Seismometer

The seismograph is an ancient measuring instrument created by Zhang Heng, a scientist in the Eastern Han Dynasty of China. The seismograph has eight orientations, which are east, south, west, north, southeast, southwest, northeast, and northwest. Each orientation has a dragon head containing a dragon ball, and there is a toad corresponding to it under each dragon head. If an earthquake occurs on either side, the dragon ball contained in the dragon's mouth in that direction will fall into the toad's mouth, and the direction of the earthquake can be determined from this.