Page:Popular Science Monthly Volume 16.djvu/514

488 men's tales. Having thus disposed of the anterior belief, he proceeds to give his own idea of the earth, which he says no true Christian can doubt. It was, that the earth was an oblong plain, inclosed at its four extremities by huge walls of immense thickness, on which the firmament or vault of the heavens rested; and that near the north pole there was a high mountain, around which the sun, the moon, and the stars turned, the intervention of which mountain, at certain periods, caused eclipses.

We have now approached a period when Europe sank into the deepest ignorance, communication between places was broken up through the long continuance of wars; roads were destroyed, there was little or no commerce, for traveling was difficult and dangerous, and people in close proximity knew comparatively nothing of each other. Fortunately, however, this was not the state of things throughout the world. During the period that marks the rise, the maturity, and decline of the empire of the Arabs, or from the ninth to the thirteenth century, geography was assiduously cultivated by them as a science, especially in Bagdad, the capital of the Caliphs, and for a part of that period in Spain. It is to the Arabians that we owe the preservation of the work of Ptolemy, which they translated into Arabic and annotated. They determined the obliquity of the ecliptic, measured two arcs of the meridian, ascertained more accurately the longitude of places in Asia and about the Mediterranean, and enlarged descriptive geography by an account of the countries in Asia over which they had extended their conquests. As early as the ninth century they trafficked in the ports of the Indian Ocean, and had intercourse also at that time with China, through which probably the mariner's compass was brought to the Mediterranean. I may also mention in this connection that the Chinese, according to the statements of their own writers, had maps from a very remote period. These are described as representing the mountains, seas, rivers, lakes, plains, and basins, and were compiled by order of the emperors.

The Arabian geographers prepared an elaborate work ( 830) founded upon Ptolemy. It is lost, but, from the references to it by Arab writers, we know that it gave a description of the habitable earth, and indicated the prominent places in different countries by their latitude and longitude, correcting, in the countries in which the Arabs were well acquainted, the gross errors in longitude of Ptolemy. It is from these tables of latitudes and longitudes that we know the wide extent of the geographical knowledge of the Arabs. Their corrections from west to east extended from Cadiz to the Indus, and they restored to their true position the places in the countries watered by the Euphrates and the Tigris. It is inferable, from statements of Arab writers, that they had maps constructed upon a mathematical basis.