Miles

    The Dragon & Toad Seismograph was invented in 132 AD. It was invented in Ancient China during the Han Dynasty by Zhang Heng, the director of astrology in the late Han court. It was invented to keep track of the earthquakes that occurred in China.

    This seismograph is a big and intricate invention. It is made up of a great bronze jar with a domed cover. It is 1.84 meters in diameter. The decorations on the outside of the jar are mountains, tortoises, and other animals. Around the jar, there are eight toads with their mouths open. Above each of those toads, there is a dragon head sticking out with balls in their mouths. Inside, there is a central column or pendulum in the middle and 8 grooves that end in each dragon head. In each groove, there is a rod trigger ending in the mouth of the dragon.

    The seismograph is used for locating earthquakes. When an earthquake occurred, the pendulum would fall into a groove and hit the rod. The rod knocked the balls out of the dragon's mouth and into the toad. The direction of the site of the earthquake is determined by the direction of the toad that the ball fell into. The Dragon & Toad located an earthquake that occurred in Longxi in the Kansu province.

    In addition to finding the direction of the earthquake, modem seismographs can also measure the strength of the earthquake. This seismograph is a weight attached to a metal frame with a spring. When the frame moves with the ground, the weight does not move. When the frame stops moving, the weight moves and draws the movement with a pen attached to the moving weight.

    The Dragon & Toad Seismograph is an extremely clever instrument. It triggers with the slightest movement from far-off earthquakes. It is wonderfully balanced and smartly made. It never gives off false alarms. 

1. Anderson, John G. "Seismographs." World Book Encyclopedia. 1991.

2. Annento, Beverly J. A Message of Ancient Days. Boston: Houghton Mifflin Company, 1994.

3. Beshore, George. Science In Ancient China. New York: Franklin Watts, 1988.

4. Merson, John. The Genius That Was China. Woodstock: The Overlook Press, 1990.

5. Schafer, Edward H. Ancient China. Canada: Time Life Books, 1967.

6. Serstevens, Michelle P. The Han Dynasty. New York: Rizzoli, 1982.