MARCIANUS (c. A.D. 400), Greek geographer, was born at Heraclea in Pontus. Two of his works have been preserved in a more or less mutilated condition. In the first, the Periplus of the Outer Sea, in two books, in which he proposed to give a complete description of the coasts of the eastern and western oceans, his chief authority is Ptolemy; the distances from one point to another are given in stades, with the object of rendering the work easier for the ordinary student. In this he follows Protagoras, who, according to Photius (cod. 188), wrote a sketch of geography in six books. The work contains nothing that cannot be learned from Ptolemy, whom he follows in calling the promontory of the Novantae (Mull of Galloway) the most northern point of Britain. Improving on Ptolemy, he makes the island of Taprobane (Ceylon) twenty times as large as it is in reality. The second, the Periplus of the Inner Sea (the Mediterranean), is a meagre epitome of a similar work by Menippus of Pergamum, who lived during the times of Augustus and Tiberius. It contains a description of the southern coast of the Euxine from the Thracian Bosporus to the river Iris in Pontus. A few fragments remain of an epitome by Marcianus of the eleven books of the Geographumena of Artemidorus of Ephesus.
See J. Hudson, Geographiae veteris scriptores graeci minores, vol. i. (1698), with Dodwell’s dissertation; C. W. Müller, Geographici graeci minores, vol. i. pp. cxxix., 515–573; E. Miller, Périple de Marcien d’Héraclée (1839); S. F. G. Hoffmann, Marciani Periplus (1841); E. H. Bunbury, Hist. of Ancient Geography (1879), ii. 660; A. Forbiger, Handbuch der alten Geographie, vol. i. (1842).