Pliny gives[161] an account of two different occasions when observations were made of the same eclipse at two different places. He says that at the time of the battle of Arbela the moon was eclipsed at the second hour of the night, when at the same hour it was rising in Sicily. He also speaks of an eclipse of the sun that was seen in Campania between the seventh and eighth hours and in Armenia between the eleventh and twelfth, indicating a difference in longitude of four hours, or 60°. The actual distance is no more than half of this. Ptolemy also cites[162] the eclipse of 331 B. C. as giving the distance between Carthage and Arbela. We shall see later that much greater accuracy was attained by the Arabs in their calculations of longitude and that some of their figures were passed on to the Western world in astronomical tables during the twelfth and thirteenth centuries. CARTOGRAPHY Little need be said of the cartography of antiquity,[163] for although medieval maps undoubtedly owe much to classical predecessors, none of the classical maps which were destined directly to influence the cartography of the Middle Ages have come down to us. Indeed we have good copies of only two. These are the maps of Ptolemy and the so-called Tabula Peutingeriana,[164] or Peutinger Table. Ptolemy’s maps exerted no influence whatever on the cartography of the age of the Crusades.[165] The Tabula Peutingeriana is preserved in a manuscript of the twelfth century or earlier and probably was originally copied from a large chart showing the main routes and provinces of the Roman Empire. It is an extremely long and narrow affair in which the geography is woefully distorted. Though in itself hardly representative of the best in the Roman cartographer’s art, the original may have been compiled from a contemporary Roman map of the world and adapted through its long and narrow form to the especial purpose of illustrating itineraries. We know that maps of the world were officially drawn in imperial Rome and posted up for the benefit of the public: the one constructed by the order of Agrippa and Augustus in the Porticus Octaviae was the most famous;[166] and others are mentioned in literary sources.[167] Certain medieval maps of the world are possibly related to some of these Roman charts,[168] but unfortunately in the absence of the Roman maps themselves the exact relationships cannot satisfactorily be worked out. Although the ancient astronomers knew a variety of projections for representing the heavens—stereographic, orthographic, and others[169]—these were not applied to maps of the earth until long after our period. Ptolemy describes several projections, among them the conic, which he may have used; but there is no question of any mathematical projections in the twelfth and thirteenth centuries, and none of the cartographers of that period took account of the fact that they were endeavoring to show a globe on a flat surface.