The World’s First Seismograph - The Dragon Jar

• The first known measuring instrument was invented around 132 A.D. during the Han Dynasty by a Chinese philosopher and scientist named Zhang Heng, who was from the Henan province. The instrument was called the “Houfeng Didong Yi” or the “dragon jar” which was a bronze jar or urn with a central pendulum inside. Eight dragonheads surround the exterior of the jar. The pendulum is connected to eight levers where each lever leads to a dragonhead.
• Each of the dragon has a bronze ball in its mouth and directly beneath each dragon was a open-mouthed frog at the base of the jar. The earth tremors will trigger the pendulum to hit one of the arms causing that specified dragon to split out its ball.The direction of the earthquake was indicated by which dragon had dropped a ball.
• It is recorded that his ingenious invention detected an earthquake in February in the year 138 about 600 kilometers away from Luoyang, then China’s capital, according to the History of the Later Han, an official Chinese historial record.
• The original dragon jar did not survive history. It was first reconstructed by a Japanese scholar in 1875 based on the description about the device in Zhang’s biography in the History of the Latter Han and archaeological research findings. Another well-known model was redesigned by a Chinese museum researcher Wang Zhenduo in 1951. However none of the replicas could detect any termors.
• On June 13, 2005, Chinese seismologists and archeologists from the Chinese Academy of Sciences, the National Museum and China Earthquake Administration announced that they had successfully created a replica of the instrument, one that works.

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