Geodetic Meter - Chidogi

Japanese: 地動儀 - ちどうぎ

Properly called the Hou Feng Didong Yi, it is the world's oldest seismograph, invented in 132 (Yangjia 1) by Zhang Heng of the Eastern Han Dynasty in China. Made of copper, its shape resembles a wine jar, with a diameter of 8 shaku (1 shaku = 23 cm), and a dragon's mouth protruding in eight directions that holds a ball. When an earthquake occurs, the ball in the direction of the earthquake falls into the mouth of a toad (toad) below, which has its mouth open and faces upward, making a loud noise. Inside are cranks that can be turned in eight directions and a hook-and-loop device that is said to be used to communicate the displacement of an inverted pendulum in the center.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

正しくは候風地動儀といい，中国の後漢の張衡が132年(陽嘉1)に考案した世界最古の地震計。銅製で，外形は酒がめに似ており，直径は8尺(1尺＝23cm)，8方向に突起した竜口は球をくわえ，地震が起きると起こった方向にあたる球がその下で口を開けて上を向いたヒキガエル(蟾蜍)の口のなかに落ち，大きな音を発するようになっていた。内部は8方向に向かうクランクと掛外しの装置があり，中心の倒立振子の変位を伝える仕組みになっていたとされている。

出典　株式会社平凡社世界大百科事典第２版について　情報

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