The Chinese enjoyed a triple advantage, by means of which they were enabled to enrich their earliest literature with so considerable an amount of orographic knowledge regarding Upper Asia, and more especially those regions situated between the In-schan, the alpine lake of Khuku-noor, and the shores of the Ili and Tarim, lying north and south of the Celestial Mountains, and which were so little known to Western Europe. These three advantages were, besides the peaceful conquests of the Buddhist pilgrims, the warlike expeditions towards the west (as early as the dynasties of Han and Thang, one hundred and twenty-two years before our era, and again in the ninth century, when conquerors advanced as far as Ferghana and the shores of the Caspian Sea); the religious interest attached to certain high mountain summits, on account of the periodical performance of sacrifices, in accordance with pre-existing enactments; and lastly, the early and generally known use of the compass for determining the direction of mountains and rivers. This use, and the knowledge of the south-pointing of the magnetic needle, twelve centuries before the Christian era, gave a great superiority to the orographic and hydrographic descriptions of the Chinese over those of Greek and Roman authors, who treated less frequently of subjects of this nature. The acute observer Strabo was alike ignorant of the direction of the Pyrenees and of that of the Alps and Apennines.[BE]