<P> The economic power of Song China heavily influenced foreign economies abroad . The Moroccan geographer al - Idrisi wrote in 1154 of the prowess of Chinese merchant ships in the Indian Ocean and of their annual voyages that brought iron, swords, silk, velvet, porcelain, and various textiles to places such as Aden (Yemen), the Indus River, and the Euphrates in modern - day Iraq . Foreigners, in turn, affected the Chinese economy . For example, many West Asian and Central Asian Muslims went to China to trade, becoming a preeminent force in the import and export industry, while some were even appointed as officers supervising economic affairs . Sea trade with the South - west Pacific, the Hindu world, the Islamic world, and East Africa brought merchants great fortune and spurred an enormous growth in the shipbuilding industry of Song - era Fujian province . However, there was risk involved in such long overseas ventures . In order to reduce the risk of losing money on maritime trade missions abroad, wrote historians Ebrey, Walthall, and Palais: </P> <P> (Song era) investors usually divided their investment among many ships, and each ship had many investors behind it . One observer thought eagerness to invest in overseas trade was leading to an outflow of copper cash . He wrote,' People along the coast are on intimate terms with the merchants who engage in overseas trade, either because they are fellow - countrymen or personal acquaintances...(They give the merchants) money to take with them on their ships for purchase and return conveyance of foreign goods . They invest from ten to a hundred strings of cash, and regularly make profits of several hundred percent' . </P> <P> Advancements in weapons technology enhanced by gunpowder, including the evolution of the early flamethrower, explosive grenade, firearm, cannon, and land mine, enabled the Song Chinese to ward off their militant enemies until the Song's ultimate collapse in the late 13th century . The Wujing Zongyao manuscript of 1044 was the first book in history to provide formulas for gunpowder and their specified use in different types of bombs . While engaged in a war with the Mongols, in 1259 the official Li Zengbo wrote in his Kezhai Zagao, Xugaohou that the city of Qingzhou was manufacturing one to two thousand strong iron - cased bomb shells a month, dispatching to Xiangyang and Yingzhou about ten to twenty thousand such bombs at a time . In turn, the invading Mongols employed northern Chinese soldiers and used these same types of gunpowder weapons against the Song . By the 14th century the firearm and cannon could also be found in Europe, India, and the Islamic Middle East, during the early age of gunpowder warfare . </P> <P> As early as the Han dynasty, when the state needed to accurately measure distances traveled throughout the empire, the Chinese relied on a mechanical odometer . The Chinese odometer was a wheeled carriage, its gearwork being driven by the rotation of the carriage's wheels; specific units of distance--the Chinese li--were marked by the mechanical striking of a drum or bell as an auditory signal . The specifications for the 11th century odometer were written by Chief Chamberlain Lu Daolong, who is quoted extensively in the historical text of the Song Shi (compiled by 1345). In the Song period, the odometer vehicle was also combined with another old complex mechanical device known as the south - pointing chariot . This device, originally crafted by Ma Jun in the 3rd century, incorporated a differential gear that allowed a figure mounted on the vehicle to always point in the southern direction, no matter how the vehicle's wheels turned about . The concept of the differential gear that was used in this navigational vehicle is now found in modern automobiles in order to apply an equal amount of torque to a car's wheels even when they are rotating at different speeds . </P>

Who restored the power of china in east asia