英语翻译Early in the century,a pump hadcome into use in which expanding steam raised a piston in a cylinder,andatmospheric pressure brought it down again when the steam condensed inside thecylinder to form a vacuum．

本世纪早期，泵开始使用，膨胀的蒸汽在汽缸中抬升一个活塞，当蒸汽在汽缸中冷凝时气压又将活塞压下来，从而形成气缸内真空。
Early in the century 时间状语
a pump had come into use 主句
in which... 定语从句，形容pump的工作原理

Early in the century,（ 时间状语 ，翻译这个世纪早期） a pump had come into use 泵早被使用了 （ 是主句）in which expanding steam raised a piston in a cylinder,膨胀的气体在汽缸中上升一个活塞 and atmospheric pressure brought it down again 而且大气压又使其下降 when the steam condensed inside the cylinder to form a vacuum．当气体在气缸内压缩形成真空的时候。 （ 时间状语从句） （in which ... 定语从句,修饰pump)
本世纪世纪初期， 泵已投入使用，当气体在气缸内压缩形成真空的时候， 泵里膨胀的气体在汽缸中会上升一个活塞而且大气压又会使其下降。

时间状语: Early in the century, 主语:a pump + 谓语:had come into use 从in which .句末: 定语从句修饰use in which =in use 在使用中 定从中含有一个并列句: 分句1: expanding steam(主语)+ raised a piston ...