by gold and silver stores, the Song Dynasty government initiated a nationwide paper currency, between 1265 and 1274. The concurrent Jin Dynasty (1115–1234) also printed paper banknotes by at least 1214. Bellows, hydraulic-powered: Although it is unknown if metallurgic bellows (i.e. air-blowing device) in the Han Dynasty (202 BC – 220 AD) were of the leather bag type or the wooden fan type found in the later Yuan Dynasty (1279–1368), the Eastern Han dynasty mechanical engineer and politician Du Shi (d. 38 AD) applied the use of rotating waterwheels to power the bellows of his blast furnace smelting iron, a method which continued in use in China thereafter, as evidenced by subsequent records; it is a significant invention in that iron production yields were increased and it employed all the necessary components for converting rotary motion into reciprocating motion. Belt drive: The mechanical belt drive, using a pulley machine, was first mentioned in the text the Dictionary of Local Expressions by the Han Dynasty philosopher, poet, and politician Yang Xiong (53–18 BC) in 15 BC, used for a quilling machine that wound silk fibers on to bobbins for weavers' shuttles. The belt drive is an essential component to the invention of the spinning wheel. The belt drive was not only used in textile technologies, it was also applied to hydraulic powered bellows dated from the 1st century AD. Belt hook: The belt hook was a fastener used in China. Belt hooks date to the 7th century BC in China, and were made with bronze, iron, gold, and jade. Texts claim that the belt hook arrived in China from Central Asia during the Warring States period, but archaeological evidence of belt hooks in China predate the Warring States Period. Biological pest control: The first report of the use of an insect species to control an insect pest comes from "Nan Fang Cao Mu Zhuang" (南方草木狀 Plants of the Southern Regions) (ca. 304 AD), attributed to Western Jin dynasty botanist Ji Han (嵇含, 263–307), in which it is mentioned that "Jiaozhi people sell ants and their nests attached to twigs looking like thin cotton envelopes, the reddish-yellow ant being larger than normal. Without such ants, southern citrus fruits will be severely insect-damaged". The ants used are known as huang gan (huang = yellow, gan = citrus) ants (Oecophylla smaragdina). The practice was later reported by Ling Biao Lu Yi (late Tang Dynasty