Zhang Heng Seismoscope

Located in the Sheshan Seismic Station at the foot of West Sheshan Mountain, this museum features a theater hall, an earthquake information hall, an emergency rescue drill exhibit, and the Zhang Heng seismograph exhibition hall.

Zhang Heng was a Chinese scientist and mathematician from the Han Dynasty. Inside is a replica of his ancient seismoscope. During his life, it was still unknown that shifting tectonic plates caused earthquakes. Instead, earthquakes were explained as a disturbance in the cosmic yin and yang, along with the heavens' displeasure with the current dynasty. However, Heng believed earthquakes were actually caused by wind and air.

He invented his seismoscope in 132 CE. A seismoscope records disturbances along the earth's surface. The device Heng created was even able to roughly indicate the direction of an earthquake well over 100 miles away.

To indicate the direction of an earthquake, his device released a bronze ball from one of eight dragon heads. The ball then fell into the mouth of a corresponding toad below, each toad represented a direction similar to those on a compass. 

What makes his seismoscope so impressive is that modern replicas have all failed to reach the level of accuracy described in historical records. On one occasion, the device was triggered even though there was no evidence of a seismic event. Several days later, it was discovered that an earthquake had occurred in Longxi.