The second group is made up of simple representations of the three continents, often called T-O maps (Figs. 1a-1b). On these the known world is shown as a circle within which a T is drawn dividing it into three parts. East is at the top. The upper compartment, that above the crossbar of the T, represents Asia; the two lower compartments, Europe and Africa. The surface is usually unadorned with vignettes or conventional symbols of any sort, and the legends are reduced to a minimum. It seems likely that Augustine had before him such a diagram when he wrote a passage in _De civitate dei_ which describes to perfection the division of the known world as the T-O maps show it, and it may well be that the map which Orosius must have used when he wrote the geographical chapter of his history was a modified example of the same type. An extremely large number of T-O maps are to be found in codices dating from the eighth century onward, illustrating the writings of Isidore, Bede, Raban Maur, and others.[294] [Illustration: FIG. 1—Types of T-O and Sallust maps. (Figs. 1a and 1b from Santarem, _Essai_, 1849–1852, atlas, vol. i, pl. 5, figs. 5 and 1; Fig. 1c from Miller, _Mappaemundi_, vol. iii, 1895, fig. 43.) ] _Sallust Maps_ Closely akin to the T-O maps, but somewhat more elaborate, are the sketches of the third group (Fig. 1c). These accompany manuscripts of Sallust’s works and may have been drawn to illustrate a passage in Sallust’s _De bello Jugurthino_ describing briefly the countries of the known world. The T-O form is carefully followed, but legends and pictures add a touch of life. The oldest example (tenth century) is strictly classical and fails to show Jerusalem, a stock feature in most medieval maps. Later specimens reveal the influence of the Christian tradition, and upon them Jerusalem figures as an immense church or castle.[295] _Beatus Maps_ The fourth group is by far the most interesting. In the latter part of the eighth century a priest, Beatus, of the Benedictine abbey of Valcavado in northern Spain wrote a commentary on the Apocalypse, destined to become very popular in later times. To demonstrate graphically the division of the world among the twelve apostles, which is spoken of in a passage included in this commentary, either Beatus or one of his contemporaries drew a map. Though the original of this is not now extant, no less than ten subsequent maps for which it served as a model are preserved in manuscripts of the tenth century and later. The researches of Miller[296] have shown that three of these ten were probably derived from a fairly full and faithful copy of the original, but that the others represent merely a generalized outline. The best example, the so-called St. Sever map, dating from about 1050 and now in the Bibliothèque Nationale at Paris, displays an immense wealth of detail, legends, vignettes, and pictures of all sorts (Fig. 2).