GARY HINCKS / SCIENCE PHOTO LIBRARY GARY HINCKS / SCIENCE PHOTO LIBRARY
Chinese earthquake detector, artwork. This device was invented around 132 A.D., by Zhang Heng. It consists of a copper-domed urn with dragons' heads circling the outside, each containing a bronze ball, and a pendulum hung from its top inside. When the Earth shook, the pendulum would swing, knocking a ball from one of the dragon heads into the open mouth of a bronze toad below. The direction of the earthquake's epicentre could be determined from which ball had been released.
Model release not required. Property release not required.