Seismic waves are the vibrations from earthquakes that travel through the Earth; they are recorded on instruments called seismographs. The first crude seismograph was the dragon jar. The dragon jar was a cylindrical jar with eight dragonheads arranged around its brim; each dragon had a ball in its mouth. Around the foot of the jar were eight frogs, each directly under a dragonhead. When an earthquake happened a ball dropped from a dragon's mouth and was caught by the frog's mouth. Photo credit: LOC