《新仪象法要》中的“铁鹤膝”考释

A Research on the"Iron Crane Knee"in Hsin I Hsiang Fa Yao

作为水运仪象台的关键部件,“铁鹤膝”的结构功能至今未获定论。通过对既有说法的考据和对《新仪象法要》的解读,可以认定“铁鹤膝”既不是李约瑟所设想的“铁链”,也不是其他学者所推测的“弹簧-直杆”或“X-金属条”。从“鹤膝”在军事、植物、医学、家具、书法、格律、农业等诸多语境中的使用和水运仪象台众多部件出自农业机械的情况来看,“铁鹤膝”最有可能源于农业机械--龙骨车的部件“鹤膝”。结构上,“铁鹤膝”是由单个铁制“鹤膝”串接形成的链条,可根据需要调整长度。功能上,“铁鹤膝”连接关舌与天衡,在关舌被击开后拉动天衡、打开天关和左天锁,使枢轮得以运转。

As a key component of the the Su-song's Clock-tower,the structure and function of the"iron crane knee"(celestial rod)has not yet been determined.Through the examination of the existing claims and the interpretation of Hsin I Hsiang Fa Yao,it can be concluded that the"iron crane knee"is neither the"iron chain"envisioned by Joseph Needham,nor the"spring-rod"or"X-rod"speculated by other scholars.From the rules of using"crane knee"in many contexts such as military,plant,furniture,medical,metrical,calligraphic,and agricultural contexts,and from the fact that many parts of the Su-song's Clock-tower came from agricultural machinery,it is most likely that"iron crane knee"originated from Dragon-bone Pump.Structurally,the"iron crane knee"is a chain formed by stringing individual iron"crane knees"together,and the length can be adjusted as needed.Functionally,the"iron crane knee"connects the trip-lever to the upper balancing lever,and after the trip-lever opened,the upper balancing lever is pulled,and the upper stop and left upper lock are opened,allowing the the driving-wheel to operate.