A trip hammer, also known as a tilt hammer or helve hammer, is a massive powered hammer. Traditional uses of trip hammers include pounding, decorticating and polishing of grain in agriculture. In mining, trip hammers were used for crushing metal ores into small pieces, although a stamp mill was more usual for this. In finery forges they were used for drawing out blooms made from wrought iron into more workable bar iron. They were also used for fabricating various articles of wrought iron, latten (an early form of brass), steel and other metals. One or more trip hammers were set up in a forge, also known variously as a hammer mill, hammer forge or hammer works. The hammers were usually raised by a cam and then released to fall under the force of gravity. Historically, trip hammers were often powered hydraulically by a water wheel. Trip hammers are known to have been used in Imperial China since the Western Han dynasty. They also existed in the contemporary Greco-Roman world, with more evidence of their use in medieval Europe during the 12th century. During the Industrial Revolution the trip hammer fell out of favor and was replaced with the power hammer. Often multiple hammers were powered via a set of line shafts, pulleys and belts from a centrally located power supply. Early history China In ancient China, the trip hammer evolved out of the use of the mortar and pestle, which in turn gave rise to the treadle-operated tilt-hammer (Chinese: 碓 Pinyin: dui; Wade-Giles: tui). The latter was a simple device employing a lever and fulcrum (operated by pressure applied by the weight of one's foot to one end), which featured a series of catches or lugs on the main revolving shaft as well. This device enabled the labor of pounding, often in the decorticating and polishing of grain, and avoided manual use of pounding with hand and arm. Although Chinese historians assert that its origins may span as far back as the Zhou Dynasty (1050 BC–221 BC), the British sinologist Joseph Needham regards the earliest texts to describe the device are the Jijiupian dictionary of 40 BC, Yang Xiong's text known as the Fangyan of 15 BC, as well as the "best statement" the Xin Lun written by Huan Tan about 20 AD (during the usurpation of Wang Mang). The latter book states that the legendary mythological king known as