It was practical books about fortifications, hydraulics, artillery, navigation, and shipbuilding.

而是实际的书籍,比如有关防御工事的,水力学,炮术,航海和造船的

耶鲁公开课 - 欧洲文明课程节选

They were robots powered by hydraulics.

当时的机器人需要用水力来带动

耶鲁公开课 - 心理学导论课程节选