Han Dynasty scientist Zhang Heng seismograph is another masterpiece of masterpieces. Zhang Heng in the Eastern Han dynasty which, more frequent earthquakes. According to the "Han Five Elements" records from Dili Yongyuan four years (AD 1992) to 安帝延 light four years (AD 125 years) of thirty years, a total of two sixth major earthquake. Sometimes big earthquake zone to dozens of counties, cause to crack landslides, flooding rivers, houses collapsed, causing huge losses. Zhang Heng, a lot of experience on the earthquake. In order to grasp the National Seismology, after years of research he finally Yang Jia in the first year (132 AD) invented the seismograph ── a world's first seismograph. After communication developed in ancient times, earthquake, earthquake time to know people and to determine the general location of earthquakes have a certain role. According to the "Han Zhang Heng Chuan" records, seismograph "to refined copper cast, eight feet diameter circle", "shape Jiuzun" has the appearance of a raised circle on the cover of the instrument as well as engraved Zhuanwen Hill, turtles, birds , animals and other graphics. Inside there is a central instrument of brass "are the column" retrofitting has eight channels, known as the "eight, as well as a clever machine, off external body around eight bottles a leader, according to the East, South, West, North, eight directions southeast, northeast, southwest, northwest cloth out. connected to the leading and internal organs of the channel launch, each leading his mouth title has a copper ball, facing the leading eight toad squatting on the ground, all Angtou mouth, ready to undertake the copper ball. When an earthquake somewhere, along with bottles of body movement, touch organs, so that the direction of the earthquake's leading open his mouth, spit out the copper ball, fell to the toad's mouth, change a lot sound, so people can know the direction of the earthquake.