The Southern Song dynasty (1127-1200), turned China into a seagoing nation. Instead of the outposts along the Old Sild Roads, the coastal ports of east China became the main points of contact between the Central Kingdom and the outside world.
Improvements in navigation fostered the growth of Chinese sea trade. The Chinese first used the compass in the early 1100s, decades before it appeared in Europe. Chinese merchant ships sailed to Southeast Asia, India, the East Indies, and later as far as Africa.
Other developments fueled the explosion of trade. The Yangtze Valley and southern China generally have better farmlands and more rainfall than northern China. The central and southern provinces were the best rice, silk, and tea producers. Silk and tea, especially, were greatly prized by the rest of the world. The Southern Sung printed paper money and invented the world's earliest calculator--the abacus. Cities mushroomed in size. Hangchou alone had a population of two million. For the first time in history, the main source of government income shifted from the land to the cities. There was more money to be made taxing silk, tea, pottery, and other imports and exports than there was from taxing grain.