1883年，米尔恩（JOHN MILNE）在其专著《地震和地球的其它运动》（EARTHQUAKES AND OTHER EARTH MOVEMENTS）中，把《后汉书∙张衡传》翻译成英文。

 《后汉书∙张衡传》原文如下：

  阳嘉元年，复造候风地动仪。以精铜铸成，员径八尺，合盖隆起，形似酒尊，饰以篆文山龟鸟兽之形。中有都柱，傍行八道，施关发机。外有八龙，首衔铜丸，下有蟾蜍，张口承之。其牙机巧制，皆隐在尊中，覆盖周密无际。如有地动，尊则振龙，机发吐丸，而蟾蜍衔之。振声激扬，伺者因此觉知。虽一龙发机，而七首不动，寻其方面，乃知震之所在。验之以事，合契若神。自书典所记，未之有也。尝一龙机发而地不觉动，京师学者咸怪其无征。后数日驿至，果地震陇西，于是皆服其妙。自此以后，乃令史官记地动所从方起。

 米尔恩的英文翻译如下：

   ‘In the first year of  Yōka, A.D. 136, a Chinese called Chôko invented the seismometer shown in the accompanying drawing. This instrument consists of a spherically formed copper vessel, the diameter of which is eight feet. It is covered at its top, and in form resembles a wine-bottle. Its outer part is ornamented by the figures of different kinds of birds and animals, and old peculiar-looking letters. In the inner part of this instrument a column is so suspended that it can move in eight directions. Also, in the inside of the bottle, there is an arrangement by which some record of an earthquake is made according to the movement of the pillar. On the outside of the bottle there are eight dragon heads, each of which holds a ball in its mouth. Underneath these heads there are eight frogs so placed that they appear to watch the dragon's face, so that they ready to receive the ball if it should be dropped. All the arrangements which cause the pillar to knock the ball out of the dragon's mouth are well hidden in the bottle. ’

  'When an earthquake occurs, and the bottle is shaken, the dragon instantly drops the ball, and the frog which receives it vibrates vigorously; any one watching this instrument can easily observe earthquake. '

  With this arrangement, although one dragon may drop a ball, it is not necessary for the other seven dragons to drop their balls unless the movement has been in all directions; thus we can easily tell the direction of an earthquake.

  'Once upon a time a dragon dropped its ball without any earthquake being observed, and the people therefore thought the instrument of no use, but after two or three days a notice came saying that an earthquake had taken place at Rōsei. Hearing of this, those who doubted the use of this instrument began to believe in it again. After this ingenious instrument had been invented by Chôko, the Chinese Government wisely appointed a secretary to make abservations on earthquakes. '