Heng, Zhang

December 10, 2010, 4:55 pm

Zhang Heng (78 A.D.-139 A.D.), a Chinese mathematician and scientist who lived during the Han Dynasty. Heng is thought to have built the first seismoscope or seismometer in A. D. 132.

caption A model of Heng's seismoscope

The device worked on the principle of inertia wherein a mass is suspended. An earthquake shakes the vessel, causing a slight displacement between the mass and the vessel; this movement is transmitted via levers and gears to push out a ball. The surface of the vessel was decorated with motifs of mountains, tortoises, birds, animals, and antique writing. Around the vessel were eight dragons whose mouths held a ball. Around the base of the vessel sat eight corresponding toads with their mouths open, looking upwards. The sign for an earthquake was the falling of a ball from the dragon into the mouth of a toad. The direction of the earthquake was indicated by the position of the toad that swallowed the ball.

Further Reading

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Citation

Cleveland, C. (2010). Heng, Zhang. Retrieved from http://www.eoearth.org/view/article/153476

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