By no means all the geographical knowledge and thought of the Crusading age could be stated and discussed in a volume of even many times the size of this. It is the writer’s hope that the materials selected are sufficiently diverse to give a rounded and just, though it be necessarily far from complete, understanding of the geographical lore of a significant period in the history of science and of civilization. PART I ORIGINS, SOURCES, AND PLACE IN THE CLASSIFICATION OF KNOWLEDGE OF THE GEOGRAPHICAL LORE OF THE TIME OF THE CRUSADES CHAPTER I THE CONTRIBUTION OF THE ANCIENT WORLD _SOURCES_ THE PYTHAGOREANS, PLATO, AND ARISTOTLE The earliest writers who dealt with geographical matters in a more or less scientific spirit were the Greeks of Ionia and the Pythagorean philosophers of Magna Graecia. Though their theories exerted no direct influence on the formation of medieval geography, they should not be entirely overlooked. Ionic geography gave many ideas to the later Greeks; Pythagorean thought brought to bear a strong influence on the Platonic cosmology, which reached the Middle Ages through the Latin translation of Plato’s _Timaeus_ made by Chalcidius early in the fifth century after Christ, and through the Platonists Martianus Capella and Macrobius. Until the middle of the twelfth century Plato, of all philosophers, held the strongest grip on medieval thought; after that time the influence of Aristotle became more potent in the framing of the scholastic conception of the universe. We must regard Plato and, even more, Aristotle as the indirect sources of most of the cosmological, physiographic, and meteorological knowledge which, elaborated by later writers of antiquity and by the Moslems, reached the Middle Ages at second hand. Among the many writings of Aristotle those which contain the most material of interest to the geographer are the _De caelo_ (Περὶ οὐρανοῦ) and the _Meteorology_. The former, in four books, treats of the properties of the heavenly bodies, of the elements, and of the earth. Translations of the _De caelo_ in the Middle Ages often went under the title _De caelo et mundo_.[1][2] The _Meteorology_, besides a detailed discussion of the phenomena of the atmosphere, includes many speculations on physical geography. Theories of cosmology also found expression in the _Physics_ and _De generatione et corruptione_. Footnote 1: The notes will be found at the back of the book grouped by chapters and consecutively numbered within each chapter.