朝鮮의 更漏法

Abstract

The operation system for a night-watch clepsydra had been comprised of The Principle of Clepsydra Indicator-Rods (漏籌通義) and accompanying Records of Culminating Stars (中星記). The indicator-rod manual specified the way to combine the scales of night-watch(更) and its division(點) upon the graduations of hour(時) and interval(刻), because the spacing of night-watch varies from rod to rod due to the seasonal change of day/night apportionment. The guide manual also stated available term for each rod and rod-shifting date throughout a year. The culminant stars were used as references to validate the night time on the graduation of clepsydra rod by confirming whether the star or constellation corresponding to the night-watch was crossing the meridian or not. Soon after the foundation of the dynasty and the transfer of the capital to Hanyang, King Taejo (r. 1392-98) had established the first night-watch system with 21 indicator-rods and carved a new culminating star list on a stone star map. During Chosun dynasty the system of the clepsydra had been reformed three times. With the advent of The Striking Clepsydra (自擊漏) the number of floating indicator-rods changed to eleven in 1434 by King Sejong (r. 1418-1450), then to twenty four in mid-18th century during King Yeongjo's reign (1724-1776), and finally to thirty seven in 1789 under the rule of King Jeongjo (1776-1800). In this paper the definite structures of the successive four night-watch systems were analyzed numerically and investigated bibliographically into details. The background of rod number and operating terms of rods for each system were searched and revealed. The culminant star charts were recalculated to find out the entity now forgotten and to check the accuracy it had.