Model of the Zhang Heng seismoscope
- 132 CE
- Zhang Heng
Model of Chang Heng seismoscope, 132AD, cut away to show internal mechanism
The Chinese astronomer, mathematician and seismologist, Zhang Heng (78-139 AD) described the earliest seismoscope known in about 132 AD. Arriving shock waves displace a pendulum linked to a mechanism which opens the jaws of the dragon facing the direction of the earthquake. A ball falls from the dragon's teeth into the mouth of a toad below to record the event.