Yeong-sil Jang (Unknown)

  • Moon-Hyon NamEmail author
Part of the History of Mechanism and Machine Science book series (HMMS, volume 26)


Yeong-sil Jang (called Jang Yeong-sil in the Korean style, Unknown) was a Korean inventor and mechanical engineer who served as chief court engineer under King Sejong of the Joseon dynasty (AD 1392–1910). He made two Striking Clepsydras (Jagyeong-nu) in the course of equipping the Royal Observatory in AD 1432–38. He invented liquid-driven discrete ball-falling mechanisms and ball-driven discrete motion control mechanisms for operating dual-time-announcing devices, and applied these towards making the Striking Palace Clepsydra. He developed the mechanisms and employed them to make a functional astronomical clock, the Striking Heavenly Clepsydra, which worked in conjunction with a water-powered wheel drive. The clepsydra was a standard timekeeper capable of announcing twelve double-hours with a bell simultaneous with a visual display indicating the current time. Five night-watches and their twenty-five points could also be announced by way of a drum and gong without human involvement. The stories of his works are told in the Annals of Sejong issued in 1454 and are supplemented by accounts in the dynastic documents afterwards. His innovations on mechanism design led to subsequent astronomical clocks from the seventeenth century onwards in Korea. Not only did he assimilate the techniques of his Korean, Chinese and Islamic predecessors, but was also creative and innovative in the history of mechanism and machine design.


Copper Plate Copper Tube Short Tube Royal Observatory Night Watch 
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The author wishes to thank the National Palace Museum of Korea in Seoul, Sang-huh Memorial Library and the Museum, members of the Research Center for the Korean History of Technology of Konkuk University, Professors Young-ho Hahn, Moon-hwo Seo, Jai-hyo Lee, Sung-kyun Kim (former) Ministry of Science and Technology of Korea, Institute for History of Natural Science of Academia Sinica, Asan Jang Society, and Young-si Lee, Sin-ku Kang, Yong-geun Kim, Yong-sun Hong (author’s wife) and members of the Jagyeongnu Research Institute, Curator Joon Seo of the National Palace Museum of Korea, the late eminent mechanist Bong-ryong Jeong, Master Craftsmen Gwang-sik Won and Gyo-jun Choe, Master Carpenters Gwang-bok Lee and brothers Jin-hyeong and Nam-hyeong Lee who collaborated in the reconstruction of the Striking Palace Clepsydra from 2004–2005. Thanks also to Professor Dr. Yoonkey Nam at the Korean Advanced Institute of Science and Technology (KAIST) for reviewing the manuscript.


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Further Reading

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  3. Nam MH (2011) Reconstruction of a Striking Clepsydra of Joseon period of King Sejong. In: Nakamura T, Orchiston W, Sôma M, Strom R (eds) Mapping the Oriental Sky, Proceedings Seventh International Conference Oriental Astronomy (ICOA-7), pp 116–125, Tokyo, National Astronomical Observatory of JapanGoogle Scholar
  4. Needham J, Wang L (1965) Science and civilisation in China (SCC), vol IV-pt.2, pp 517–518Google Scholar
  5. Yan HS (2007) Reconstruction designs of lost ancient Chinese machinery. Springer, DordrechtCrossRefzbMATHGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  1. 1.Konkuk University and Jagyeongnu Research InstituteSeoulSouth Korea

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