東漢時期，地震頻繁發生。通過對地震的一系列仔細觀測，張衡于公元132年發明了地動儀(seismograph)，它是世界上第一個用來識別和確定地震方向的儀器。 地動儀表面上鑄(cast)有八條龍，每一條龍的嘴里都有一個銅球。八條龍身下的地面上有八只仰著頭的銅蟾蜍(toad)，銅蟾蜍張著的嘴恰與龍口相對。當地震發生時，面朝地震方向的龍口會張開，口中的球將落入蟾蜍的嘴里，自動指明地震的方向。

　　During the Eastern Han period，earthquakesoccurred frequently. Through a series of carefulobservations of earthquakes，Zhang Heng inventedthe seismograph ,in 132 AD, which was the world'sfirst instrument to identify and ascertain thedirection of earthquakes. The seismograph is cast with eight dragons on the surface,and eachdragon has a copper ball in the mouth. On the ground below the dragons there are eightcopper toads raising their heads and opening their mouths opposite to the dragons'mouths.When an earthquake occurred, the dragon facing the direction of the earthquake would openits mouth，and the ball in its mouth would fall into the toad's mouth, automatically indicatingthe direction of the earthquake.

　　絲綢之路(the Silk Road)是世界上最偉大、最重要的貿易通路之一。它是連接中國和歐洲、東方和西方的陸路通道。絲綢之路始于公元前2世紀，漢高祖(Han Emperor)派遣張騫出使西域的時期。絲綢之路極其分散，很少有商人走過整個道 路。大部分地區地形崎嶇或有敵對勢力的存在，使得絲綢之路非常危險。因此絲 綢和其他商品的供應經常受到限制。

　　The Silk Road is one of the greatest and mostimportant trade routes. It is the overland route thatconnects China and Europe, the East and the West.The Silk Road began in the 2nd century BCE whenHan Emperor gave Zhang Qian the diplomaticmissions of visiting the Western regions. The Silk Road was largely scattered and very fewmerchants ever crossed the whole route. Most of the areas along the road were rugged or withhostile forces, which made the route quite dangerous. Therefore, the supply of silk and othergoods was often limited.