (e.g., Ezekiel 5:5) that led to the practice of placing Jerusalem at the center of many medieval maps.

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