The scientific genius of the Alexandrian Greeks of the Hellenistic period showed itself in the work of men like Eratosthenes and Hipparchus. By them the mathematical and astronomical aspects of geography were developed with accuracy; but unfortunately, owing to the almost universal ignorance of Greek in the West, the products of their genius had little part in the molding of medieval theories. ROMAN INFLUENCE ON GEOGRAPHY The Roman conquests tended to discredit scientific investigations and to bring into favor works of a descriptive nature which would appeal to the military chief, the provincial governor, or man of the world—to the practical rather than speculative type of mind. Polybius regarded geography as an important auxiliary science to politics and history. The geographical portions of his history treat of the countries of the known world, their peoples and customs; he is not concerned with the size and shape of the earth nor with the determination of latitudes and longitudes. Strabo, writing at the time of Augustus, represents the culmination of the Polybian method; but his great and comprehensive work, though of first importance in the history of ancient geography, was not read at the time of the Crusades. PTOLEMY The Greek, or more purely scientific, attitude, however, did not completely succumb. Posidonius[3] in the first century before Christ reverted to the method of Eratosthenes; and with Marinus of Tyre and Claudius Ptolemy, in the reigns of Trajan and Hadrian, there came a revival of mathematical geography which almost, if not quite, equaled the high level reached by the Alexandrians[4]. Ptolemy was the author of two works, both of which were destined profoundly to modify the development of science in later ages. These were the _Mathematical Composition_ (or _Almagest_, as the Arabs called it), a treatise on astronomy, knowledge of which reached the medieval West through Moslem channels; and the _Geography_, a work which remained virtually unknown in Europe until the fifteenth century. LATIN WRITERS: PLINY, SOLINUS, CAPELLA, MACROBIUS