By the Han Dynasty, the Chinese developed various uses for the waterwheel. An improvement on the simple lever-and-fulcrum tilt hammer operated by a foot, the hydraulic-powered trip hammer was used for pounding, decorticating, and polishing grain and was first mentioned in the Han dictionary Ji Jiu Pian of 40 BCE. It was also mentioned many other works such as in the Regional Speech dictionary written by Yang Xiong in 15 BCE. In his Balanced Discourse, the philosopher Wang Chong first described the square-pallet chain pump that could pump water and other substances. Most chain pumps were powered by a horizontal waterwheel which rotated large toothed gears and a horizontal axis beam. Their primary use was for lifting water into irrigation ditches, but chain pumps were also used in public works programs, such as when Zhang Rang used them to lift water into pipes. The water was used to provide the capital Luoyang with clean water. While acting as administrator of Nanyang in 31 CE, Du Shi invented a water-powered reciprocator which utilized the bellows of the blast furnace and cupola furnace to smelt iron. Previously, intensive manual labor was required to work the bellows. Although the astronomical armillary sphere already existed in China since the 1st century BCE, the mathematician and court astronomer Zhang Heng provided it with motor power by using the constant pressure head of an inflow water clock to rotate a waterwheel. The wheel then acted on a set of gears, placing the sphere in motion. Zhang Heng also addressed the problem of the falling pressure head in the inflow water clock, which gradually slowed the timekeeping, by setting up an additional tank between the reservoir and inflow vessel.