mercury line

例句：

1. 1. The mercury line is a symbol of the city's prosperity.
   水银线是这座城市繁荣的象征。
2. 2.The mercury line was used to measure the depth of the ocean.
   水银线用于测量海洋的深度。
3. 3.The mercury line has been used for centuries as a means of communication.
   水银线作为一种通信手段，已经使用了好几个世纪。