WITH the Sung dynasty firmly established in 960 A.D., the Chinese Empire entered upon a long period of prosperity rendered glorious by the cultivation of the arts of peace. It is true that the boundaries of the Empire were contracted and the Tartar tribes on the north-west had made good their independence and remained a constant menace to the frontiers of China. In 1127 the dam was broken and the desert warriors, no longer to be kept in check by diplomacy or force, burst upon Northern China and drove the peace-loving Sung from their capital, the modern K´ai-fêng Fu in Honan. The Emperor Kao Tsung and his Court fled across the Yangtze to their new capital at Hang Chou, where the dynasty continued under the name of the Southern Sung until 1279. The description given by Marco Polo of Hang Chou, which he considered, even in 1280, to be "beyond dispute the finest and the noblest city in the world," presents a wonderful picture of the refinement and luxury of the Sung civilisation. The great city had its network of canals and its twelve thousand stone bridges, its flourishing guilds of craftsmen, its merchant princes who lived "nicely and delicately as kings," its three hundred public baths of hot water, its ten principal markets, its great lake lined with houseboats and barges, and its streets thronged with carriages. The citizens themselves were peaceful and orderly, neither wearing arms nor keeping them in their homes, and their cordiality to foreigners was hardly less than the good will and friendliness which marked their relations to one another.